Fractionation

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.

[1][2] Fractions are collected based on differences in a specific property of the individual components.

Mixtures of liquids and gasses are separated by fractional distillation by difference in boiling point.

A typical protocol to isolate a pure chemical agent from natural origin is step-by-step separation of extracted components based on differences in their bioassay-guided fractionation physicochemical properties, and assessing the biological activity, followed by next round of separation and assaying.

Typically, such work is initiated after a given crude extract is deemed "active" in a particular in vitro assay.

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.
Differential centrifugation .