Liquid chromatography is an analytical method that uses selective absorption to separate the components of a mixture in solution. This method uses a moving solvent, a means of producing solvent motion (such as gravity or a pump), a means of sample introduction, a fractioning column, and a detector.
Improvements allow operation in three separation modes:
- liquid-solid partition, in which separations depend on relative solubilities of sample components in two immiscible solvents (usually one is water);
- liquid-solid absorption, where the differences in polarities of sample components and their relative absorption on an active surface facilitate the degree of separation; and
- molecular size separations, which relies on the effective molecular size of sample components in solution.
Examples of common solvents are hexane, isooctane, tetrahydrofuran, methyl ethyl ketone, acetone-chloroform, and toluene.
Examples of common packing materials are silica gel, polystyrene gel, ion exchange resins, alumina, and glass beads.