CHROMATOGRAPHIC BAND PROFILES AND BAND SEPARATION OF ENANTIOMERS AT HIGH-CONCENTRATION

Experimental band profiles for large sample sizes of both single compounds and various binary mixtures of the optical antipodes of A-benzoylalanine are obtained on immobilized bovine serum albumin (BSA). The two enantiomers are resolved on this stationary phase. In the case of mixtures, the individual elution profiles are acquired by continuous fraction collection, followed by chromatographic analysis of these fractions. The equilibrium isotherms of each of the two chiral isomers between the two phases of the chromatographic system are determined by frontal analysis on the same column. These isotherms can be accounted for with great precision by a model assuming the existence of two kinds of sites on the stationary phase. For each isomer, the adsorption on each type of site is well described by a Langmuir equation. The first type of site is selective and interacts more fervently with the D isomer. The second type of site is not chiral selective, and the corresponding Langmuir isotherms are identical for the two isomers. The experimental profiles are nearly identical with the profiles calculated by the semi-ideal model of nonlinear chromatography, using the competitive Langmuir isotherms derived from the measured single-component isotherms. © 1990, American Chemical Society. All rights reserved.