High-performance liquid chromatography of proteins on alumina

Proteins can be separated on alumina with an aqueous mobile phase by ion-exchange and size exclusion chromatography and by a combination of both techniques. The pH dependence of the ion-exchange retention mechanism is explained on the basis of two similar concepts: the isoelectric point of the protein and the zero point of charge of the alumina surface. The possibility of infuencing the surface properties of alumina by the choice of the buffer anion lends great flexibility to the system. However, the size exclusion selectivity is limited owing to the small choice of presently available aluminas. Examples are given that demonstrate the advantages of alumina for the separation of strongly basic proteins at high pH.