OPTIMIZATION OF STEP GRADIENT SEPARATIONS - CONSIDERATION OF NONLINEAR ADSORPTION

Nonlinear adsorption plays an important role in determining the chroma tographic behavior of proteins in preparative ion-exchange chromatogra phy. In this article, the steric mass action (SMA) isotherm is used in conjunction with a mass transport model to describe nonlinear cation- exchange chromatography. Excellent agreement is observed between simul ated and experimental step gradient separations of the proteins alpha- chymotrypsinogen A, cytochrome C, and lysozyme. A systematic method of selecting the optimum step gradient program for a given separation pr oblem is presented and employed to study optimization of step gradient chromatography under conditions of high mass loading. This article in cludes consideration of the effects of the adsorption properties of th e feed stream, the feed stream concentration, protein solubility, and other constraints on the optimum separation conditions. (C) 1995 John Wiley and Sons, Inc.