Gas chromatography is the process of separating compounds in a mixture by injecting a gaseous or liquid sample into a mobile phase, typically called the carrier gas, and passing the gas through a stationary phase. The mobile phase is usually an inert gas or an nonreactive gas such as helium, argon, nitrogen or hydrogen. The stationary phase is a microscopic layer of viscous liquid on a surface of solid particles on an inert solid support inside a piece of glass or metal tubing called a column. The surface of the solid particles may also act as the stationary phase in some columns. The glass or metal column through which the gas phase passes is located in an oven where the temperature of the gas can be controlled and the eluent coming oﬀ the column is monitored by a computerized detector.
A gas chromatograph is made of a narrow tube, known as the column, through which the vaporized sample passes, carried along by a continuous ﬂow of inert or nonreactive gas. Components of the sample pass through the column at diﬀerent rates, depending on their chemical and physical properties and the resulting interactions with the column lining or ﬁlling, called the stationary phase. The column is typically enclosed within a temperature controlled oven. As the chemicals exit the end of the column, they are detected and identiﬁed electronically.