Chromatography is a collection of techniques used to analyze and separate mixtures of compound in complex matrices. Chromatography is a system that consists of a stationary phase (usually solid material) and a mobile phase (gas or liquid). The sample is introduced in the mobile phase which passes over the stationary phase. Substances are separated due to their difference in interaction with the stationary phase. Compounds that adhere easily to the stationary phase will move slowly in the chromatographic system, compounds less adherent, will move faster and the different compounds will be separated. At the end of a chromatographic system there is a detector. GC detectors can be of various types, some general (multipurpose) or more specific depending on the compounds to analyze. In gas chromatography the stationary mobile phase is an inert gas (He, H2 and N2).
The stationary phase is embedded in a column and can be of various materials depending on your analytes. The column can a glass or metal tube that is packed with particles that hold the stationary phase, or more common a silica capillary that has a layer of stationary phase on its inside. The column is placed inside an “oven” that allows control the temperature of the column. The temperature can be held at a certain point, or the temperature can be varied (increased) to allow compounds with high boiling points to pass through the system. The upper limit of operation is given by the combination of thermal stability of compounds and simultaneously the need for vaporization of these with highest boiling points. GC detectors can be of various types, some general (multipurpose) or more specific depending on the compounds to analyze.