Gas Chromatography is a technique for separating chemical substances that relies on differences in partitioning behavior between a flowing mobile phase and a stationary phase to separate the components in a mixture.
The sample is carried by a moving gas stream through a tube packed with a finely divided solid or may be coated with a film of a liquid. Because of its simplicity, sensitivity, and effectiveness in separating components of mixtures, gas chromatography is one of the most important tools in chemistry. It is widely used for quantitative and qualitative analysis of mixtures, for the purification of compounds, and for the determination of such thermochemical constants as heats of solution and vaporization, vapour pressure and activity coefficients.
Two types of gas chromatography are encountered: gas-solid chromatography (GSC) and gas-liquid chromatography (GLC). Gas-solid chromatography is based upon a solid stationary phase on which retention of analytes is the consequence of physical adsorption. Gas-liquid chromatography is useful for separating ions or molecules that are dissolved in a solvent. If the sample solution is in contact with a second solid or liquid phase, the different solutes will interact with the other phase to differing degrees due to differences in adsorption, ion-exchange, partitioning or size. These differences allow the mixture components to be separated from each other by using these differences to determine the transit time of the solutes through a column.
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