“…The principal groups of chromatographic methods are frequently subdivided with respect to the mechanism of the sorption process-for example, adsorption at a solid-liquid interface (adsorption chromatography), adsorption at a solid-gas interface (gas chromatography) (9,64,77,110,111,181,185), adsorption at a liquid-gas interface (foam analysis) {17, 128), adsorption at a liquid-liquid interface {163), distribution between two immiscible liquids (partition chromatography) {74, 118, 163), distribution between a gas and a liquid (gas-liquid partition chromatography) (76), distribution between a chemically reactive substance and a solution (particularly, ion exchange chromatography) (90,91,118), and partition between a liquid and a resin containing the same liquid (ion exclusion chromatography) {177). This classification of the chromatographic methods is subject to great variation, not only because the mechanism of the sorption process often varies with the experimental conditions, but also because several mechanisms may be effective simultaneously.…”