fractionation

thumb|right|Fractional distillation apparatus using a Liebig condenser. A [[conical flask is used as a receiving flask. Here the distillation head and fractionating column are combined in one piece.]] thumb|right|Differential centrifugation.

Fractionation is a separation process in which a certain quantity of a mixture (of gasses, solids, liquids, enzymes, or isotopes, or a suspension) is divided during a phase transition, into a number of smaller quantities (fractions) in which the composition varies according to a gradient. Fractions are collected based on differences in a specific property of the individual components. A common trait in fractionations is the need to find an optimum between the amount of fractions collected and the desired purity in each fraction. Fractionation makes it possible to isolate more than two components in a mixture in a single run. This property sets it apart from other separation techniques.