EVALUATION OF 3,5-DIMETHYLPHENYL CARBAMOYLATED ALPHA-CYCLODEXTRIN, BETA-CYCLODEXTRIN, AND GAMMA-CYCLODEXTRIN AS CHIRAL STATIONARY PHASES FOR HPLC

Optical resolving power of chiral stationary phases (CSPs) containing 3,5-dimethylphenyl carbamoylated beta-cyclodextrin chemically bonded to silica was compared with those of two commercial stationary phases containing carbamoylated beta-cyclodextrin (beta-CD), Cyclobond I SN and Cyclobond I DMP. For most of examined 14 racemates, higher selectivities were obtained on our CSPs than on the commercial CSPs. This may be ascribed to the higher degree of substitution of carbamate groups on beta-CD and to the opposite orientation of the immobilized beta-CD on our materials. The present CSPs were evaluated under reverse, normal and supercritical fluid chromatographic conditions. The highest selectivities were usually obtained under normal phase chromatographic conditions. The influence of cyclodextrins, alpha-, beta- and gamma-CD, on the enantioselectivity was compared. Each CSP containing different cyclodextrin showed the highest enantioselectivity for different racemates. By using silica particles with different average pore size (60, 100 and 300 angstrom), the influences of the amount and surface concentration of immobilized carbamoylated beta-CD on the enantioselectivity were studied for similar amounts of immobilized beta-CD. Higher enantioselectivity was observed for the material with high surface concentration.