GAS CHROMATOGRAPHY Gas chromatography is a technique of

GAS CHROMATOGRAPHY Gas chromatography is a technique of choice for the separation of thermally stable & volatile organic & inorganic compounds.

Instrumentations of gas chromatography 1. 2. 3. 4. 5. 6. Carrier gas Pressure gauge Sample injection system Column Detector Amplifier & Recorder

Instrumentation

1. Carrier Gas The purpose of the Carrier gas is to transport the sample through the column to the detector.

Properties of carrier gas Purity of carrier gas should be at least 99. 95% Chemically Inert and pure Higher Density Compatible with detector Cheap And Easily available The gas is usually passed through the column at the rate of 40 -80 cm 3/min. Commonly used gases are nitrogen , argon, helium, hydrogen & carbon dioxide

Sample Injection System The sample is injected by a hypodermic syringe through a self sealing silicon rubber septum on a glass liner with in a metal block, where it is vaporized and swept on to the column The carrier gas flow through the injector carrying vaporized solute Block is heated at fixed temp sufficently high to convert liquid sample into a “plug”of vapor (at least 50° above highest boiling component)

Sample Injection system

Type of column • 1. Packed column. • 2. Open tubular or capillary column.

B) Capillary column

Detectors For Gas Chromatography 1. 2. 3. 4. 5. 6. Thermal conductivity detector (TCD) Electron capture detector(ECD) Thermionic emission detector (TED) Flame ionization detector(FID) Flame photometric detector(FPD) Photoionization detector(PID)

Ideal characterteristic of detector Applicable to Wide range of wavelength. High sensitivity to even small Concentration. Rapid response. Linearity. Non destructive. Simple and easy to Maintain.

GC Recorder

HOW GAS CHROMATOGRAPHY MACHINE WORK ? • Vapourized sample is injected onto the chromatography columnn. Sample move through the column through the flow of innert gas. The component are recorded as a sequesce of peaks as the leave the column.