gas chromatographyArticle Free Pass gas chromatography, in
analytical chemistry, technique for separating chemical
substances in which the sample is carried by a moving gas stream
through a tube packed with a finely divided solid that 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. Gas chromatography is also used to monitor
industrial processes automatically: gas streams are analyzed
periodically, and manual or automatic responses are made to
counteract undesirable variations. Many routine analyses are
performed rapidly in medical and other fields. For example, by
the use of only 0.1 cubic centimetre (0.003 ounc