Chromatography is the collective term for a set of laboratory techniques used to separate mixtures. Chromatography involves passing a mixture dissolved in a “mobile phase” through a second substance, a “stationary phase”, separating the analyte to be measured from the other molecules in the mixture based on differential partitioning between the mobile and stationary phases. The nature of the two phases determines the rate of travel of the substances and this is how they are separated- referred to as the retention time.
Chromatography may be preparative or analytical. The purpose of preparative chromatography is to separate the components of a mixture for further use (and is thus a form of purification). Analytical chromatography is normally performed with smaller amounts of material and is for measuring the relative proportions of analytes in a mixture.