Micellar electrokinetic chromatography of charged and neutral drugs in acidic running buffers containing a zwitterionic surfactant, sulfonic acids or sodium dodecyl sulphate separation of heroin, basic by-products and adulterants

A procedure for the separation of charged and neutral solutes in acidic micellar running buffers has been developed. The procedure is based on a zwitterionic surfactant 3-N,N-dimethylmyristylammoniopropanesulfonate (MAPS) and alkylsulfonates added to the running buffer at pH 4.0. The alkylsulfonates increase the migration-time window for elution of neutral substances by increasing electro-osmotic mobility and by creating a negative micellar electrophoretic mobility. The test solution contained opiates and adulterants found in heroin seizures. Both the test solution and actual heroin seizures were successfully separated using a running buffer containing 50 mM 6-aminocaproic acid adjusted to pH 4.0 with 50 mM MAPS, 5 mM 1-heptanesulfonic acid and 10% acetonitrile. The procedure offers an alternative to micellar electrokinetic chromatographic separations based on charged surfactants in alkaline buffers.