INVESTIGATION OF DISPLACER EQUILIBRIUM PROPERTIES AND MOBILE-PHASE OPERATING-CONDITIONS IN ION-EXCHANGE DISPLACEMENT CHROMATOGRAPHY

One of the major advantages of displacement chromatography is the simultaneous concentration and purification that can be effected during the process. The steric mass-action model of non-linear ion-exchange chromatography is employed to investigate the affects of mobile phase salt concentration and displacer equilibrium properties on the concentration of proteins in isotachic displacement zones. The results indicate that the salt microenvironment in displacement zones plays a major role in determining the concentration of the displaced proteins. The parameters which affect the salt microenvironment are both the initial salt concentration in the carrier as well as the induced gradient produced during the displacement process. For a given breakthrough volume, the induced gradient is determined by the ratio of the steric factor to the characteristic charge of the displacer. These results indicate that the use of relatively low salt concentrations in the carrier along with displacers with relatively high steric factor to characteristic charge ratios will produce significant concentration of the proteins during the purification process.