A technique in which a biospecific adsorbent is prepared by coupling a specific ligand (such as an enzyme, antigen. or hormone) for the macromolecule of interest to a solid support (or carrier). This immobilized ligand will interact only with molecules that can selectively bind to it. Molecules that will not bind elute unretained. The retained compound can later be released in a purified state. Affinity chromatography is not a chromatographic technique as such, but is actually selective filtration.