ENANTIOMER SEPARATION OF ACIDIC RACEMATES BY CAPILLARY ELECTROPHORESIS USING CATIONIC AND AMPHOTERIC BETA-CYCLODEXTRINS AS CHIRAL SELECTORS

Enantiomer separations of various acidic racemates were performed by c apillary electrophoresis (CE) using a commercial cationic beta-cyclode xtrin (beta-CD), quaternary ammonium beta-CD (QA-beta-CD), and a comme rcial amphoteric beta-CD (AM-beta-CD) as chiral selectors, Eleven acid ic racemates were successfully separated using QA-beta-CD by changing the CD concentration and the buffer pH. These enantiomer separations w ere compared with the results using five neutral CD derivatives. Altho ugh most racemates were separated with some of the neutral CDs, relati vely high CD concentrations were required to obtain baseline separatio ns. In contrast, when QA-beta-CD was employed, the enantiomer separati ons were successful at low concentrations below 5 mM. Enantiomers of f ive acidic racemates and ten dansylated amino acids (Dns-amino acids) were separated using AM-beta-CD. Although the baseline separation of r acemic 4-chloromandelic acid was not achieved with either QA-beta-CD o r five neutral CDs, AM-beta-CD showed complete resolution. Furthermore , the simultaneous enantiomer separation of eight Dns-amino acids was also achieved with AM-beta-CD. Both QA-beta-CD and AM-beta-CD were ana lyzed by CE and mass spectrometry (MS) in order to identify their comp ositions because they consisted of a mixture having different degrees of substitution. QA-beta-CD consisted of six components having from on e to six quaternary ammonium groups. The composition of AM-beta-CD, ho wever, was very complicated and could not be identified. (C) 1997 Else vier Science B.V.