ADSORPTION-ISOTHERMS IN PROTEIN CHROMATOGRAPHY COMBINED INFLUENCE OF PROTEIN AND SALT CONCENTRATION ON ADSORPTION-ISOTHERM

The distribution coefficient (K) of a protein in ion-exchange chromato graphy is dependent on the protein and salt concentration in the mobil e phase. Conventional isotherms only describe the relationship between the mobile phase and stationary phase concentrations of the protein, the influence of salt being neglected. In this paper, the dependence o f K on salt is described by transition functions [phi(I)] such as logi stic dose response and hyperbolic tangent functions. The relationship between K and protein concentration is described by conventional isoth erms; the K value is considered as the first derivative of the isother m, or as the ratio between concentrations in the mobile and stationary phases. The stationary phase concentration can be expressed as a func tion of the mobile phase concentration. Combinations of these function s with transition functions can be used to approximate the binding cha racteristics of a protein dependent on protein and salt concentration.