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Gas Chromatography

Gas Chromatography Basics. Gas Liquid Chromatography (GLC)Gas Solid Chromatography (GSC)Mobile phase does not interact with analyteSeparation occurs by interaction of analyte differentially w/liquid stationary phase and temperatureGC preferred method, only applicable to volatile substancesderivitiazation.

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Gas Chromatography

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    1. Gas Chromatography

    2. Gas Chromatography Basics Gas Liquid Chromatography (GLC) Gas Solid Chromatography (GSC) Mobile phase does not interact with analyte Separation occurs by interaction of analyte differentially w/liquid stationary phase and temperature GC preferred method, only applicable to volatile substances derivitiazation

    3. Carrier Gas Supply Must be at a constant flow rate so that retention times & retention volumes may be equated Choice of detector will often Dictate the gases that are used, need to be inert Ex. FID used H2, air, and He

    4. Injection Port Heated so sample virtually instantly turns into a vapor as sample plug goes onto column Septum Split/ Splitless 1uL injected into instrument in split mode only 1-2% actually is injected on the column Also talk about sample focusing play focus.qt1uL injected into instrument in split mode only 1-2% actually is injected on the column Also talk about sample focusing play focus.qt

    5. Flow rate Measurement Why is a known flow rate critical?

    6. GC Columns Capillary: - have i.d. <1mm - have wide unrestricted flow through center & inner surface is coated with liquid stationary phase Variety of functional groups have been blended into polysiloxane chain to provide different polarity & selectivity

    7. Capillary columns Advantages Disadvantages

    10. Polydimethyl siloxane 5% phenyl methyldimethyl siloxane 50% phenyl methyldimethyl siloxane D. 50% poly(trifluoropropyl-dimethyl siloxane E. polyethylene glycol F. 50% polycyanopropyl-dimethyl siloxane Polydimethyl siloxane 5% phenyl methyldimethyl siloxane 50% phenyl methyldimethyl siloxane D. 50% poly(trifluoropropyl-dimethyl siloxane E. polyethylene glycol F. 50% polycyanopropyl-dimethyl siloxane

    11. Temperature

    12. Chromatography Catalog Exercise Determine the best type of column to achieve separation for drugs of abuse. Draw the chemical structures of the stationary phase as best you can. Indicate what chromatographic conditions you would do your separation under. Why do you think the catalog recommended the conditions they did? Compare with someone else who used a different catalog, explain any differences.

    13. Detectors in GC The ideal detector should:

    14. Flame Ionization Detector

    15. Thermal conductivity detector

    16. Thermionic Detector (NPD)

    17. Electron Capture Detector (ECD)

    18. Atomic Emission Detector

    19. Mass Spectrometer as a GC Detector

    20. Total Ion Chromatogram

    21. Selected (single) ion chromatogram:

    22. Connecting the GC to the MS This is difficult! Why?

    23. How is a GC interfaced to an MS? 1. Direct Connection

    24. How is a GC interfaced to an MS? (2) Open Split Interface

    25. Advantages of Open Split Design

    26. Jet Separator

    27. Cryogenic Focussing Technique for Beer Headspace Analysis

    28. Kovat’s Retention Index

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