Gas chromatography varies from other types of chromatography in that the mobile phase is a gas that separates the materials as vapors.
Hence, it is used in the gas phase to separate and detect small molecular weight compounds.
The sample is either a vaporized gas or a liquid in the injection port. A carrier gas is the mobile process for gas chromatography, usually helium due to its low molecular weight and being chemically inert. Moreover, the pressure is applied and the analyte is pushed through the column by the mobile process. Separation is achieved using a stationary-phase coated column.
The gas chromatographic equilibrium is partitioning, and the sample components must partition (i.e. distribute) between the two phases: stationary phase and mobile phase.
Compounds with a greater affinity to the stationary phase spend more time in the column and therefore elute later and have a longer retention time (Rt) than compounds with a higher affinity for the mobile phase.
Stationary phase affinity is driven primarily by intermolecular interactions, and stationary phase polarity can be preferred to optimize interactions, and thus separation.
Ideal peaks are Gauussian distributions and symmetric due to the random nature of the column correlations between the analytes.
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