CHIRAL DISCRIMINATION BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH JOINT USE OF 2 CYCLODEXTRIN ADDITIVES

The diversity of adsorption properties of native and permethylated cyc lodextrins enabled us to propose a new advantageous chromatographic sy stem with two chiral selectors working jointly (system III). Fundament al information regarding the retention mechanism in such a system with two chiral additives is presented. Depending on the localisation of t he chiral complexation process three chromatographic systems have been designed and experimentally compared under the same chromatographic c onditions (solvent composition, temperature). Phenomenological and the oretical models of the above mentioned systems, where complexation occ urs in the mobile phase (system I), in the stationary phase (system II ) or in both phases together (system III), have been studied and exper imentally confirmed. Species of biological interest were used as model compounds. It has been found that almost always system III offers the best results, although all the investigated substances display differ ent chromatographic behaviour, i.e., adsorption on RP18 phase and comp lexation by native and permethylated cyclodextrin. The final enantiose lectivity coefficient (alpha(3)) may by predicted as a product of part ial coefficients(alpha(1), alpha(2)) according to the equation alpha(3 ) = alpha(1).alpha(2). (C) 1997 Elsevier Science B.V.