Chromatography is a method used to separate different components of a mixture. The principle of chromatography is based on the entrainment of a dissolved sample by a mobile phase (also called eluent) through a stationary phase (also called fixed phase). Each molecule will be more or less rapidly entrained according to its affinity for, respectively, the stationary phase and the mobile phase, allowing the separation of the different constituents present.
Chromatography can be analytical (identification of the compounds present) or preparative (separation of the compounds from a mixture).
There are different types of chromatography which can be classified by the nature of the mobile phase (gas, liquid), the type of interaction (absorption, ion exchange, exclusion, affinity) or the type of support (column, paper).
Chromatography is faster with gas (GC) than with liquid (LC): a separation takes a few seconds or minutes with the former, a few minutes or hours with the latter. Moreover the detection sensitivity is better with the first one. The only limitation of this method is that the solute must be volatile, which is not always the case for organic substances. Moreover, the use of high temperatures induces risks of denaturation of organic compounds. However, the major problem remains the choice of the mobile phase.