Optimization of preparative ion-exchange chromatography of proteins: Linear gradient separations

In this study, the Steric Mass Action (SMA) model of ion exchange is employed in concert with appropriate mass balance equations to predict the separation performance of preparative ion-exchange chromatography. The model is able to accurately predict linear gradient separations of the proteins alpha-chymotrypsinogen A, cytochrome c, and lysozyme under overloaded conditions. The optimization behavior of preparative ion-exchange chromatography is examined under conditions of baseline resolution and induced sample displacement. This work demonstrates that a simple iterative procedure can be employed to establish optimal gradient conditions for preparative ion-exchange chromatography of proteins. The results also indicate that under appropriate conditions, sample displacement can be employed to dramatically improve the production rate with minor losses in product yield or purity. Linear gradient separations with sample displacement are also less sensitive to the adsorption properties of the feed stream than baseline resolved separations, resulting in simplified methods development.