MICELLAR ELECTROKINETIC CHROMATOGRAPHY IN ZERO-ELECTROOSMOTIC FLOW ENVIRONMENT

Micellar electrokinetic chromatography (MEKC) is conducted in polyacry lamide-coated-capillaries under almost complete suppression of electro osmotic flow, The equations of migration and resolution for neutral so lutes in this mode of MEKC operation are presented. The technique is t ermed reversed-flow MEKC (RF-MEKC) because, in contrast to MEKC in bar e-silica capillaries (N-MEKC), solute migration order is reversed and solute migration time is inversely proportional to micelle concentrati on. This presents an advantage for the high-efficiency separation of e xtremely and moderately hydrophobic solutes in a short analysis time. Examples of the separation of polycyclic aromatic hydrocarbons, aflato xins and dansylated-amino acids are presented using sodium dodecyl sul fate (SDS) surfactant. Polycyclic aromatic hydrocarbons are separated using a relatively low micelle concentration. The detection sensitivit y for these compounds is enhanced in two ways, First, the peaks are sh arp because of the short analysis time and the inertness of the column surface, Second, the fluorescence background and Joule's heating are minimal because of the low concentration of SDS and other additives ne eded to affect the separation. While N-MEKC is mainly conducted with b asic buffers, RF-MEKC can be conducted in basic as well as acidic medi a as illustrated in the separation of 15 dansylated-amino acids at pH 4.2.