SEPARATION OF NEUTRAL AND BASIC ENANTIOMERS BY CYCLODEXTRIN ELECTROKINETIC CHROMATOGRAPHY USING ANIONIC CYCLODEXTRIN DERIVATIVES AS CHIRAL PSEUDO-STATIONARY PHASES

Separations of neutral and basic racemates were performed using five d ifferent anionic cyclodextrin (CD) derivatives as chiral selectors, vi z. carboxymethylated beta-CD, beta-CD phosphate sodium salt, sulfobuty l ether beta-CD sodium salt, carboxymethylated gamma-CD, and gamma-CD phosphate sodium salt, For the separation of neutral racemates, an unt reated fused silica capillary was employed and various neutral racemat es were successfully separated, Since the pH of the buffer affected th e electroosmotic flow (EOF), the resolution was improved by changing t he buffer pH, A polyacrylamide coated capillary was employed for the s eparation of basic racemates to suppress EOF and to prevent adsorption of cationic analyte on the capillary surface, By choosing an appropri ate type and concentration of anionic CD, about 40 basic racemates wer e successfully separated. Some rough binding constants of basic analyt es with an anionic beta-CD were measured to discuss the optimum concen tration of the CD. The migration direction was dependent on the bindin g constants and the concentration of the CD. The analyte strongly boun d to the anionic CD migrated towards the anode but the weakly bound on e moved towards the cathode, Anionic gamma-CDs were also very useful f or the separation of basic enantiomers. Five neutral CDs were employed as chiral selectors to compare selectivity between charged and neutra l CDs, and eleven racemates could only be resolved using anionic CDs, The separation of some basic racemates in human plasma was also descri bed, The direct injection of plasma samples was possible for some enan tiomers that did not interact strongly with plasma proteins.