LIGAND-EXCHANGE CHROMATOGRAPHY OF FREE AMINO-ACIDS AND PROTEINS ON POROUS MICROPARTICULATE ZIRCONIUM-OXIDE

The Lewis acid sites present on the underlying zirconium oxide particles are responsible for the unusual elution sequence for amino acids on copper(II) loaded, phosphated zirconium oxide supports reported in an earlier study. To more thoroughly examine the effect of these strong Lewis acid sites, we have studied ligand exchange chromatography on copper(II) loaded zirconium oxide particles. It is shown here that carboxylate functional groups on amino acid solutes strongly interact with surface Lewis acid sites. Addition of competing hard Lewis bases to the eluent attenuates these specific interactions. The result is a chromatographic system with high selectivity which is also suitable for ligand exchange chromatography of proteins.