January 18 2006 IAP 2006 12091Session 3A P ILA

MEDICALGEOLOGYGEOCHEMISTRY

PILLALAMARRI ILA

Earth Atmospheric amp Planetary SciencesNeutron Activation Analysis LaboratoryMassachusetts Institute of Technology

Cambridge MA 02139IAP 2006 12091 Credit Course January 9 - 23 2006

Session 3A - January 18 2006

January 18 2006 IAP 2006 12091Session 3A P ILA

Session 3 January 18 2006Objective

Session 3AOverview of Analytical Techniques

Atomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe ‐ Wavelength and EnergyDispersive X‐ray Spectroscopy

Session 3B11AM‐12PM

(EAPS ‐ Neutron Activation Analysis Laboratory)Concepts of Sample PreparationHands on Experience with instruments forTrace Element Determination by NeutronActivation Analysis ndashHand out of review quiz

January 18 2006 IAP 2006 12091Session 3A P ILA

IntroductionAnalytical technique is a tool to determinebull abundances of elementsbull information about mineralsbull information about organics

May be categorized asbull inorganic and organicbull qualitative and quantitativebull spectroscopic and classical

January 18 2006 IAP 2006 12091Session 3A P ILA

Introduction hellipbull Qualitative means ndash identificationbull Quantitative means - determining theabundanceThe basic concept of quantitative analysisTake a material with known abundances calledthe standardUsing the known amount of abundance(s) in thestandard estimate the abundance(s) in theunknown called the sample maintaining all theconditions and parameters same for the sampleand the standard

January 18 2006 IAP 2006 12091Session 3A P ILA

Spectroscopic vs Classical Techniquesbull Spectroscopic analytical techniques utilizeelectromagnetic radiation interaction with thematerials for analysisbull Classical techniques utilize physical propertiescolor conductivity densityelectric charge massrefraction volume

January 18 2006 IAP 2006 12091Session 3A P ILA

Electromagnetic Radiation ndashSpectroscopic Techniques

Electromagnetic radiation consistsof two sinusoidal waveforms namely electric and magneticpropagated along the same axisin planes perpendicular to eachotherThe electromagnetic wave hastwo propertiesEnergy EWavelength λ (or frequency υ)E = hc λ = hυh is Planckrsquos constantc is velocity of lightLight is a well known example ofelectromagnetic radiation

The blue curve indicates the electric vector and orange curvethe magnetic vector component

Figure by MIT OCW

Figure 1 Components of electromagnetic radiation

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 2 Calibration Curve

Quantitative analysisinvolvesdetermination of acalibration curve bymeasuring theanalytical signal as afunction of knownconcentrations of thestandard(s) conductedin a range of values

Figure 2 Calibration curve for quantitative analysis

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 3Electromagnetic Spectrum and Spectroscopic

Techniques

Based on Figure 31 pp 78 A Handbook of Silicate Rock Analysis P J Potts

January 18 2006 IAP 2006 12091Session 3A P ILA

Spectroscopic Techniques hellip

bull The different energies of the photons in theelectromagnetic spectrum are representative ofdifferent types of interactions in the atoms andmolecules and are detected and measured bydifferent types of spectroscopic techniquesbull Microwave and infrared spectroscopy use theproperties of molecular rotations andvibrationsbull Ultra violet and visible light spectroscopy utilizeabsorption and emission of energies of outerelectron transitionsbull X-ray fluorescence ndash inner electronsbull Gamma rays ndash nuclear transitions

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4APictorial depiction of Atomic Nucleus ndash Electron

Orbitals

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4BAtomic Absorption and Emission

Excited State

Ground State

Absorption Emission

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic SpectroscopyAtomic Absorption and Atomic Emission

PrinciplesAtomic spectra are generatedby transitions of electronsfrom one discrete orbital toanother in an atom The difference in energybetween respective orbitalscorresponds to the energyof the electromagneticradiation in the UV-VisibleregionTwo processes namelyabsorption and emissionprovide analytical capability

Excited State

Ground State

AbsorptionEmission

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Technique

This technique was developed out of thephenomenon ndash observation of the spectrallines of solar radiationThe understanding of this observation is that(the spectral lines) the observed spectrum isdue to the absorption of light in the atomicvapor in the Sunrsquos atmosphere - Discovery inthe 1925sStrong absorption of optical radiation by atomsof an element could be induced if the samplewere excited by the atomic radiation of thatelement

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption hellip

Simple explanation

Induced radiation of the element excites thesample material causing excitement of theelectrons of the specific element from lower tohigher orbitals

Absorbs radiation from the sample

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Session 3 January 18 2006Objective

Session 3AOverview of Analytical Techniques

Atomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe ‐ Wavelength and EnergyDispersive X‐ray Spectroscopy

Session 3B11AM‐12PM

(EAPS ‐ Neutron Activation Analysis Laboratory)Concepts of Sample PreparationHands on Experience with instruments forTrace Element Determination by NeutronActivation Analysis ndashHand out of review quiz

January 18 2006 IAP 2006 12091Session 3A P ILA

IntroductionAnalytical technique is a tool to determinebull abundances of elementsbull information about mineralsbull information about organics

May be categorized asbull inorganic and organicbull qualitative and quantitativebull spectroscopic and classical

January 18 2006 IAP 2006 12091Session 3A P ILA

Introduction hellipbull Qualitative means ndash identificationbull Quantitative means - determining theabundanceThe basic concept of quantitative analysisTake a material with known abundances calledthe standardUsing the known amount of abundance(s) in thestandard estimate the abundance(s) in theunknown called the sample maintaining all theconditions and parameters same for the sampleand the standard

January 18 2006 IAP 2006 12091Session 3A P ILA

Spectroscopic vs Classical Techniquesbull Spectroscopic analytical techniques utilizeelectromagnetic radiation interaction with thematerials for analysisbull Classical techniques utilize physical propertiescolor conductivity densityelectric charge massrefraction volume

January 18 2006 IAP 2006 12091Session 3A P ILA

Electromagnetic Radiation ndashSpectroscopic Techniques

Electromagnetic radiation consistsof two sinusoidal waveforms namely electric and magneticpropagated along the same axisin planes perpendicular to eachotherThe electromagnetic wave hastwo propertiesEnergy EWavelength λ (or frequency υ)E = hc λ = hυh is Planckrsquos constantc is velocity of lightLight is a well known example ofelectromagnetic radiation

The blue curve indicates the electric vector and orange curvethe magnetic vector component

Figure by MIT OCW

Figure 1 Components of electromagnetic radiation

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 2 Calibration Curve

Quantitative analysisinvolvesdetermination of acalibration curve bymeasuring theanalytical signal as afunction of knownconcentrations of thestandard(s) conductedin a range of values

Figure 2 Calibration curve for quantitative analysis

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 3Electromagnetic Spectrum and Spectroscopic

Techniques

Based on Figure 31 pp 78 A Handbook of Silicate Rock Analysis P J Potts

January 18 2006 IAP 2006 12091Session 3A P ILA

Spectroscopic Techniques hellip

bull The different energies of the photons in theelectromagnetic spectrum are representative ofdifferent types of interactions in the atoms andmolecules and are detected and measured bydifferent types of spectroscopic techniquesbull Microwave and infrared spectroscopy use theproperties of molecular rotations andvibrationsbull Ultra violet and visible light spectroscopy utilizeabsorption and emission of energies of outerelectron transitionsbull X-ray fluorescence ndash inner electronsbull Gamma rays ndash nuclear transitions

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4APictorial depiction of Atomic Nucleus ndash Electron

Orbitals

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4BAtomic Absorption and Emission

Excited State

Ground State

Absorption Emission

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic SpectroscopyAtomic Absorption and Atomic Emission

PrinciplesAtomic spectra are generatedby transitions of electronsfrom one discrete orbital toanother in an atom The difference in energybetween respective orbitalscorresponds to the energyof the electromagneticradiation in the UV-VisibleregionTwo processes namelyabsorption and emissionprovide analytical capability

Excited State

Ground State

AbsorptionEmission

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Technique

This technique was developed out of thephenomenon ndash observation of the spectrallines of solar radiationThe understanding of this observation is that(the spectral lines) the observed spectrum isdue to the absorption of light in the atomicvapor in the Sunrsquos atmosphere - Discovery inthe 1925sStrong absorption of optical radiation by atomsof an element could be induced if the samplewere excited by the atomic radiation of thatelement

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption hellip

Simple explanation

Induced radiation of the element excites thesample material causing excitement of theelectrons of the specific element from lower tohigher orbitals

Absorbs radiation from the sample

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

• Slide 1
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January 18 2006 IAP 2006 12091Session 3A P ILA

IntroductionAnalytical technique is a tool to determinebull abundances of elementsbull information about mineralsbull information about organics

May be categorized asbull inorganic and organicbull qualitative and quantitativebull spectroscopic and classical

January 18 2006 IAP 2006 12091Session 3A P ILA

Introduction hellipbull Qualitative means ndash identificationbull Quantitative means - determining theabundanceThe basic concept of quantitative analysisTake a material with known abundances calledthe standardUsing the known amount of abundance(s) in thestandard estimate the abundance(s) in theunknown called the sample maintaining all theconditions and parameters same for the sampleand the standard

January 18 2006 IAP 2006 12091Session 3A P ILA

Spectroscopic vs Classical Techniquesbull Spectroscopic analytical techniques utilizeelectromagnetic radiation interaction with thematerials for analysisbull Classical techniques utilize physical propertiescolor conductivity densityelectric charge massrefraction volume

January 18 2006 IAP 2006 12091Session 3A P ILA

Electromagnetic Radiation ndashSpectroscopic Techniques

Electromagnetic radiation consistsof two sinusoidal waveforms namely electric and magneticpropagated along the same axisin planes perpendicular to eachotherThe electromagnetic wave hastwo propertiesEnergy EWavelength λ (or frequency υ)E = hc λ = hυh is Planckrsquos constantc is velocity of lightLight is a well known example ofelectromagnetic radiation

The blue curve indicates the electric vector and orange curvethe magnetic vector component

Figure by MIT OCW

Figure 1 Components of electromagnetic radiation

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 2 Calibration Curve

Quantitative analysisinvolvesdetermination of acalibration curve bymeasuring theanalytical signal as afunction of knownconcentrations of thestandard(s) conductedin a range of values

Figure 2 Calibration curve for quantitative analysis

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 3Electromagnetic Spectrum and Spectroscopic

Techniques

Based on Figure 31 pp 78 A Handbook of Silicate Rock Analysis P J Potts

January 18 2006 IAP 2006 12091Session 3A P ILA

Spectroscopic Techniques hellip

bull The different energies of the photons in theelectromagnetic spectrum are representative ofdifferent types of interactions in the atoms andmolecules and are detected and measured bydifferent types of spectroscopic techniquesbull Microwave and infrared spectroscopy use theproperties of molecular rotations andvibrationsbull Ultra violet and visible light spectroscopy utilizeabsorption and emission of energies of outerelectron transitionsbull X-ray fluorescence ndash inner electronsbull Gamma rays ndash nuclear transitions

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4APictorial depiction of Atomic Nucleus ndash Electron

Orbitals

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4BAtomic Absorption and Emission

Excited State

Ground State

Absorption Emission

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic SpectroscopyAtomic Absorption and Atomic Emission

PrinciplesAtomic spectra are generatedby transitions of electronsfrom one discrete orbital toanother in an atom The difference in energybetween respective orbitalscorresponds to the energyof the electromagneticradiation in the UV-VisibleregionTwo processes namelyabsorption and emissionprovide analytical capability

Excited State

Ground State

AbsorptionEmission

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Technique

This technique was developed out of thephenomenon ndash observation of the spectrallines of solar radiationThe understanding of this observation is that(the spectral lines) the observed spectrum isdue to the absorption of light in the atomicvapor in the Sunrsquos atmosphere - Discovery inthe 1925sStrong absorption of optical radiation by atomsof an element could be induced if the samplewere excited by the atomic radiation of thatelement

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption hellip

Simple explanation

Induced radiation of the element excites thesample material causing excitement of theelectrons of the specific element from lower tohigher orbitals

Absorbs radiation from the sample

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Introduction hellipbull Qualitative means ndash identificationbull Quantitative means - determining theabundanceThe basic concept of quantitative analysisTake a material with known abundances calledthe standardUsing the known amount of abundance(s) in thestandard estimate the abundance(s) in theunknown called the sample maintaining all theconditions and parameters same for the sampleand the standard

January 18 2006 IAP 2006 12091Session 3A P ILA

Spectroscopic vs Classical Techniquesbull Spectroscopic analytical techniques utilizeelectromagnetic radiation interaction with thematerials for analysisbull Classical techniques utilize physical propertiescolor conductivity densityelectric charge massrefraction volume

January 18 2006 IAP 2006 12091Session 3A P ILA

Electromagnetic Radiation ndashSpectroscopic Techniques

Electromagnetic radiation consistsof two sinusoidal waveforms namely electric and magneticpropagated along the same axisin planes perpendicular to eachotherThe electromagnetic wave hastwo propertiesEnergy EWavelength λ (or frequency υ)E = hc λ = hυh is Planckrsquos constantc is velocity of lightLight is a well known example ofelectromagnetic radiation

The blue curve indicates the electric vector and orange curvethe magnetic vector component

Figure by MIT OCW

Figure 1 Components of electromagnetic radiation

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 2 Calibration Curve

Quantitative analysisinvolvesdetermination of acalibration curve bymeasuring theanalytical signal as afunction of knownconcentrations of thestandard(s) conductedin a range of values

Figure 2 Calibration curve for quantitative analysis

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 3Electromagnetic Spectrum and Spectroscopic

Techniques

Based on Figure 31 pp 78 A Handbook of Silicate Rock Analysis P J Potts

January 18 2006 IAP 2006 12091Session 3A P ILA

Spectroscopic Techniques hellip

bull The different energies of the photons in theelectromagnetic spectrum are representative ofdifferent types of interactions in the atoms andmolecules and are detected and measured bydifferent types of spectroscopic techniquesbull Microwave and infrared spectroscopy use theproperties of molecular rotations andvibrationsbull Ultra violet and visible light spectroscopy utilizeabsorption and emission of energies of outerelectron transitionsbull X-ray fluorescence ndash inner electronsbull Gamma rays ndash nuclear transitions

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4APictorial depiction of Atomic Nucleus ndash Electron

Orbitals

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4BAtomic Absorption and Emission

Excited State

Ground State

Absorption Emission

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic SpectroscopyAtomic Absorption and Atomic Emission

PrinciplesAtomic spectra are generatedby transitions of electronsfrom one discrete orbital toanother in an atom The difference in energybetween respective orbitalscorresponds to the energyof the electromagneticradiation in the UV-VisibleregionTwo processes namelyabsorption and emissionprovide analytical capability

Excited State

Ground State

AbsorptionEmission

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Technique

This technique was developed out of thephenomenon ndash observation of the spectrallines of solar radiationThe understanding of this observation is that(the spectral lines) the observed spectrum isdue to the absorption of light in the atomicvapor in the Sunrsquos atmosphere - Discovery inthe 1925sStrong absorption of optical radiation by atomsof an element could be induced if the samplewere excited by the atomic radiation of thatelement

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption hellip

Simple explanation

Induced radiation of the element excites thesample material causing excitement of theelectrons of the specific element from lower tohigher orbitals

Absorbs radiation from the sample

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Spectroscopic vs Classical Techniquesbull Spectroscopic analytical techniques utilizeelectromagnetic radiation interaction with thematerials for analysisbull Classical techniques utilize physical propertiescolor conductivity densityelectric charge massrefraction volume

January 18 2006 IAP 2006 12091Session 3A P ILA

Electromagnetic Radiation ndashSpectroscopic Techniques

Electromagnetic radiation consistsof two sinusoidal waveforms namely electric and magneticpropagated along the same axisin planes perpendicular to eachotherThe electromagnetic wave hastwo propertiesEnergy EWavelength λ (or frequency υ)E = hc λ = hυh is Planckrsquos constantc is velocity of lightLight is a well known example ofelectromagnetic radiation

The blue curve indicates the electric vector and orange curvethe magnetic vector component

Figure by MIT OCW

Figure 1 Components of electromagnetic radiation

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 2 Calibration Curve

Quantitative analysisinvolvesdetermination of acalibration curve bymeasuring theanalytical signal as afunction of knownconcentrations of thestandard(s) conductedin a range of values

Figure 2 Calibration curve for quantitative analysis

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 3Electromagnetic Spectrum and Spectroscopic

Techniques

Based on Figure 31 pp 78 A Handbook of Silicate Rock Analysis P J Potts

January 18 2006 IAP 2006 12091Session 3A P ILA

Spectroscopic Techniques hellip

bull The different energies of the photons in theelectromagnetic spectrum are representative ofdifferent types of interactions in the atoms andmolecules and are detected and measured bydifferent types of spectroscopic techniquesbull Microwave and infrared spectroscopy use theproperties of molecular rotations andvibrationsbull Ultra violet and visible light spectroscopy utilizeabsorption and emission of energies of outerelectron transitionsbull X-ray fluorescence ndash inner electronsbull Gamma rays ndash nuclear transitions

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4APictorial depiction of Atomic Nucleus ndash Electron

Orbitals

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4BAtomic Absorption and Emission

Excited State

Ground State

Absorption Emission

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic SpectroscopyAtomic Absorption and Atomic Emission

PrinciplesAtomic spectra are generatedby transitions of electronsfrom one discrete orbital toanother in an atom The difference in energybetween respective orbitalscorresponds to the energyof the electromagneticradiation in the UV-VisibleregionTwo processes namelyabsorption and emissionprovide analytical capability

Excited State

Ground State

AbsorptionEmission

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Technique

This technique was developed out of thephenomenon ndash observation of the spectrallines of solar radiationThe understanding of this observation is that(the spectral lines) the observed spectrum isdue to the absorption of light in the atomicvapor in the Sunrsquos atmosphere - Discovery inthe 1925sStrong absorption of optical radiation by atomsof an element could be induced if the samplewere excited by the atomic radiation of thatelement

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption hellip

Simple explanation

Induced radiation of the element excites thesample material causing excitement of theelectrons of the specific element from lower tohigher orbitals

Absorbs radiation from the sample

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Electromagnetic Radiation ndashSpectroscopic Techniques

Electromagnetic radiation consistsof two sinusoidal waveforms namely electric and magneticpropagated along the same axisin planes perpendicular to eachotherThe electromagnetic wave hastwo propertiesEnergy EWavelength λ (or frequency υ)E = hc λ = hυh is Planckrsquos constantc is velocity of lightLight is a well known example ofelectromagnetic radiation

The blue curve indicates the electric vector and orange curvethe magnetic vector component

Figure by MIT OCW

Figure 1 Components of electromagnetic radiation

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 2 Calibration Curve

Quantitative analysisinvolvesdetermination of acalibration curve bymeasuring theanalytical signal as afunction of knownconcentrations of thestandard(s) conductedin a range of values

Figure 2 Calibration curve for quantitative analysis

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 3Electromagnetic Spectrum and Spectroscopic

Techniques

Based on Figure 31 pp 78 A Handbook of Silicate Rock Analysis P J Potts

January 18 2006 IAP 2006 12091Session 3A P ILA

Spectroscopic Techniques hellip

bull The different energies of the photons in theelectromagnetic spectrum are representative ofdifferent types of interactions in the atoms andmolecules and are detected and measured bydifferent types of spectroscopic techniquesbull Microwave and infrared spectroscopy use theproperties of molecular rotations andvibrationsbull Ultra violet and visible light spectroscopy utilizeabsorption and emission of energies of outerelectron transitionsbull X-ray fluorescence ndash inner electronsbull Gamma rays ndash nuclear transitions

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4APictorial depiction of Atomic Nucleus ndash Electron

Orbitals

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4BAtomic Absorption and Emission

Excited State

Ground State

Absorption Emission

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic SpectroscopyAtomic Absorption and Atomic Emission

PrinciplesAtomic spectra are generatedby transitions of electronsfrom one discrete orbital toanother in an atom The difference in energybetween respective orbitalscorresponds to the energyof the electromagneticradiation in the UV-VisibleregionTwo processes namelyabsorption and emissionprovide analytical capability

Excited State

Ground State

AbsorptionEmission

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Technique

This technique was developed out of thephenomenon ndash observation of the spectrallines of solar radiationThe understanding of this observation is that(the spectral lines) the observed spectrum isdue to the absorption of light in the atomicvapor in the Sunrsquos atmosphere - Discovery inthe 1925sStrong absorption of optical radiation by atomsof an element could be induced if the samplewere excited by the atomic radiation of thatelement

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption hellip

Simple explanation

Induced radiation of the element excites thesample material causing excitement of theelectrons of the specific element from lower tohigher orbitals

Absorbs radiation from the sample

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 2 Calibration Curve

Quantitative analysisinvolvesdetermination of acalibration curve bymeasuring theanalytical signal as afunction of knownconcentrations of thestandard(s) conductedin a range of values

Figure 2 Calibration curve for quantitative analysis

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 3Electromagnetic Spectrum and Spectroscopic

Techniques

Based on Figure 31 pp 78 A Handbook of Silicate Rock Analysis P J Potts

January 18 2006 IAP 2006 12091Session 3A P ILA

Spectroscopic Techniques hellip

bull The different energies of the photons in theelectromagnetic spectrum are representative ofdifferent types of interactions in the atoms andmolecules and are detected and measured bydifferent types of spectroscopic techniquesbull Microwave and infrared spectroscopy use theproperties of molecular rotations andvibrationsbull Ultra violet and visible light spectroscopy utilizeabsorption and emission of energies of outerelectron transitionsbull X-ray fluorescence ndash inner electronsbull Gamma rays ndash nuclear transitions

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4APictorial depiction of Atomic Nucleus ndash Electron

Orbitals

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4BAtomic Absorption and Emission

Excited State

Ground State

Absorption Emission

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic SpectroscopyAtomic Absorption and Atomic Emission

PrinciplesAtomic spectra are generatedby transitions of electronsfrom one discrete orbital toanother in an atom The difference in energybetween respective orbitalscorresponds to the energyof the electromagneticradiation in the UV-VisibleregionTwo processes namelyabsorption and emissionprovide analytical capability

Excited State

Ground State

AbsorptionEmission

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Technique

This technique was developed out of thephenomenon ndash observation of the spectrallines of solar radiationThe understanding of this observation is that(the spectral lines) the observed spectrum isdue to the absorption of light in the atomicvapor in the Sunrsquos atmosphere - Discovery inthe 1925sStrong absorption of optical radiation by atomsof an element could be induced if the samplewere excited by the atomic radiation of thatelement

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption hellip

Simple explanation

Induced radiation of the element excites thesample material causing excitement of theelectrons of the specific element from lower tohigher orbitals

Absorbs radiation from the sample

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

• Slide 1
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January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 3Electromagnetic Spectrum and Spectroscopic

Techniques

Based on Figure 31 pp 78 A Handbook of Silicate Rock Analysis P J Potts

January 18 2006 IAP 2006 12091Session 3A P ILA

Spectroscopic Techniques hellip

bull The different energies of the photons in theelectromagnetic spectrum are representative ofdifferent types of interactions in the atoms andmolecules and are detected and measured bydifferent types of spectroscopic techniquesbull Microwave and infrared spectroscopy use theproperties of molecular rotations andvibrationsbull Ultra violet and visible light spectroscopy utilizeabsorption and emission of energies of outerelectron transitionsbull X-ray fluorescence ndash inner electronsbull Gamma rays ndash nuclear transitions

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4APictorial depiction of Atomic Nucleus ndash Electron

Orbitals

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4BAtomic Absorption and Emission

Excited State

Ground State

Absorption Emission

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic SpectroscopyAtomic Absorption and Atomic Emission

PrinciplesAtomic spectra are generatedby transitions of electronsfrom one discrete orbital toanother in an atom The difference in energybetween respective orbitalscorresponds to the energyof the electromagneticradiation in the UV-VisibleregionTwo processes namelyabsorption and emissionprovide analytical capability

Excited State

Ground State

AbsorptionEmission

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Technique

This technique was developed out of thephenomenon ndash observation of the spectrallines of solar radiationThe understanding of this observation is that(the spectral lines) the observed spectrum isdue to the absorption of light in the atomicvapor in the Sunrsquos atmosphere - Discovery inthe 1925sStrong absorption of optical radiation by atomsof an element could be induced if the samplewere excited by the atomic radiation of thatelement

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption hellip

Simple explanation

Induced radiation of the element excites thesample material causing excitement of theelectrons of the specific element from lower tohigher orbitals

Absorbs radiation from the sample

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Spectroscopic Techniques hellip

bull The different energies of the photons in theelectromagnetic spectrum are representative ofdifferent types of interactions in the atoms andmolecules and are detected and measured bydifferent types of spectroscopic techniquesbull Microwave and infrared spectroscopy use theproperties of molecular rotations andvibrationsbull Ultra violet and visible light spectroscopy utilizeabsorption and emission of energies of outerelectron transitionsbull X-ray fluorescence ndash inner electronsbull Gamma rays ndash nuclear transitions

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4APictorial depiction of Atomic Nucleus ndash Electron

Orbitals

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4BAtomic Absorption and Emission

Excited State

Ground State

Absorption Emission

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic SpectroscopyAtomic Absorption and Atomic Emission

PrinciplesAtomic spectra are generatedby transitions of electronsfrom one discrete orbital toanother in an atom The difference in energybetween respective orbitalscorresponds to the energyof the electromagneticradiation in the UV-VisibleregionTwo processes namelyabsorption and emissionprovide analytical capability

Excited State

Ground State

AbsorptionEmission

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Technique

This technique was developed out of thephenomenon ndash observation of the spectrallines of solar radiationThe understanding of this observation is that(the spectral lines) the observed spectrum isdue to the absorption of light in the atomicvapor in the Sunrsquos atmosphere - Discovery inthe 1925sStrong absorption of optical radiation by atomsof an element could be induced if the samplewere excited by the atomic radiation of thatelement

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption hellip

Simple explanation

Induced radiation of the element excites thesample material causing excitement of theelectrons of the specific element from lower tohigher orbitals

Absorbs radiation from the sample

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4APictorial depiction of Atomic Nucleus ndash Electron

Orbitals

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4BAtomic Absorption and Emission

Excited State

Ground State

Absorption Emission

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic SpectroscopyAtomic Absorption and Atomic Emission

PrinciplesAtomic spectra are generatedby transitions of electronsfrom one discrete orbital toanother in an atom The difference in energybetween respective orbitalscorresponds to the energyof the electromagneticradiation in the UV-VisibleregionTwo processes namelyabsorption and emissionprovide analytical capability

Excited State

Ground State

AbsorptionEmission

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Technique

This technique was developed out of thephenomenon ndash observation of the spectrallines of solar radiationThe understanding of this observation is that(the spectral lines) the observed spectrum isdue to the absorption of light in the atomicvapor in the Sunrsquos atmosphere - Discovery inthe 1925sStrong absorption of optical radiation by atomsof an element could be induced if the samplewere excited by the atomic radiation of thatelement

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption hellip

Simple explanation

Induced radiation of the element excites thesample material causing excitement of theelectrons of the specific element from lower tohigher orbitals

Absorbs radiation from the sample

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 4BAtomic Absorption and Emission

Excited State

Ground State

Absorption Emission

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic SpectroscopyAtomic Absorption and Atomic Emission

PrinciplesAtomic spectra are generatedby transitions of electronsfrom one discrete orbital toanother in an atom The difference in energybetween respective orbitalscorresponds to the energyof the electromagneticradiation in the UV-VisibleregionTwo processes namelyabsorption and emissionprovide analytical capability

Excited State

Ground State

AbsorptionEmission

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Technique

This technique was developed out of thephenomenon ndash observation of the spectrallines of solar radiationThe understanding of this observation is that(the spectral lines) the observed spectrum isdue to the absorption of light in the atomicvapor in the Sunrsquos atmosphere - Discovery inthe 1925sStrong absorption of optical radiation by atomsof an element could be induced if the samplewere excited by the atomic radiation of thatelement

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption hellip

Simple explanation

Induced radiation of the element excites thesample material causing excitement of theelectrons of the specific element from lower tohigher orbitals

Absorbs radiation from the sample

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic SpectroscopyAtomic Absorption and Atomic Emission

PrinciplesAtomic spectra are generatedby transitions of electronsfrom one discrete orbital toanother in an atom The difference in energybetween respective orbitalscorresponds to the energyof the electromagneticradiation in the UV-VisibleregionTwo processes namelyabsorption and emissionprovide analytical capability

Excited State

Ground State

AbsorptionEmission

K shell orbital (2 electrons)

L shell orbital (8 electrons)

Nucleus

M shell orbital (18 electrons)

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Technique

This technique was developed out of thephenomenon ndash observation of the spectrallines of solar radiationThe understanding of this observation is that(the spectral lines) the observed spectrum isdue to the absorption of light in the atomicvapor in the Sunrsquos atmosphere - Discovery inthe 1925sStrong absorption of optical radiation by atomsof an element could be induced if the samplewere excited by the atomic radiation of thatelement

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption hellip

Simple explanation

Induced radiation of the element excites thesample material causing excitement of theelectrons of the specific element from lower tohigher orbitals

Absorbs radiation from the sample

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Technique

This technique was developed out of thephenomenon ndash observation of the spectrallines of solar radiationThe understanding of this observation is that(the spectral lines) the observed spectrum isdue to the absorption of light in the atomicvapor in the Sunrsquos atmosphere - Discovery inthe 1925sStrong absorption of optical radiation by atomsof an element could be induced if the samplewere excited by the atomic radiation of thatelement

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption hellip

Simple explanation

Induced radiation of the element excites thesample material causing excitement of theelectrons of the specific element from lower tohigher orbitals

Absorbs radiation from the sample

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption hellip

Simple explanation

Induced radiation of the element excites thesample material causing excitement of theelectrons of the specific element from lower tohigher orbitals

Absorbs radiation from the sample

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectroscopy

Principle

The sample material is excited by electromagnetic radiationcausing the excitation of the electrons from lower orbital state tohigher The intensity of absorbed light is proportional to theconcentration of the element in the sample materialHence the intensity of the inducing incident light radiation must beexactly the same as the energy difference of the orbitalsHence the requirement for a hollow cathode lamp ndash that enables theatomized sample material to be excited with an atomic linespectrum of precise wavelengthFlame Atomic Absorption Spectroscopy (FAAS) andGraphite Furnace Atomic Absorption Spectroscopy (GFAAS)have similar measurement technique but differ in sample injectionand atomization

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometer

An atomic absorption spectrometer consists of

Atomic Light SourceHollow cathode tube orelectrodeless discharge lampNebulizer for making the solution into aersolsAtomizer for atomizing the aerosolsMonochromator To disperse incidentpolychromatic radiation into constituentwavelengthsPhotomultiplier detectorRead out system Computer and peripherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 5 Schematic ofGraphite Furnace Atomic Absorption Spectrometer

Sample solution

Hollow cathode lampPolarizer

Graphite Fumace

Monochromator

Detector

Computer and perlpherals

January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Flame Atomic Absorption Spectroscopy

The sample solution is sprayed into the flame by the nebulizerThe flame is made from the Air-Acetylene or Nitrous Oxide-Acetylene gas torch The hollow cathode lamp consists of thefilament of the element to be analyzed and is filled with argon orneon gas

High voltage is applied to the lamp to generate the characteristicradiation which is isolated from the radiation from the flame by achopper

The detector consists of a photomultiplier tube which convertsthe incident EM radiation energy into an electrical signal

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 6 Schematic of Flame Atomic Absorption Spectrometer

SampleSolution

Hollow CathodeLamp

Chopper

Flame

Nebulizer

Computer and Peripherals

Detector

Monochromator

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Absorption Spectrometry

Eg Absorption LinesElement Wavelength nmAs 228812Cu 324754Iron 271903Iron 279470Iron 352414

January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Atomic Emission Spectroscopy

Principles

Atomic emission is induced whensome external source of energy suchas an argon plasma is utilized toprovoke the electron excitementtransitions When the excited electronsde-excite to the ground or lower stateorbitals the released energy is theintensity of the emission radiation

Other sources Arc-Spark

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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• Slide 64

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled PlasmaAtomic Emission Spectroscopy

Principle

The sample aerosol is lsquoheatedrsquo in a plasma The plasmais an ionized argon gas at high temperatures (6000K-10000K)

The plasma at these high temperatures excites theatoms of the sample aerosol and there by emittingEM radiation of characteristic wavelengths ofdifferent elements

This is thus a multi-element analytical technique

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

• Slide 1
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January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 7 Schematic ofInductively Coupled Plasma Atomic Emission Spectrometer

SampleSolution

Nebulizer

ICP Torch

RFGenerator

Argon

SprayChamber

Computer and Peripherals

Lens Polychromator

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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• Slide 64

January 18 2006 IAP 2006 12091Session 3A P ILA

ICPAES

Eg Emission linesElement wavelength nmAs 193696Cu 324724Iron 259940

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of liquids byInductively Coupled Plasma Mass (ICPMS)

Spectroscopy

ICPMS technique is useful for multi-element analysisof geological environmental and medical samplematerials

ICPMS provides information about the abundancesas well as isotopic ratios of the nuclides

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

• Slide 1
• Slide 2
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• Slide 60
• Slide 61
• Slide 62
• Slide 63
• Slide 64

January 18 2006 IAP 2006 12091Session 3A P ILA

Inductively Coupled Plasma Mass Spectrometer

Principle

The ICPMS technique consists of a hightemperature plasma into which the sampleaerosol is injected and positively charged ionsare generated by the interaction

A mass spectrometer quantifies the ionizationbased on the mass to charge ratio

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 8Schematic of Inductively Coupled Plasma Mass Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

• Slide 1
• Slide 2
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• Slide 61
• Slide 62
• Slide 63
• Slide 64

January 18 2006 IAP 2006 12091Session 3A P ILA

Analysis of Solids byNeutron Activation Analysis (NAA) and

Gamma Spectroscopy

PrincipleNeutron Activation Analysis is a nuclearanalytical technique that involves irradiatinga sample with neutrons The stableisotopes of different elements in the samplebecome radioactive The radioactivity ofdifferent radionuclides can be detected andquantified by gamma spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

• Slide 1
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• Slide 64

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

A stable isotope when bombarded with neutronsabsorbs a neutron and by the most common type ofnuclear reaction namely (n gamma) reaction getstransformed into higher mass unstable nucleus

When the unstable nucleus de-excites by promptgamma rays and gets transformed into a radioactivenucleus (with next higher neutron number) Thisradioactive nucleus decays mainly by beta rays and(or) characteristic gamma-rays

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
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• Slide 63
• Slide 64

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis hellip

Nuclear ReactionNuclear reaction occurs when target nuclei are bombarded with nuclearparticles depicted pictorially

Target X is bombarded by particle ldquoardquoY is the product nuclei with resulting particle ldquobrdquo Q is the energy of the nuclear reaction which is the difference between themasses of the reactants and the products

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysishellip

1)Neutron captureThe target nucleus absorbs (captures) aneutron resulting in a product isotope themass number of which is incremented byone If the product nucleus is unstable itusually de-excites by emission of gammarays andor β

Ex

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

An irradiated material is radioactiveemitting radiations ndash α β γ helliphelliphellip

For Neutron Activation Analysis ndash usuallygamma radiation is selected

Gamma spectrometer is the detectionsystem that measures gamma ray intensity

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrometer

Gamma spectrometer system formeasuring the gamma-ray activity of anirradiated material consists typically of1) Detector2) Amplifier3) Multi Channel Analyzer4) Computer amp peripheralsThis is shown pictorially

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 9 Schematic of Gamma Spectrometer

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The energy of nuclear radiation is convertedinto an electrical signal by a device that is thenuclear radiation detectorThe three major categories of gammadetectors used in Neutron Activation Analysisare1)Scintillators NaI(Tl) CsF ZnS(Ag)2)Semiconductors Si Ge CdTe GaAs3)Gas Filled He Air H2 N2

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorhellip

The nuclear radiations emanating from theirradiated material will cause ionization in thedetector medium by means of charged particleproducts of their interactions

The scintillators and the semiconductors haveenergy discrimination capacity better than thegas filled detectors

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma detectorshellip

The nuclear radiations incident on the detectorcrystal initiate ionizations by creation of electrons(negative charge) and holes (positive charge)

An electric field is created by applying high voltageto the electrodes mounted on opposite sides ofthe detector crystal The charge carriers getattracted to the electrodes of opposite polaritybecause of the electric field The charge collectedat the electrodes is proportional to the energy lostby the incident radiation

Chapter IV Instrumentation in neutron activation analysis by P Jagam and G K Muecke p 77 Figure 43Mineralogical Association of Canada Short Course in Neutron Activation Analysis in the Geosciences Halifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 10Schematic diagram of conduction and forbidden bands

of a semiconductor detector crystal

Conductionband

Forbidden energyband

Valenceband

KEY- Shading indicates valence band fully occupied by electrons Arrows indicate direction of ionizationof electrons to or from impurity atoms

Schematic behaviour of a semiconductor crystalA Perfect (intrinsic) semi-conductor at 0 K the valence band is fully occupied by electrons and the conduction band is empty in thisstate the semiconductor cannot conductB Semiconductor at 77 K vast reduction in thermal ionization to conduction bandC Semiconductor at room temperature significant thermal excitation of electrons from valence to conduction band in this state thesemiconductor will conductD Effect of donor atom impurities in n-type semiconductor materialE Effect of acceptor atom impurities in p-type semiconductor material

Reference A Handbook of Silicate Rock Analysis by P J Potts Blackie Chapman and Hall New York page 406 Figure 127

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matter

Photoelectric effect is theinteraction between the incidentgamma-ray and orbital electron of theatom of the detector crystal Theenergy of the gamma-ray iscompletely transferred to the electronThe electron overcomes theionization potential by utilizing part ofthe transferred energy the remainderbecomes the kinetic energy of theelectron Photoelectric interactionpredominantly takes place with orbitalshells close to the nucleus (K-shell)The vacancy created by the ionizedelectron gets filled by an electronfalling from the next higher shellsimultaneously emitting thecharacteristic K X rays of Ge Thuscharacteristic X rays of the detectormaterial are emitted whenphotoelectric interaction takes place

Figure 11Schematic depiction ofPhoto Electric Effect

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation with matterhellip

Compton scattering is the interactionbetween the incident gamma ray andan outer orbital electron in which onlypart of the gamma energy istransferred to the electron and the theremainder is reirradiated as a lowerenergy gamma ray (scatteredinelastically) preserving the totalenergy and momentum In a head-oncollison maximum transfer of energyoccurs following which the secondarygamma ray is emitted at 180 to thefirst The secondary gamma photoncan itself interact by further comptonor photoelectric interactionsHowever there is a probability thatthis gamma will itself escape from thedetector Compton scattering in thedetector is the main cause of the highbackground contnuum below theenergies of the principal gammaphoto peaks recorded on Gedetectors

Figure 12Schematic depiction of

Compton Scattering

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Pair production interaction becomessignificant when incident gammaray energies exceed 1022 MeVThe interaction of the incidentgamma-ray in the strongelectromagnetic field surroundingthe nucleus results in completetransmutation of gamma photonenergy into an electron ndash positronpair The particles which arevery short lived lose their kineticenergy very quickly by furthercollison with the atoms of thedetector and then spontaneouslyannihilate to generate two 511keV gamma ndashrays emitted at 180degrees to one another

Figure 13Schematic diagram of

Pair Production

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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• Slide 2
• Slide 3
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January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiation withmatterhellip

Bremsstrahlung

Bremsstrahlung continuumradiation is also created in thedetector by the deceleration ofenergetic electrons within theelectrostatic fields surroundingthe nucleusBremsstrahlung radiation canrandomly contribute to thecontinuum spectrum

Figure 14Schematic diagram of

Bremsstrahlung interaction

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 15Energy Calibration of a Gamma Spectrometer using

Standard Calibration Sources

Source Gamma-ray Channel Energy Number keV57Co 1230 366137Cs 66164 198560Co 117321 3521 133248 3996

January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Gamma Spectrum - MultielementReferenceMultielement analysis of food spices by instrumental neutron activation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980) 205-210

Figure 16 Multi-element gamma-ray spectrum of a food material

January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Interaction of gamma radiationwith matter

Gamma radiation interacts with matter causingionization in matter by three principalprocesses

1)Photoelectric effect2)Compton scattering3)Pair production

Reference Chapter 126 Interaction of gamma-radiation with Ge detectors A Handbook of Silicate Rock Analysis by P J PottsBlackie Chapman and Hall New York page 412 Figure 1217

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
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January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation

A = number of decays per second (Activity) dpsN = number of atoms of the target isotope= m x q x 6023 x 1023Wm = mass of the element in the irradiated sample gθ = isotopic abundancew = Atomic weight of the elementλ = decay constant = 0693t12t12 = Half-life of the isotopeφ = neutron flux ncm-2 sec-1σ = activation cross-section 10-24 cm2tirr = irradiation time sec

January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Activity Equation hellip

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

• Slide 1
• Slide 2
• Slide 3
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• Slide 64

January 18 2006 IAP 2006 12091Session 3A P ILA

Neutron Activation Analysis bycomparator method

AStandard = Activity of an isotope ofan element in the known (Standard) isproportional to the amount present

ASample = Activity of the isotope ofthe same element in the unknown(Sample)

AmountStandard AmountSample= AStandard ASample

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
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• Slide 59
• Slide 60
• Slide 61
• Slide 62
• Slide 63
• Slide 64

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 17 Trace element abundance determination by Neutron Activation Analysisof different elements

Based on Neutron Activation Analysis Modern Analytical Geochemistry pp 116-135

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion

Neutron Activation Analysis1 Nuclear technique that measures the intensity ofgamma rays of characteristic energy using gammaspectroscopy2 Multielement Analysis3 Rapid analyses of multiple samples4 Sample size can be variable (typically 1 mg to 1 gm)

January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Conclusion hellip

5 Nondestructive - that is valuable and safe samples are not destroyed6 No Chemical processing therefore samples are not contaminatedduring sample preparation no uncertainty about total dissolution ofsample no need for dilutions of solutions making the techniquevaluable and safe Samples are not destroyed7 No need for repeated blank measurements because no memory effects8 Gamma ray spectroscopy is largely free from matrix interferences9 Depending on the sample matrix elemental concentrations can bedetermined at parts per million (ppm) parts per billion (ppb) and partsper trillion (ppt) level10Versatile (in use for more than half a century) well established andreliable

January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Table 1 Summary of features of Atomic and Nuclear analyticalTechniques

Based on Table VII pp 716 Essentials of Medical Geology

January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Electron Probe Microanalysis

Electron probe microanalysis technique is useful toanalyze the composition of a selected surface area ofdiameter size of few microns (micron = 0001 meter =01 cm) of the sampleFor example in geological materials ndash can determinecomposition of individual mineralsvariation of concentration within a single grainFor this type of analysis ndash the samples are to bepolished thin sections mountedin a resin block orglass slide backing

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 18 Schematic of Electron Microprobe

January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Figure 19Wavelength Dispersive XRF (WDXRF)

Energy Dispersive XRF (EDXRF) hellip

PrinciplesIn a stable atom electronsoccupy in discrete energyorbitals the notation ofthese orbitals indecreasing binding energylevel is K L M hellipThe sample is excited bymeans electromagneticradiation generated byradioisotopes X-ray tubescharged particles(electrons protons andalpha particles)WDXRF use X-ray tubesEDXRF uses both X-raytube and radio-isotopes

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF) hellip

When the energy of the excitingsource radiation is higher than thebinding energy of an electron in theinner orbital the electron getsejected and the atom becomesionized But the vacancy created bythe ejected electrons filled by ahigher energy electron in the outerorbital As a result of this event aphotoelectron will be emitted withcharacteristic wavelength or energy(difference between the energies ofthe two levels) This emitted photonsometimes may be reabsorbedimmediately (causing no emission)Fluorescence yield is the probabilityof emission of characteristic K LM hellipX-ray lines It increases withincreasing atomic number anddecreases with KgtLgtM hellip

Figure by MIT OCW

January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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• Slide 2
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January 18 2006 IAP 2006 12091Session 3A P ILA

Wavelength Dispersive XRF (WDXRF)Energy Dispersive XRF (EDXRF)

Dispersive means separation and measurement

WDXRF ndash Separation is done by collimators anddiffraction crystals Measurement is done bydetecting the characteristic wavelengths byscintillation detectors and proportional countersproviding a pulse height distributed spectrum

EDXRF ndash the wavelength dispersive crystal anddetector system is replaced by solid state energydispersive system consisting of Si(Li) detectorcoupled to a Multichannel analyzer system

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

• Slide 1
• Slide 2
• Slide 3
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• Slide 64

January 18 2006 IAP 2006 12091Session 3A P ILA

Review Quiz

1 Explain the dose response curve with reference toessentiality and non-essentiality and health effects

2 List 5 essential elements and briefly describe theirhealth effects due to deficiency and toxicity

3 List 5 toxic elements and their effects on health

4 List the components and brief description of any oneanalytical technique

5 In a fictional town called Cleanland the town peopleare concerned about a piece of land they want todesignate for vegetable gardening They come to youfor consultation ndash what will you advise Explain

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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• Slide 2
• Slide 3
• Slide 4
• Slide 5
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• Slide 60
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• Slide 63
• Slide 64

January 18 2006 IAP 2006 12091Session 3A P ILA

Summary

I gave the overview of analytical techniquesAtomic Absorption and EmissionInductively Coupled Plasma Mass SpectrometryInstrumental Neutron Activation AnalysisElectron Microprobe - Wavelength and EnergyDispersive X-ray Spectroscopy

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
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• Slide 64

January 18 2006 IAP 2006 12091Session 3A P ILA

Internet Keywords

1048710 Atomic absorption atomic emissionwavelength dispersive X-rayspectroscopy energy dispersive X-rayspectroscopy1048710 Neutron activation analysis1048710 Gamma spectrometer1048710 Interaction of gamma rays with matter1048710 Electron probe

January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

• Slide 1
• Slide 2
• Slide 3
• Slide 4
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January 18 2006 IAP 2006 12091Session 3A P ILA

References

Radiation detection and measurementsG F KnollNew York John Wiley amp Sons 1979ISBN 047149545X

Gamma and X-ray spectrometry with semiconductor detectorsK Debertin and R G HelmerNew York North Holland 1988ISBN 0444871071

Chapter IV Instrumentation in neutron activation analysisP Jagam and G K Muecke pages 73-108Mineralogical Association of CanadaShort Course in Neutron Activation Analysis in the GeosciencesHalifax May 1980 Ed G K Muecke

January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

References

A handbook of silicate rock analysisP J PottsNew York Blackie Chapman and Hall 1987ISBN 0-412-00881-5 (USA)

Principles of Instrumental AnalysisD A Skoog and D M WestHolt-Saunders Japan Tokyo 1980

Multielement analysis of food spices by instrumental neutronactivation analysisP Ila and P JagamJournal of Radioanalytical and Nuclear Chemistry 57 (1980)205-210

January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

Ewings analytical instrumentation handbook 3rd editionEditor Jack GazesNew York Marcel Dekker c2005

Practical inductively coupled plasma spectroscopyJ R DeanHoboken NJ Wiley 2005

Spectrochemical analysis by atomic absorption and emissionLHJ Lajunen and P Peramaki 2nd edCambridge Royal Society of Chemistry c2004

References

January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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January 18 2006 IAP 2006 12091Session 3A P ILA

References

The atomic fingerprint neutron activation analysisB Keisch BernardHonolulu Hawaii University Press of the Pacific c2003

Analytical atomic spectrometry with flames and plasmasJ A C BroekaertWeinheim Wiley-VCH Chichester John Wiley[distributor] 2005

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