Chromatography is a powerful device for separating compounds, allowing easier identification. In chromatography, compounds are separated by their relative affinity between a stationary phase and a mobile phase.
GC is a column chromatographic technique. The mobile phase is a chemically non-reactive gas like nitrogen or argon; the stationary phase is a thin film of a very high boiling organic liquid.
GC has a number of advantages. It has a high resolution; closely-related compounds can be separated. Many suitable stationary phases are available; and GC can be used to separate many, but not all classes of organic compounds. Once separation has been completed, several sensitive detectors are available. Perhaps most important, because the mobile phase is a gas, GC can be combined with mass spectroscopy (MS).
MS in itself constitutes a family of sophisticated analytical techniques; we previously discussed static and dynamic Secondary Ion MS. GC/MS is a two-dimensional separation technique, allowing more definitive resolution of components of complex mixtures. However GC and GC/MS are not universal techniques; and only on prime time television are unambiguous results successfully obtained in a pro-forma manner.
For successful GC, the analytical chemist has to have an understanding of the likely components of the mixture. Compounds must be sufficiently volatile that they are in the gas phase during injection. The temperature has to be appropriately and precisely controlled during elution. In liquid chromatography, the liquid mobile phase chemical is sometimes gradually changed during the separation process for complex mixtures; in GC, temperature programming can be used to separate mixtures with widely varying boiling points.
From: “Contamination Control In and Out of the Cleanroom”
