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GC-MS Gas Chromatography-Mass Spectrometry

GC-MS Gas Chromatography-Mass Spectrometry. Gas Chromatography-Mass Spectrometry. An Hybrid technique which couples the powerful separation potential of gas chromatography with the specific characterization ability of mass spectroscopy. Development of GC (1941) by Martin and Synge.

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GC-MS Gas Chromatography-Mass Spectrometry

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  1. GC-MSGas Chromatography-Mass Spectrometry

  2. Gas Chromatography-Mass Spectrometry An Hybrid technique which couples the powerful separation potential of gas chromatography with the specific characterization ability of mass spectroscopy. Development of GC (1941) by Martin and Synge

  3. What is Gas Chromatography? • The father of modern gas chromatography is Nobel Prize winner John Porter Martin, who also developed the first liquid-gas chromatograph. (1950)

  4. Chromatography

  5. Separation of molecules by distribution between a stationary phase and a mobile phase. • A stationary phase(absorbent) phase the material on which the separation takes place. can be solid, gel, or liquid. Also called matrix, resin, or beads. • The mobile phaseis the solvent transports the sample and it is usually a liquid, but may also be a gas. Also called eluting buffer • The compounds to be separated are considered solutes

  6. GC Step by Step • Carrier Gas • Injector • Column • Capillary • Stationary Phase • Detectors • Mass Spectrometer

  7. Depending on its nature 1.Packed column:columns are available in a packed manner 2.Open tubular or Capillary column or Golay column • Long capillary tubing 30-90 M in length • Uniform & narrow d.m of 0.025 - 0.075 cm • Made up of stainless steel & form of a coil • Disadvantage: more sample cannot loaded

  8. 3.SCOT columns (Support coated open tubular column • Improved version of Golay / Capillary columns, have small sample capacity • Made by depositing a micron size porous layer of supporting material on the inner wall of the capillary column • Then coated with a thin film of liquid phase

  9. Column Types Capillary Columns Length: 10m to 100m Diameter: 180um, 250um, 320um & 530um I.d Packed Columns Length: <2m Diameter: 1/8” & ¼” OD

  10. Columns • Packed • Capillary Cross section

  11. Phases

  12. Broadening can be minimized with: 1- decreasing particle size 2- decreasing column diameter

  13. What Does GC/MS Data Look Like?Reviewing of Mass Spectra 6.77 min. * * Abundance (Signal) Retention Time ------> m/z 78 mass/charge ------> 1,1-dichloropropene/carbon tetrachloride

  14. Example Chromatogram (Capillary) Detector Response Inject Point Time 

  15. DETECTORS • Heart of the apparatus The requirements of an ideal detector are- • Applicability to wide range of samples • Rapidity • High sensitivity • Linearity • Response should be unaffected by temperature, flow rate… • Non destructive • Simple & inexpensive

  16. Flame Ionization Detector

  17. Thermal Conductivity Detector

  18. Electron Capture Detector

  19. Application of GC

  20. Analysis of Halogenated Pesticides 4 10 7 11 6 8 12 13 9 14 1 5 15 17 18 3 16 2 2ppb in Water

  21. Schematic of a Gas Chromatography-Mass Spectrometry (GC-MS) Instrument

  22. Ionization techniques - EI (electron impact) - CI (chemical ionization) - FAB (fast atom bombardment) - ESI (electrospray ionization) - MALDI (matrix assisted laser desorption ionization) - APCI (atmospheric pressure chemical ionization)

  23. Electron Impact Ioniser • In an electron-impact mass spectrometer (EI-MS), a molecule is vaporized and ionized by bombardment with a beam of high-energy electrons. • The energy of the electrons is ~ 1600 kcal (or 70eV). • The electron beam ionizes the molecule by causing it to eject an electron.

  24. Quadrupole Mass Ion Filter Quadrupoles are four precisely parallel rods with a direct current (DC) voltage and a superimposed radio-frequency (RF) potential. The field on the quadrupoles determines which ions are allowed to reach the detector. Quadrupoles thus function as a mass filter.

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