APPLICATION OF THE RETENTION INDEX CONCEPT IN MICELLAR ELECTROKINETICCAPILLARY CHROMATOGRAPHY

The application of the retention index concept in micellar electrokine tic capillary chromatography (MECC) was evaluated for the identificati on of neutral species. Homologous series of alkylbenzenes and alkylary l 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 parti tion 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 line arly related to the surfactant concentration, whereas the retention in dex is independent of the surfactant concentration. The temperature de pendence of the retention index was investigated and the standard enth alpy, entropy, and Gibbs free energy for micellar solubilization of th e sample compounds were determined, showing that the hydrophobic inter action plays a significant role in MECC analysis.