Microemulsion electrokinetic chromatography with different organic modifiers: separation of water- and lipid-soluble vitamins

Microemulsions prepared by using either sodium dodecyl sulfate (SDS) or trimethyltetradecylammonium bromide (TTAB) were tested with regard to the migration time, selectivity and number of theoretical plates using a set of both water-soluble and lipid-soluble vitamins. While in the separations where SDS was used as the surface-active agent for microemulsion preparation, better resolutions were obtained with both hydrophilic and lipophilic vitamins, with q-TAB the best separations were obtained with the micelle-forming reagent only or with diethyl ether as the microemulsion-forming component. In the SDS-based separations nicotinic acid was moving with the same velocity (relative to the endoosmotic flow) regardless of the emulsion or micellar phase used. It is proposed that owing to its behaviour it can serve as an ideal internal standard in further studies on microemulsion separations.