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/ SplitlessSplitSplitless Want to reproducibly get in & get out Sample focusSample focus

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 AdvantagesDisadvantages

9. HO-CH 2 -CH 2 -(O-CH 2 -CH 2 ) n -OH polyethylene glycol

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