Gas chromatographyGas chromatography

Instrumental Instrumental AnalysisAnalysis

Jack LeeJack LeeE.P.E.P. Department Department

IntroductionIntroduction

• GC:GC: Gas Chromatography Gas Chromatography• GC GC was invented by A. J. P. Martin.A. J. P. Martin.• The first gas chromatographic

separation was a series of fatty acids.• A more sophisticated GC was

constructed by JamesJames and MartinMartin in 1955.1955.

The Modern GCThe 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 calculated and printed printed outout.

Block diagram of Block diagram of GC GC structurestructure

The first unitThe 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.

The second The second unitunit

• It contains a manualmanual ( (1. 2. 3). 2. 3)or an automatic injectorautomatic injector..

• It is situated inside a thermostaticallythermostatically controlled enclosure.

• We use a syringesyringe to inject sample onto the column.

• Automatic injector(carouselcarousel) can carry out a series of sample preparation procedures before injecting the sample onto the column.

The third unitThe 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 columnPacked column Capillary Capillary

columncolumn

The fourth unitThe fourth unit

• It contains the detector which is situated in its own ovenoven.

• 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.

The detectorsThe detectors

• Types of the detectors: TCD:TCD: Thermal Conductivity Detector Thermal Conductivity Detector

FID:FID: Flame Ionization Detector Flame Ionization Detector ECD:ECD: Electron Capture Detector Electron Capture Detector FPD:FPD: Flame Photometric GC Detector Flame Photometric GC Detector NPD:NPD: Nitrogen Phosphorus Detector Nitrogen Phosphorus Detector• Principles of the detectors

TCD:TCD: Thermal Conductivity Thermal Conductivity DetectorDetector

The bridge circuit for TCD The bridge circuit for TCD detectordetector

FID:FID: Flame Ionization Flame Ionization DetectorDetector

ECD:ECD: Electron Capture Electron Capture DetectorDetector

FPD:FPD: Flame Photometric GC Flame Photometric GC DetectorDetector

NPD: Nitrogen Phosphorus Detector