Kinetic Study of Solute Permeation across Surfactant Micelle/Bulk Solvent Interface by Moment Analysis - Chromatographic Capillary Electrophoresis (MA-CCE)

We applied moment analysis (MA) with chromatographic capillary electrophoresis (CCE) to the analytical determination of rate constants (kin and kat) of solute permeation at the interface between a bulk solvent and surfactant micelles. CE experiments were carried out in the MEKC system using thymol and sodium dodecylsulfate (SDS) as the solute and surfactant, respectively, under CCE conditions. In CCE mode, experimental conditions are controlled so that the migration of micelles, which dissolve single or plural solute molecules, is stopped in the axial direction of a capillary. Only solute molecules migrate in the capillary and are detected to record elution peak profiles. The mass-transfer kinetics of solute molecules in the capillary are determined from the elution peak profiles by the MA theory. The values of k(in) and k(out) were respectively determined as 1.5 x 10(-6) and 2.6 x 10(-9)m s(-1) for the permeation of thymol molecules at the interfacial boundary of SDS micelle. It was demonstrated that MA-CCE was effective for the kinetic study of solute permeation across the interface between a bulk solvent and spherical molecular aggregates, e.g., surfactant micelles.