Study of protein binding to a silica support with a polymeric cation-exchange coating.

A silica-based, polyacrylate ion-exchange stationary phase has been prepared using Ce(IV) as the initiator. Analysis of the physical properties of the polymeric layer separated from the silica surface indicates that the polymeric coating is cross linked to some extent. The polymerization carried out at different concentrations of Ce(IV) demonstrated that the effective surface area can be increased by lowering the Ce(IV) concentration at higher monomer concentrations of the reaction mixture. These materials are quite reproducible and of high electrostatic binding capacity; 1.485 mumol/m2. The electrostatic binding capacity of a non-polymeric stationary phase reached the theoretical limit for a monolayer (0.16 mumol/m2). However, the covalent binding capacity of the same stationary phase was only 50% of the electrostatic binding capacity. The same trend was observed in all the polymeric stationary phases tested. This shows that the mechanism of protein binding in polymeric and conventional stationary phases is similar, and multilayer electrostatic binding is highly unlikely in these sorbents examined. Z numbers revealed that the contact area of the protein is independent of the polymeric character of the stationary phase and therefore, the increased loading of these polymeric stationary phases is due to the increased surface area.