molecular mass spectrometry. mass spectroscopy (ms) the elemental composition of matter of samples ...
Post on 21-Dec-2015
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Molecular Mass Molecular Mass SpectrometrySpectrometry
Mass Spectroscopy (MS)Mass Spectroscopy (MS)
The elemental composition of matter of samples
The structure of inorganic, organic and biological molecules
The quantitative and qualitative composition of complex mixture
Isotopic ratios of atoms in samples
MS - ComponentsMS - Components
Components of Mass Spectrometer
GC/MS System ComponentsGC/MS System Components
MS - IonizationMS - Ionization
Gas phase ionization (103 D):
Electron Impact (EI) – Energetic electron beam
Chemical Ionization (CI) – Reagent gaseous ions
Field Ionization (FI) – high potential electrode
MS - IonizationMS - Ionization Desorption Ionization (105 D):
Field Desorption (FD) – High-potential Electrode
Electrospray Ionization (ESI) – High Electric Field (20 kV)
Matrix – Assisted Desorption/Ionization (MALDI)
Plasma desorption (PD) – Fission fragments from 252Cf
Thermospray ionization (TS) – High temperature
MS - IonizationMS - Ionization
Hard source – enough energy to rupture bonds and producing fragments (EI)
Soft source – provides always molecular weight of the molecule (CI; ESI,
MALDI)
MS – Electron-Impact Ionization
MS – Ionization ChamberMS – Ionization Chamber
MS – Ring Component SpectrumMS – Ring Component Spectrum
MS - SpectraMS - Spectra
CH2Cl2
MW=84
1-PentanolMW=88
MS - ChromatogramMS - Chromatogram
MS – Isotopes AbundanceMS – Isotopes AbundanceMost Other Percentage (%)
H1 H2 0.015
C12 C13 1.08
N14 N15 0.37
S32 S33 0.8
S34 4.4
Cl35 Cl37 32.5
Br79 Br81 98.0
Si28 Si29 5.1
Si30 3.4
MS – Effect of Ionization Mode on SpectraMS – Effect of Ionization Mode on SpectraEI
Field Ionization
Field Desorption
Glutamic AcidHOOC-CHNH2 -CH2 – CH2 - COOH
MS – Ionization Mode and SpectraMS – Ionization Mode and Spectra
Electron- Impact
Chemical Ionization
1- DecanolMW = 158
MS – Chemical IonizationMS – Chemical Ionization
• Most often use reagent is CH4:
• Electrons will form several ions: CH4+; CH3
+; CH2
+
• Reactions (MH – sample molecule):
CH4+ + CH4 CH5
+ + CH3
CH5+ + MH MH2
+ + CH4 (M + 1)
CH3+ + CH4 C2H5
+ + H2
C2H5+ + MH M+ + C2H6 (M – 1)
(M + 29)
GC/MS – Jet SeparatorGC/MS – Jet Separator
GC/LC/MSGC/LC/MSSample Sample TransferTransfer
MS – Direct Sample IntroductionMS – Direct Sample Introduction
Direct Sample Probe
External Sample Introduction System
MS – Mass AnalyzerMS – Mass Analyzer• Resolution:
R = m/m
Where: m – mass of the first peak
m – difference between two adjacent peaks
Commercial MS have resolution 500 to 500,000
m = m/R
MS Analyzer – Magnetic Sector
MS – Electromagnetic AnalyzerMS – Electromagnetic Analyzer
Quadrupole MS Analyzer
MS – Quadrupole FilterMS – Quadrupole Filter
MS - Ion Trap Analyzer
MS – Time of Flight Analyser
MS – Reflectron Time of Flight Analyzer
MS – Fourier Transform AnalyzerMS – Fourier Transform Analyzer
Ion Cyclotron Resonance
Magnetic Field
GCMS - InstrumentationGCMS - Instrumentation
MS - InstrumentationMS - Instrumentation
LCMS – Electrospray Ionization (ESI)LCMS – Electrospray Ionization (ESI)
MS – Capillary ElectrophoresisMS – Capillary Electrophoresis
MS – Supercritical ChromatographyMS – Supercritical Chromatography
MS – Ion DetectorMS – Ion Detector
MS/MSMS/MS
MS/MS Instrumentation MS/MS Instrumentation
MS - CostMS - Cost
Mass SpectrumMass Spectrum
5-Ethyl-5n-hexyl barbituric acid
MW 240
MS - ChromatogramMS - Chromatogram
MS - QuantitativeMS - Quantitative
SIM – single ion monitoring
Spectra mode
Precision – 2% to 10%
MS – Spectra InterpretationMS – Spectra Interpretation
Base peaks and Relative Ion Intensities: Determine molecular ion mass. CI if needed.
Elemental composition from isotopic abundance: Look for A+2 pattern elements (Cl, Br, S, Si, O) Check A+1 ratios for absence/presence of S and Si Use the nitrogen rule to determine number of N’s (If
MW is even N=0 or even number. If MW is odd = odd number of nitrogen atoms
Estimate number of H, F, I, and P from isotopic ratios and MW balance (P is multivalent; F=19; I=127 mass units)
Check allowance for rings and double bonds. Number of double bonds or rings = x – 1/2y +1/2 z +1 (x=C, Si; y=H, F, Br, Cl; z=N, P, O, S)
MS – Spectra InterpretationMS – Spectra Interpretation
Use molecular ion fragmentation mechanism:Check fragment masses differences for expected
losses (Cl = 35; Br=79; Me=15; Et=29 etc…) Look for expected substructures Look for stable neutral loss (CH2 == CHR)
Look for products of known rearrangements
Postulate structures:Search library data base Run hit compound on the same instrument to
confirm
Use MS/MS if further confirmation is needed
MS - ApplicationsMS - Applications