PARAMETERS CONTROLLING THE ELUTION WINDOW AND RETENTION FACTORS IN MICELLAR ELECTROKINETIC CAPILLARY CHROMATOGRAPHY

The resolution of uncharged compounds in micellar electrokinetic capillary chromatography (MECC) is influenced by both the elution window and the retention factors of the compounds. The influence of the electroosmotic mobility and the effective mobility of the micelles on the elution window is treated theoretically and the effect of different experimental conditions on the elution window and the retention factors is determined. Although these variables cannot be controlled independently in many cases, the resolution in MECC can be improved by adjusting the composition of the applied electrolyte system. This is demonstrated for several electrolyte systems with different pH values, ionic strengths, surfactant concentrations and organic modifier contents. Further, the influence of the applied field strength, capillary surface modifications and the alkyl chain length of the surfactant are evaluated.