It is the most sensitive chromatographic technique, but is limited to compounds that are readily vaporised without decomposing. (Usually Molar mass of less than 300).
Gas chromatography is used in the detection of illegal drugs in athletes.
There are two types of GC: Gas-Liquid (GLC) and Gas-Solid Chromatography (GSC). They both work the same way.
• The mobile phase is a gas, usually nitrogen, called the carrier gas.
• A small amount of sample is injected into the top of the column through an injection port.
• The injection port is heated and the sample vaporises. The sample is swept into the column.
• In the column, the temperature is lower and the sample condenses and adheres to the stationary phase. The temperature is gradually increased and as the boiling points of components are reached, they are swept along with the carrier gas, adsorbing and desorbing along the way.
• The least soluble component (those least attracted to the solid or liquid stationary phase) are eluted first.