1. Introduction to Gas Chromatography Written by Bette Kreuz Produced by Ruth Dusenbery University of Michigan-Dearborn 2000

2. Introduction zGas chromatography is an instrumental method for the separation and identification of chemical compounds.

3. Slide 1a A sample is heated injector, zintroduced into a heated injector, separating column inert gas, and zcarried through a separating column by an inert gas, and zdetectedas a series of peaks on a recorder zdetected as a series of peaks on a recorder when components leave the column.

4. Slide 1

5. Slide 2a zThe instrument used for our experiments, a Varian 3350 gas chromatograph, is shown here.

6. Slide 2 Carrier gas/ Regulator Varian 3350 Gas Chromatograph Computer Controls for Method and Output

7. Slide 3a stationary phasemobile phase zChromatographic separation involves the use of a stationary phase and a mobile phase. differentially attracted to the stationary phasemove through the stationary phase at different rates zComponents of a mixture carried in the mobile phase are differentially attracted to the stationary phase and thus move through the stationary phase at different rates.

8. Slide 3 T=0 T=10’ T=20’ Injector Detector Most Interaction with Stationary Phase Least Flow of Mobile Phase

9. Seperation zSeparation of the components of the mixture occurs in the column. zCompounds differentially retained in the stationary phase reach the detector at different times to produce a set of peaks along the time line.

10. Slide 4a In gas chromatography mobile phaseinert carrier gas zthe mobile phase is an inert carrier gas and stationary phasesolidliquid coated on a solid zthe stationary phase is a solid or a liquid coated on a solid contained in a coiled column.

11. Slide 4

12. Slide 5a zColumns can be short, large diameter packed column or long, very small diameter capillary columns. zEach has its own use and associated advantages and disadvantages.

13. columns

14. Slide 5

15. Packed column

16. Capillary column

17. Slide 6a zThe mobile phase or carrier gas flows through the instrument from a pressurized tank. zFlow rate is controlled by a two stage regulator on the gas tank and additional controls within the instrument.

18. Slide 6 Two Stage Tank Regulator GC Flow Controller

19. Flow controlers

20. Slide 7a zThe column is contained in a heated oven that is preceded by a heated injector port and followed by a heated detector unit which produces the output. zA set of preprogrammed parameters regulate the operation of the system.

21. Slide 7

22. Slide 8a zThe injector, column oven and detector components of the Varian 3350 gas chromatograph are shown here.

23. Slide 8 Injector Detector Column in Oven

24. Slide 9a separationmethod zPreprogrammed parameters, called a separation method, control the operation of the system.

25. Temperature program oven or run isothermally

26. Slide 9 Control Panel sets Separation Method

27. Slide 10a zSamples may be pure compounds. zHowever, they are often prepared as dilute solutions due to the sensitivity of the detection methods.

28. Slide 10 Dilute Solution Pure Sample

29. Slide 11a zWhen the system is ready, as indicated by the ready light, samples are injected into the injector port where they are vaporized and carried into the column by the carrier gas.

30. Slide 11 10  l Syringe

31. Liquid injector

32. HP auto injector

33. Different injection methods

34. Gas sample loops

35. 6 port valve

36. Gas sampling port

37. Slide 12 Packed Column installed in Oven Compartment. Exit to Detector Enter from Injector

38. Slide 13a zThe detector response is sent to a computer system where the progress of the sample is monitored on the computer monitor in graphical form that displays detector response as a function of run time.

39. FID

40. Flame Ionization detectors

41. Low Fid response

42. Slide 14a retention time zEach component of the mixture reaches the detector at a different time and produces a signal at a characteristic time called a retention time. area under a peak amount of that component zThe area under a peak is related to the amount of that component present in the mixture.

43. Slide 14

44. Slide 15a zThe detector information can also sent to a printer that produces hard copy of the chromatographic run.

45. Slide 16a In the printout of the chromatographic analysis: number of peaksnumber the number of peaks correlates with the number of components of components in the sample, area under each peak the area under each peak correlates with the relative amount of that component relative amount of that component in the sample, and if standard information is available, the retention time retention time under defined conditions can be identify used to identify each component.

46. Slide 16