Characterization of non-linear adsorption properties of dextran-based polyelectrolyte displacers in ion-exchange systems

Experimental studies were carried out on the non-linear adsorption properties of dextran-based polyelectrolytes in anion- and cation-exchange chromatographic systems. By monitoring both the induced salt gradients and sequential breakthrough fronts, parameters were determined for use in a Steric Mass Action (SMA) model of non-linear ion-exchange chromatography. These parameters include: total ion capacity of the columns, characteristic charge, steric factor, equilibrium constant, and maximum adsorptive capacity for each of the polyelectrolytes. In addition the number of functional groups were determined by elemental analysis. The values of the SMA parameters were found to be independent of salt and polyelectrolyte bulk phase compositions. Parameters were also determined for a variety of proteins. Experimental isotherms for the polyelectrolytes and proteins were compared with those simulated by the SMA model. Finally, the implications of polyelectrolyte adsorption properties with respect to their ability to act as efficient displacers in ion-exchange displacement systems are discussed.