CAPILLARY ZONE ELECTROPHORETIC SEPARATION OF THE ENANTIOMERS OF DIPEPTIDES BASED ON HOST-GUEST COMPLEXATION WITH A CHIRAL CROWN-ETHER

The enantiomeric separation of racemic glycyldipeptides and diastereomeric dipeptides by using capillary zone electrophoresis and (+)-18-crown-6-tetracarboxylic acid (18C6H(4)) as a chiral selector added to the electrolyte is described. The separation of dipeptides with two stereogenic centres into four peaks by using capillary zone electrophoresis is reported for the first time. Chiral discrimination is attributed to the formation of a diastereomeric host-guest complex which leads to different interactions for each enantiomer. Owing to the differences in stability of the complexes, the four optical isomers elute at different migration times, allowing the chiral separation. The influence of buffer composition, crown ether concentration and the addition of organic modifiers was studied. All glycyldipeptides were resolved and for most of the diastereomeric dipeptides four baseline-separated peaks were observed.