Micellar Electrokinetic Chromatography

Recently, capillary electrophoresis (CE) or high-performance capillary electrophoresis (HPCE) has become popular as a high-resolution separation method. The technique was first introduced by Mikkers et al. (1 ), Jorgenson and Lukacs (2 ), and Hjert�n (3 ), as an instrumental version of electrophoresis. Although CE can generally give a higher resolution within a shorter time compared with conventional high-performance liquid chromatography (HPLC), only ionic or charged solutes can be separated by CE, in principle. This was a serious limitation of CE, but the development of electrokinetic chromatography (EKC) (4 ) has been able to solve such problems. EKC is based on chromatographic principles using homogeneous solutions containing an ionic “carrier” and the same apparatus as CE. The unique characteristic of EKC is that both neutral and charged analytes can be separated electrophoretically. Among various modes of EKC, micellar EKC (MEKC) (5 –7 ), which uses micellar solutions of ionic surfactants, has become the most popular technique for the separation of small neutral molecules.