Importance of heat of adsorption in modeling protein equilibria for overloaded chromatography

The heat of adsorption and its dependence on surface coverage has been measured calorimetrically for protein ion-exchange systems of bovine serum albumin and ovalbumin on an anion-exchanger. Experimental data show that protein adsorption is endothermic for both systems which suggests that the process is entropically driven. Also, heat of adsorption decreased with coverage indicating repulsive lateral interactions between adsorbed proteins. The protein adsorption isotherms were modeled with the nonideal surface solution model. This analysis revealed that it is essential to include the entropic contribution in modeling equilibrium behavior. An empirical method for incorporating this effect has been presented.