EFFICIENCY OPTIMIZATION IN CAPILLARY ELECTROPHORETIC CHIRAL SEPARATIONS USING DYNAMIC MOBILITY MATCHING

In order to obtain high separation efficiencies in capillary electroph oresis, electromigration dispersion has to be minimized either by usin g very dilute samples in concentrated background electrolytes or by ma tching the mobilities of the analyte and the co-ion of the background electrolyte. A dynamic mobility matching method is presented here that can be used advantageously in cyclodextrin-containing zwitterionic ba ckground electrolytes. A rigorous equilibrium model has been developed to describe the effective electrophoretic mobility of the co-ion of t he background electrolyte as a function of the analytical concentratio ns of the cyclodextrin, the zwitterionic buffer, and the hydronium ion . With adjustment of these parameters, either simultaneously or indivi dually, the co-ion mobilities can be easily varied over a 10-fold rang e. Using fenoprofen as an example, predictions of the model have been verified experimentally. The separation efficiency has been maximized by varying the analytical concentration of the zwitterionic buffer whi le the pH and the cyclodextrin concentration of the background electro lyte were kept constant to maintain the separation selectivity. The dy namically matched mobilities resulted in symmetric enantiomer peaks an d good separations.