Effect of surfactant structures on the separation of cold medicine ingredients by micellar electrokinetic chromatography.

Using micellar electrokinetic chromatography (micellar EKC or MEKC) the retention behavior of twelve active ingredients used in cold medicines was investigated. The role of five different anionic surfactants was investigated by MEKC and the results were compared with those obtained by conventional capillary zone electrophoresis (CZE). The relative retention order of the 12 ingredients was significantly different among the five surfactants; the different elution orders were ascribed to the differences in the hydrophilic groups of the surfactants. The effects of surfactant concentration and buffer pH were also investigated. The ingredients were successfully separated within 30 min by micellar EKC with high theoretical plate numbers (approximately 200,000), and selectivity was much improved in comparison with CZE. Micellar EKC was applied by the internal standard method to the quantitation of some active ingredients combined in commercial preparations.