elemental analysis of plants (icp and ea)

Vasiliy V. Rosen, M.Sc., ZBM Analytical Laboratory

www.rosen.r8.org

2012

Essential

Toxic

Major Micronutrients

Carbon (C)

Oxygen (O)

Hydrogen (H)

Nitrogen (N)

Phosphorus (P)

Potassium (K)

Sodium (Na)

Silica (Si)

Calcium (Ca)

Magnesium (Mg)

Sulfur (S)

Boron (B),

Chlorine (Cl)

Copper (Cu)

Iron (Fe)

Manganese (Mn)

Molybdenum (Mo)

Zinc (Zn)

Nickel (Ni)

Cobalt (Co)

Chromium (Cr)

Selenium (Se)

Vanadium (V)

Silver (Ag)

Aluminium (Al)

Arsenic (As)

Barium (Ba)

Berillium (Be)

Cadmium (Cd)

Mercury (Hg)

Lead (Pb)

Lithium (Li)

And all

micronutrients at

critical

concentration

The role of chemical elements in plants

(adopted from Munson R., 1997, and Macnicol R., 1984)

EA

ICP

EA – ELEMENTAL ANALYSIS OF C, H, N, S AND O

Sample state: dried, ground with a mill, 0.5-0.5 mm; or liquid

Sample weight: 2 – 3 mg

Supply: gases (He and O2 extra-pure)

EA – ELEMENTAL ANALYSIS OF C, H, N, S AND O

Sample combustion at 1020º – 1800º C

Oxidation by pure O2 to CO2, H2O, SO2, NOx

Reduction: Copper wires remove O2 and reduces NOx

to N2, SO3 to SO2

Chromatographic separation of N2, CO2, H2O and SO2

He

Catalyst - CuO

Catalyst - Cu

ATOMIC SPECTROSCOPY

After Boss. C.B. and Freden K.J. Concepts, Instrumentation and Techniques in

Inductively Coupled Plasma Optical Emission Spectrometry. 1997

E – energy difference between two levels;

h – Plank’s constant, 6.626068 × 10-34 m2kg/s;

c – speed of light, 299 792 458 m/s;

λ – wavelenght, nm

Ion Emission

Atom Emission

ICP-AES

Inductively Coupled Plasma

Atomic Emission Spectrometry

ATOMIC EMISSION SPECTROSCOPY

ICP-AES

Basics

Atomic emission spectroscopy measures the intensity of

light emitted by atoms or ions of the elements of interest at

specific wavelengths;

Inductively Coupled Plasma spectrometers use emission

spectroscopy to detect and quantify elements in a sample;

ICP-AES uses the argon plasma (6000º-10000º C) for

atomization and excitation of the sample atoms;

ICP-AES determines approximately all of the elements

except gases and some non-metals (C, N, F, O, H).

Schematic diagram of the processes in the ICP

After Spectro Gmbh, Germany

Flame (or Plasma) causes the

solvent to evaporate, leaving dry

aerosol particles, then volatilizes the

particles, producing atomic,

molecular and ionic species

ICP-AES SPECTROMETER ARCOS

ICP SPECTROMETER

Main Systems

ICP-AES: SAMPLE INTRODUCTION SYSTEM

Nebulizer (cross-flow)

Spray Chamber

Argon Supply

To Waste

Torch with Plasma

Sample

Solution

Entrance

After Manning T.J. and Grow W.P.,

1997

Inductively Coupled Plasma Source

A plasma is a hot, partially ionized

gas. It contains relatively high

concentrations of ions and electrons.

Argon ions, once formed in a plasma, are

capable of absorbing sufficient power from

an external source to maintain the

temperature at a level at which further

ionization sustains the plasma indefinitely.

The plasma temperature is about 10 000 K.

ICP-AES: PLASMA

Inductively Coupled Plasma Source

ICP-AES: PLASMA

After Spectro Gmbh, Germany

ICP-AES: RADIAL (SOP) AND AXIAL (EOP)

ICP-AES: RADIAL (SOP) AND AXIAL (EOP)

SOP: Side-on-Plasma EOP: End-on-Plasma

more suitable for hard matrices (concentrated samples);

alkali metals (Na, K, Li) calibration is more linear;

less spectral interferences;

lower sensitivity (Limit-of-Detection is higher);

more suitable for light matrices;

alkali metals (Na, K, Li) calibration is less linear;

more spectral interferences;

higher sensitivity (Limit-of-Detection is lower);

ICP-AES: OPTICS

After Spectro Gmbh, Germany; Boss. C.B. and Freden K.J. Concepts,

Instrumentation and Techniques in ICP-OES. 1997

ICP-AES: CALIBRATION CURVE

ICP-AES: SPECTRAL INTERFERENCES

Sulfur in plant sample Boron in plant sample

Sulfur in standard

(10 mg/L)

Boron in plant sample

Boron in standard

(1 mg/L)

Sulfur spectral interference on Boron line 182.6 nm

ICP-AES: SAMPLE PREPARATION

Most samples have to be prepared for analysis by ICP. Solid samples are solubilized.

Organic matter is "mineralized" i.e. converted to inorganic compounds.

Hot Plate

Microwave-assisted Digestion

Digestion Block

ICP-AES AND EA: APPLICATION

Environmental Analysis: trace metals and other elements in waters, soils, plants,

composts and sludges;

Clinical Analysis: metals in biological fluids (blood, urine);

Pharmaceuticals: traces of catalysts used; traces of poison metals (Cd, Pb etc);

Industry: trace metal analysis in raw materials; noble metals determination.

Forensic science: gunshot powder residue analysis, toxicological examination

( e.g., thallium (Tl) determination)