INFLUENCE OF COMPOSITION ON THE SELECTIVITY OF A MIXED-MICELLAR BUFFER IN MICELLAR ELECTROKINETIC CHROMATOGRAPHY

The solvation parameter model is used to study the influence of compos ition of mixed micelles containing sodium N-dodecanoyl-N-methyltaurine and the neutral polyether surfactant Brij 35 on selectivity in micell ar electrokinetic chromatography. The addition of Brij 35 to the anion ic surfactant affects mainly the phase ratio and reduces the hydrogen- bond acidity of the mixed micelle but otherwise has only minor influen ces on selectivity. The addition of organic solvent to the bulk electr olyte produces small and predictable changes in selectivity similar to those observed in reversed-phase liquid chromatography. An interphase model is suggested to account for the observed changes in retention c haracteristics of the mixed micelles.