Gas chromatography (GC) , is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition . Typical uses of GC include testing the purity of a particular substance, or separating the different components of a mixture (the relative amounts of such components can also be determined). In some situations, GC may help in identifying a compound. In preparative chromatography , GC can be used to prepare pure compounds from a mixture. [