Comparisons of the separations of some neutral analytes by LC, MEKC, and CEC

The relative utility of high-performance liquid chromatography, micellar electrokinetic chromatography (MEKC), and capillary electrochromatography (CEC) is examined for the separation of essentially uncharged solute mixtures. Three model systems are used for which separations by reversed-phase liquid chromatography had been established. These consisted of a set of three substituted hydroxybenzoates; a mixture of six structurally closely related steroids; and the multicomponent aminoglycoside antibiotic, teicoplanin. These sets represented a range of difficulty in achieving separations by reversed-phase LC. It was found that equivalent or better separations for all systems could be established by MEKC and CEC. Both electrophoretic techniques offer much higher peak efficiencies than LC, and MEKC is found to be superior to CEC in terms of peak efficiencies and ruggedness of operation.