Effect of organic modifier concentrations on electrokinetic migrations in micellar electrokinetic chromatography

Abstract

The effect of low concentrations of organic modifiers on the electroosmotic mobility, μ_eo, and electrophoretic mobility of the micelle, μ_{ep, mc}, in micellar electrokinetic chromatography (MEKC) with sodium dodecyl sulfate (SDS) solutions was investigated. The results showed that μ_eo was mainly influenced by the viscosity of the running solution. A linear relationship between μ_eo and the concentration of the organic modifier was found in MEKC. A newly defined parameter, the mobility ratio, R_{m, mc}, which is the ratio of the electro-phoretic mobility of the micelle to the electroosmotic mobility, and which characterizes the surface charge density of the micelle in MEKC system with organic modifiers, was introduced. A linear relationship between R_{m, mc} and the organic modifier concentration was observed. The parameter R_{m, mc} was found to be useful to investigate the changes in the micellar phase with the addition of organic modifier. The measured μ_{ep, mc} values showed different and interesting characteristics among different organic modifiers.