HISTAMINE-MODIFIED BETA-CYCLODEXTRINS FOR THE ENANTIOMERIC SEPARATIONOF DANSYL-AMINO ACIDS IN CAPILLARY ELECTROPHORESIS

Two novel monosubstituted beta-cyclodextrins (CD) bearing the histamin e moiety linked to the upper CD rim, either through the amino group or the imidazole nitrogen N-1, CD-hm and CD-mh, were successfully used a s chiral selectors in capillary electrophoresis for the enantiomeric d iscrimination of dansyl (Dns)-amino acids. Good results were obtained by using low concentrations of the selectors (1-3 mM). The effect of p H on the chiral discrimination was studied in order to modulate the nu mber and the position of the positive charges. By increasing the pH fr om 5 to 7.5, chiral discrimination decreased along with the deprotonat ion of the imidazolyl moiety. Inversion of the migration order was obs erved with the two CDs, depending on the relative position of the char ged moieties on the upper rim. Ion pair interaction coupled to inclusi on complexation seems to account for the discrimination process. The e ffects of the temperature, CD concentration and capillary length on ch iral resolution were also examined.