Gas Pressure Regulator and Flow Meter

The various carrier gas used in GC along with their characteristic features are stated below  

H2 It has a distinctly better thermal conductivity and lower density. Demerits are its reactivity with unsaturated compounds and hazardous explosive nature, 

He It has an excellent thermal conductivity, low density, inertness and it permits greater flow rates. It is highly expensive, 

Air It is employed only when the atmospheric 02 is beneficial to the detector separation. 

Importantly, the operating efficiency of a chromatograph is directly dependent on the maintenance of a highly constant carrier gas-flow-rate. Carrier gas passes from the tank through a toggle value, a flow meter, a few feet of metal capillary restrictors, and a 0-4 m pressure gauze. The flow rate could be adjusted by means of a needle value mounted on the base of the flow meter and is controlled by the capillary restrictors. On the downstream side of the pressure regulator, a tee (T) may split the flow and direct it to the sample and the reference side of the detector. 

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