MEASUREMENT OF THERMODYNAMIC QUANTITIES OF MICELLAR SOLUBILIZATION BY MICELLAR ELECTROKINETIC CHROMATOGRAPHY WITH SODIUM DODECYL-SULFATE

Micellar electrokinetic chromatography (MEKC) allows the calculation of distribution coefficients between a micelle and the surrounding aqueous phase from the measurement of the migration time, provided the critical micelle concentration (CMC) and the phase ratio are known. Thermodynamic quantities such as enthalpy and entropy changes of micellar solubilization were calculated from the temperature dependence of the distribution coefficients. Sodium dodecyl sulfate (SDS) was employed to prepare a micellar solution and its CMCs and partial specific volumes at different temperatures were measured. The relationship between the molecular structures of solutes and the resulting thermodynamic quantities was investigated. The temperature inside the capillary was calculated from the temperature dependence of the distribution coefficient.