Chromatographic separation techniques are multistage separation procedures in which the components of a sample are distributed between two phases, one of which is stationary while the other is mobile. The stationary phase may be a solid or a liquid supported on a solid or a gel. The stationary phase may be packed in a column, spread as a layer, or distributed as a film, etc. The mobile phase may be gaseous or liquid or supercritical fluid. The separation may be based on adsorption, mass distribution (partition), ion exchange, etc., or may be based on differences in the physicochemical properties of the molecules such as size, mass, volume, etc.