Gas chromatography is used for analytes that are easily vaporized. The sample is injected, vaporized, and swept onto a column filled with a stationary phase by a carrier gas.

If the stationary phase is a nonpolar coating on a solid support, interactions between the stationary phase and the analytes are weak. The analytes dissolve in the high molecular mass stationary phase which acts like an ideal solution. The concentration of the analyte in the gas phase above the stationary phase is proportional to the vapor pressure of the analyte and the mole fraction that is present in the stationary phase. Low boiling analytes with high vapor pressures elute first. These nonpolar coatings are commonly used for both packed columns and capillary columns.

Temperature of the column must be carefully controlled because the vapor pressure of all components increase with temperature but not exactly the same. Components elute more rapidly in narrower bands at higher temperatures.

Several different types of detectors are used with GC including flame ionization, electron capture, and mass spectrometry.

The analyst optimizes conditions for a separation by controlling mobile phase pressure, temperature, and stationary phase as discussed here.

Gas chromatography.