14] Micellar electrokinetic chromatography

Abstract

Publisher Summary Terabe et al. first demonstrated the use and principle of micellar electrokinetic chromatography (MEKC) based on the suggestion made by Nakagawa. Since then, diverse applications of this method to various organic compounds have been reported. Although MEKC uses an electric field, as the driving force for the migration of analytes in a manner similar to capillary zone electrophoresis (CZE), the difference between MEKC and CZE lies, first, in its separation mechanism. Separation by CZE is based on the difference in electrophoretic mobility of ions. In contrast, MEKC uses the difference in the partition ratio of compounds between aqueous phase and micellar phase (more accurately, pseudostationary phase). Second, MEKC can separate not only ionic compounds but also nonionic compounds at the same time. Because the migration order of nonionic compounds and, in many cases, ionic compounds is determined by the degree of hydrophobic interaction, between micelles and analytes, the separation mechanism is more similar to that of the reversed-phase high-performance liquid chromatography (RP-HPLC) than to electrophoresis, except that MEKC achieves high theoretical plate numbers (>100,000) for many compounds routinely. The reason is, mainly, because there is a difference in the flow profile in a capillary tube from HPLC. MEKC is a powerful tool, especially for the separation of small molecules. This chapter concentrates on the practical aspects and the knowledge necessary to use MEKC.