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Gas chromatography

Instrumental Analysis. Gas chromatography. Jack Lee E.P. Department. Introduction. GC: Gas Chromatography GC was invented by A. J. P. Martin. The first gas chromatographic separation was a series of fatty acids.

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Gas chromatography

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  1. Instrumental Analysis Gas chromatography Jack Lee E.P. Department

  2. Introduction • GC: Gas Chromatography • GC was invented by A. J. P. Martin. • The first gas chromatographic separation was a series of fatty acids. • A more sophisticated GC was constructed by Jamesand Martin in 1955.

  3. The Modern GC • The modern gas chromatograph is a really complex instrument mostly computer controlled. • The samples are mechanically or manually injected. • The analytical results are automatically calculated and printed out.

  4. Block diagram of GC structure

  5. The first unit • It provides all the necessary gas supplies. • A minimum of three different gases would be required. (FID) • Three flow controllers, three flow monitors would be required. • A microprocessor is employed to monitor flow rates, adjust individual gas flow rates. • Use gas generatorsinstead of gas tanks.

  6. The second unit • It contains a manual (1. 2. 3)or an automatic injector. • It is situated inside a thermostaticallycontrolled enclosure. • We use a syringeto inject sample onto the column. • Automatic injector(carousel) can carry out a series of sample preparation procedures before injecting the sample onto the column.

  7. The third unit • It contains the column and an oven. • The column is the essential device to achieve the necessary separation. • The oven is used to control the column temperature. • The column has two kinds: Packed columnCapillary column

  8. The fourth unit • It contains the detector which is situated in its own oven. • There is a wide range of detectors available each having unique operating parameters and its own performing characteristics. • The output of detector is electronically modified.

  9. The detectors • Types of the detectors: TCD: Thermal Conductivity Detector FID: Flame Ionization Detector ECD: Electron Capture Detector FPD: Flame Photometric GC Detector NPD: Nitrogen Phosphorus Detector • Principles of the detectors

  10. TCD:Thermal Conductivity Detector

  11. The bridge circuit for TCD detector

  12. FID: Flame Ionization Detector

  13. ECD: Electron Capture Detector

  14. FPD: Flame Photometric GC Detector

  15. NPD: Nitrogen Phosphorus Detector

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