DIRECT AND INDIRECT CHIRAL SEPARATION OF AMINO-ACIDS BY CAPILLARY ELECTROPHORESIS

Two approaches to the chiral separation of racemic mixtures of amino a cids by means of capillary electrophoresis have been evaluated. These were indirect separation of diastereomers formed by derivatization wit h (+)- or (-)-1-(9-fluorenyl)ethyl chloroformate and direct chiral sep aration after derivatization with 9-fluorenylmethyl chloroformate. Sep aration conditions were optimized by the application of a full factori al design. For indirect separation, concentration of sodium dodecyl su lphate (SDS) and pH were the most important separation variables, and for direct separation, concentration of isopropanol (IPA), beta-cyclod extrin and SDS were the most prominent factors affecting separation. T he presence of IPA was a prerequisite for chiral recognition. With reg ard to selectivity, efficiency, analysis time and ease of method devel opment the best results were provided by the indirect method. It shoul d be noted, however, that the success of this approach is based on the availability of a derivatization reagent in high optical purity.