<Tr> <Th> Related </Th> <Td> Thin layer chromatography High performance liquid chromatography </Td> </Tr> <Tr> <Th> Hyphenated </Th> <Td> Gas chromatography - mass spectrometry </Td> </Tr> <P> 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 . </P> <P> In gas chromatography, the mobile phase (or "moving phase") is a carrier gas, usually an inert gas such as helium or an unreactive gas such as nitrogen . Helium remains the most commonly used carrier gas in about 90% of instruments although hydrogen is preferred for improved separations . The stationary phase is a microscopic layer of liquid or polymer on an inert solid support, inside a piece of glass or metal tubing called a column (a homage to the fractionating column used in distillation). The instrument used to perform gas chromatography is called a gas chromatograph (or "aerograph", "gas separator"). </P>

What is the main data you can obtain from the gc chromatograms
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