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Gas & liquid chromatography (GLC), or the gas chromatography (GC), is a type of chromatography in which the mobile phase is a carrier gas, usually an inert gas such as helium or an un-reactive gas such as nitrogen, and the stationary phase is a microscopic layer of liquid or polymer on an inert solid support, inside glass or metal tubing, called a column. The instrument used to perform gas & liquid chromatographic separations is called a gas & liquid chromatograph. The glass & liquid chromatograph consists of five different units. These are the mobile phase supply system, the injection or sampling system, the column and column oven, the detector and the data acquisition and data processing system. Particularly in gas chromatography the mobile phase supply system is made of gas tanks, reducing valves, flow controllers and pressure gauges. In a typical liquid chromatographs the mobile phase supply system consists of a set of solvent reservoirs, sparred with helium gas to remove dissolved air, a solvent selector valve, a solvent programmer and a high pressure pump. In gas chromatography, the sampling system, in its simplest form, consists of a septum injector and a sampling syringe. In its more sophisticated form, it will include an automatic sampling device that may also be under the chromatograph computer control. Liquid chromatography sampling systems consist of a high pressure sample valve that may also have the sample supplied to the valve from an automatic sampling device. |
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