Optimization of ion-exchange displacement separations I. Validation of an iterative scheme and its use as a methods development tool

Displacement chromatography has been demonstrated to be a powerful, high-re solution preparative tool. The performance of displacement systems can be a ffected by a variety of factors such as the feed load, flow-rate, initial s alt concentration and the displacer partition ratio. Thus, the optimization of displacement separations is a uniquely challenging problem. In this man uscript, an iterative optimization scheme has been presented whereby one ca n identify the optimum operating conditions for displacement separations at a given level of loading on a given resin material. The solid film linear driving force model has been employed in concert with the Steric Mass Actio n formalism of ion-exchange chromatography to describe the chromatographic behavior in these systems. Simple pulse techniques have been employed to es timate the transport parameters. The iterative scheme has been validated us ing a rigorous Feasible Sequential Quadratic Programming algorithm. Finally , the utility of the iterative optimization scheme as a methods development tool for displacement separations has been demonstrated for a difficult se paration. The results indicate that the use of the optimization scheme lead s to significantly better performance than standard rules of thumb. (C) 200 0 Elsevier Science B.V. All rights reserved.