ABSTRACT
Chromatographic separations depend on differences in the distribution of substances between two phases, one stationary and the other moving. Because chromatography is a multistage process, even small differences in affinity can be exploited to produce useful separations. The process of ligand exchange can be applied to analytical elution chromatography. F. Helfferich noted that the method could be applied to gas-liquid chromatography. A new development in liquid chromatography uses ligand exchange in the mobile phase. Ligand-exchange chromatography is a process in which complex-forming compounds are separated through the formation and breaking of labile coordinate bonds to a central metal atom, coupled with partition between a mobile and a stationary phase. Little use has been made of ligand exchange in gas chromatography, though labile metal-ligand complexes are exploited in gas chromatography of olefins on stationary phases carrying silver ions. If the metal-ligand bond is labile, one ligand can substitute for another.
