CAPILLARY ELECTROCHROMATOGRAPHY WITH MOLECULAR IMPRINT-BASED SELECTIVITY FOR ENANTIOMER SEPARATION OF LOCAL-ANESTHETICS

Preparation of stationary phases of predetermined selectivity for use in capillary electrochromatography by molecular imprinting was studied . Molecular imprinting of the local anaesthetic (S)-ropivacaine in met hacrylate-type polymers was done using an in situ photo-initiated poly merisation process. Such stationary phases could separate the enantiom ers of ropivacaine and the enantiomers of the structural analogues mep ivacaine and bupivacaine. The influence of several parameters on the a bility of the resultant imprinted capillary column to resolve mc-ropiv acaine was investigated. These parameters included the type and amount of functional and cross-linking monomers, the molar ratio of the impr int molecule to the monomers and the type of the porogen. The polymer- based, monolithic capillary columns could be rendered super-porous by the use of 1-25% isooctane as a porogenic agent. The best resolution w as obtained for polymers made using trimethylolpropane trimethacrylate as the cross-linking monomer. The enantiomer separation increased wit h increasing molar ratio of the functional monomer methacrylic acid to (S)-ropivacaine, however, at the expense of peak broadening. Initial studies on the optimisation of the electrolyte composition showed that the separation increased for electrolytes as the volume ratio of acet onitrile to buffer increased, the temperature raised and the pH became higher. (C) 1997 Elsevier Science B.V.