The sample in the column is heated until the components vaporize. Because a specific type of molecule possesses a characteristic size and boiling point, each chemical compound is carried through the column at different times. Retention time is a specific behavior for every compound. Therefore, comparing sample RT with standard RT, the compounds are identified and quantified. Gas adsorption chromatography involves a packed bed comprised of an adsorbent used as the stationary phase.
Common adsorbents are zeolite, silica gel and activated alumina.
This method is commonly used to separate mixtures of gases. Gas-liquid chromatography is a more common type of analytical gas chromatography. In this type of column, an inert porous solid is coated with a viscous liquid which acts as the stationary phase. Diatomaceous earth is the most common solid used. Solutes in the feed stream dissolve into the liquid phase and eventually vaporize.