A gas chromatograph consists of a flowing mobile phase, an injection port, a separation column containing the stationary phase, a detector, and a data recording system.
Mobile phases are generally inert gases such as helium, argon, or nitrogen.
The injection port consists of a rubber septum through which a syringe needle is inserted to inject the sample.
The injection port is maintained at a higher temperature than the boiling point of the least volatile component in the sample mixture.
Since the partitioning behavior is dependent on temperature, the separation column is usually contained in a thermostat-controlled oven.
Separating components with a wide range of boiling points is accomplished by starting at a low oven temperature and increasing the temperature over time to elute the high-boiling point components.
Most columns contain a liquid stationary phase on a solid support. Separation of low-molecular weight gases is accomplished with solid adsorbents.