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 James and 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 generators instead of gas tanks.

6. The second unit
It contains a manual ( )or an automatic injector.
It is situated inside a thermostatically controlled enclosure.
We use a syringe to 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 column Capillary 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

12. The bridge circuit for TCD detector

13. FID: Flame Ionization Detector

14. ECD: Electron Capture Detector

15. FPD: Flame Photometric GC Detector

16. NPD: Nitrogen Phosphorus Detector