APPLICATION OF THE RETENTION INDEX CONCEPT IN MICELLAR ELECTROKINETIC CAPILLARY CHROMATOGRAPHY

The application of the retention index concept in micellar electrokinetic capillary chromatography (MECC) was evaluated for the identification of neutral species. Homologous series of alkylbenzenes and alkylaryl ketones were applied as retention index standards slid also for tl;e calculation of the micelle migration time by an iteration procedure. The relationship between retention indexes, I, and octanol-water partition coefficients is discussed, and Delta Ivalues were calculated from retention indexes, obtained with both anionic and cationic surfactant systems, to study the separation mechanism for solutes with different functionalities in MECC. The influence of the phase ratio is treated theoretically, and it is demonstrated that the capacity factor is linearly related to the surfactant concentration, whereas the retention index is independent of the surfactant concentration. The temperature dependence of the retention index was investigated and the standard enthalpy, entropy, and Gibbs free energy for micellar solubilization of the sample compounds were determined, showing that the hydrophobic interaction plays a significant role in MECC analysis.