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Gas Chromatography (GC)

Department of Chemistry, Faculty of Science Universiti Teknologi Malaysia ______________________________ Analytical Chemistry Course. Gas Chromatography (GC). Hashim and Mohd Daniel Department of Chemistry, Faculty of Science Universiti Teknologi Malaysia 81310 Skudai, Johor, Malaysia.

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Gas Chromatography (GC)

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  1. Department of Chemistry, Faculty of Science Universiti Teknologi Malaysia ______________________________ Analytical Chemistry Course Gas Chromatography (GC) Hashim and Mohd Daniel Department of Chemistry, Faculty of Science Universiti Teknologi Malaysia 81310 Skudai, Johor, Malaysia marsin@kimia.fs.utm.my

  2. Outline • Introduction to GC • Instrumentation • Injector • Oven • Columns • Applications

  3. Gas Chromatographic equipment

  4. GC • Gas chromatography is a chromatographic technique that uses a gas as the mobile phase and either a liquid or solid as the stationary phase. • The analytes are adsorbed or dissolved in the stationary phase due to an equilibrium based on the vapor pressure and other additional interactive forces. • The mobile phase in GC is referred to as the carrier gas because ther is little interaction between the analyte and the gas phase. • Gas-solid chromatography (GSC) uses a solid stationary phase while gas-liquid chromatography (GLC) uses a liquid stationary phase that is bonded or coated onto a solid support.

  5. Pressure regulator Work Station Valve Detector Injector Column Oven Integrator/Plotter Carrier gas GC Instrument A schematic diagram of a capillary gas chromatograph.

  6. Detector Two-stage regulator Injector Carrier gas Integrator/Plotter or Work Station Column Oven GC Instrument A schematic diagram of a gas chromatograph.

  7. GC Instrument

  8. Gases for GC

  9. Split/splitless injector for GC Rajah 6.2 Gambarajah skema sejenis peranti untuk penyuntikan berpecah. Peranti ini juga boleh digunakan untuk penyuntikan tidak berpecah dengan pengawalan injap-injap berkenaan.

  10. Oven temperature Rajah 6.3 Contoh kitar suhu teraturcara bagi ketuhar kromatografi gas. Suhu isoterma

  11. Isothermal vs temperature-programmed GC Rajah 6.4 Pemisahan GC sebatian-sebatian n-alkana menggunakan turus HP-101 (metilpolisiloksana), 50 m x 0.32 mm I.D., ketebalan 0.3 m. (a) GC isoterma pada 140 oC. (b) GC suhu teraturcara 50 - 230 oC dengan kadar 4 oC minit1.

  12. GC Columns and stationary phases • Heart of the chromatographic system • Determine efficiency and selectivity

  13. GC columns: packed vs open tubular Rajah 6.5 Gambarajah skema turus terpadat dan turus tiub terbuka rerambut tipikal.

  14. Packed columns • Three components • Column tubing • Support material • Liquid stationary phase

  15. Column tubing • Criteria Inert, thermally stable, coil up • Types Copper, stainless steel, glass • Typical sizes 1-3 m long, 1/16, 1/8,1/4 inch OD, 2-3 mm ID • Inner surface silylated To reduce interaction with polar analytes

  16. Diatomite supportsurface Si O Si O Si OH OH OH Packing materials Rajah 6.7 Gambarajah skema menggambarkan keratan rentas contoh padatan yang terdiri daripada bahan penyokong yang tersalut dengan fasa cecair.

  17. Support materials • Criteria Unreactive towards analyte and liquid phase, uniform particles and pore size • Diatomaceous earths – Chromosorb • Particle sizes Analytical column: 80-100, 100-120 mesh Preparatory column: 40-60, 60-80 mesh • Chemical treatment AW – removes metallic impurities AW-DMCS – remove silanol groups

  18. Examples of GC support materials

  19. E.g.GC packing materials

  20. Non-diatomite support materials Porous Polymers - Porapak Polymers Chromosorb 101 (PSDVB), 103 (PS) Tenax Polymers - 2,6-diphenyl-p-phenylene oxide Carbopacks support - Inertness can be manipulated Adsorbents - Molecular sieve Silica gel - inertness can be manipulated Carbon molecular sieves

  21. Open tubular columns • No support material • Liquid phase coated on wall of column (WCOT) • Flexible fused silica Coated with polyimide layer Temp. < 350oC or else coating pyrolysed • ID: 0.1 – 0.75 mm • Film thickness: 0.1 – 5 m • Column length: 5-50 m • As ID and film thickness , sample capacity , but efficiency  • Typical analytical column: 25 m x 0.22 mm x 0.25 m

  22. Liquid phase requirements • High solubility • Differential solubility (high ) • Low vapour pressure (maximum • temperature) • Low viscosity (minimum temperature) • 10% vs. 5% : more plates, but 2 x tR • Use light loading (3%) for high boilers • Use heavy loadings (20%) for gases

  23. Non-polar liquid phases in GLC • Hydrocarbon phases: Squalane (C30H62), Apolene (C87 hydrocarbon), Apiezon L(-(CH2)n-) - Separation of non-polar molecules:n-alkanes • Alkylsilicone liquid phases: SE-30, OV-1, OV-101 • Dimethylsilicone (-(-Si(Me)2-O-)- polymer): BP-1, Ultra-1, DB-1

  24. GC on non-polar liquid phases 230 °C 2 °C/min 50 °C Hydrocarbons Essential oil (Cymbopogon nardus) Column: Ultra 1, 30 m x 0.25 mm x 0.25 mm

  25. Polar liquid phases in GLC • Substituted silicone liquid phases: methylphenyl silicone - OV-105, CP-Sil 58 • Ester liquid phases: - Poly(diethylene glycol adipate) DEGA - Poly(diethylene glycol succinate) DEGS • Polyether liquid phases: • Carbowax 200 to Carbowax 20M • (Polyethylene glycol, PEG) • - HP20-M, BP-Wax, BP20

  26. GC on polar liquid phase 230 °C Hydrocarbons 4 °C/min 50 °C Essential oil (Cymbopogon nardus) Column: HP-20M (Carbowax 20M)

  27. Other phases • Free fatty acid phase (FFAP) or • Carbowax 20M impregnated with terephthalic acid (Carbowax 20M-TPA): - Separation of free carboxylic acids C1 to C7 • Chiral liquid phases with amino acid derived centers • Separation of enantiomers - Chirasil-L-Val, Chirasil-D-Val - -Dex, -Dex, -Dex

  28. Liquid stationary phases

  29. Liquid stationary phases and applications

  30. Gas-solid chromatography

  31. Porous polymer phases

  32. Porous polymer phases

  33. Factors in selecting stationary phase • Nature of analyte • Stationary phase type • Column internal diameter • Film thickness • Column length

  34. Packed vs Open tubular columns

  35. Effect of column internal diameter (ID) Open Tubular Packed Column

  36. Column conditioning • Condition at A. 20 oC higher than analysis temp B. at least 10-20 oC less than stated max. operational temp of phase • Never condition at column’s max temp • Program temp slowly to conditioning temp (2-4 oC/min) • Cool down slowly (nonbonded phase) • Purge column with carrier gas for 1/2 hr before heating over • Very high carrier gas flows can be used for conditioning • Conditioning time varies with your need

  37. GC Applications • Petrochemical • Environmental • Pharmaceutical • Oleochemical • Others

  38. Thank you

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