A simple model of enantioselective adsorption on chiral stationary phases

In this paper, we consider a simple Monte Carlo (MC) model of adsorption of a pair of enantiomers on a chiral stationary phase. In the proposed model, the surface of the stationary phase is assumed to consist of two kinds of sites: chiral receptors, that are responsible for the selective differentiation between the components of a racemic mixture, and the "background" nonselective sites. Accordingly, each of the chiral receptors is characterized by two different values of the adsorption energy, depending whether the adsorbed molecule is complementary to the receptor or it is not. On the other hand, the same value of the adsorption energy is attributed to each nonselective site, regardless of the type of the isomer adsorbed. In addition, lateral interactions in the adsorbed phase are taken into account. The influence of the receptor concentration on the adsorption isotherms and the associated selectivity is examined. The obtained results indicate that the adsorption/separation of enantiomers is considerably influenced by both lateral interactions and chiral receptor concentration. In particular, it is shown that strong attractive/repulsive interactions in the adsorbed phase may deteriorate/improve the separation even when the number of the chiral receptors is increased. (C) 2003 Elsevier B.V. All rights reserved.