CHIRAL SEPARATION OF LOCAL-ANESTHETICS WITH CAPILLARY ELECTROPHORESIS- EVALUATION OF THE INCLUSION COMPLEX OF THE ENANTIOMERS WITH HEPTAKIS(2,6-DI-O-METHYL)-BETA-CYCLODEXTRIN

A chiral capillary electrophoresis system for the high resolution sepa ration of the enantiomers of the local anaesthetics mepivacaine, ropiv acaine, bupivacaine and prilocaine is described. Triethanolamine was a dded to the background electrolyte to obtain a negative electroosmotic flow and hence higher resolutions. The interactions of the local anae sthetics and their chemical analogues with the chiral selector, dimeth yl-beta-cyclodextrin, were studied. From a model describing chiral cap illary electrophoresis,the association equilibrium constants were dete rmined by curve-fitting. The separation of mepivacaine, ropivacaine an d bupivacaine was due to the different mobilities of the free analytes in solution, whereas the separation of a pair of enantiomers of a sin gle analyte was due to differences between the association equilibrium constants K-1 and K-2. Branching of the alkyl chain, which was situat ed close to the cavity in the inclusion complex, had strong effects on the chiral separation of the enantiomers.