Define Adsorption chromatography - Basic Separation Technique?

Adsorption is surface interaction and is by number of forces, between surface atoms of solids and molecules of external solute. Adsorption chromatography comprises of systems where active absorption occurs at the surface of the solid stationary medium, often alumina or silica gel. Competition for adsorptive sites occurs between the molecules of the mixture to be separated and the molecules of mobile phase, be it gas or liquid.

The speed of migration of a component will depend on its adsorptive affinity relative to the other species present. A number of attractive forces (Vander Waal forces, hydrogen bonding etc.) between the stationary phase and substances to be separated have been recognized and separation takes place due to differences in these adsorption forces.