Optimization of micellar electrokinetic capillary chromatography with solvent-gradients

The development of instrumentation permitting the application of solvent-gradients to micellar electrokinetic capillary chromatography (MECC) is presented. A computational method is also described that is capable of predicting retention times of solutes separated in this manner. Theoretical predictions are based on capacity factor, electroosmotic flow rate, and micellar flow rate data obtained by the separation (under isocratic conditions) of a test mixture of fluorescently-labeled alkylamines and polyaromatic hydrocarbons using differing concentrations of organic modifier in the mobile phase. Separations are performed using continuous concave-, linear-, and convex-shaped gradients, as well as the demonstration of the possibility of generating more obscure gradient shapes. Resultant solute retention times are shown to correlate reasonably well with values obtained from the theoretical model. A computational method for optimization of solvent-gradient MECC separations is also presented, based on the modified simplex method. This computer program is then utilized to optimize the separation of a group of polyaromatic hydrocarbons (PAH's). The instrumentation and methodologies developed enhance the power of MECC as a separation technique by broadening its applicability to more complex systems.