Determination of effective mobilities and chiral separation selectivities from partially separated enantiomer peaks in a racemic mixture using pressure-mediated capillary electrophoresis.

A new measurement principle has been developed for the rapid determination of the effective mobilities of enantiomers from their partially separated peaks. The method involves (i) partial separation of the enantiomers of a racemic sample by electrophoresis, (ii) pressure mobilization of the partially separated band by the detector, (iii) calculation of the effective separation distance between the enantiomer centroids from the observed band width and the extent of theoretical band broadening, and (iv) calculation of the effective mobilities of the enantiomers (and the separation selectivity) from the effective separation distance. Experimental conditions that lead to negligible nonideal ionic contributions to the band width are outlined. The proposed method eliminates the error caused by the changing electroosmotic flow, yields complexation constant and ionic mobility values that are more precise than the conventionally obtained ones, and reduces the measurement time by 80-90%. The equations required for the calculations are presented in a simple, ready-to-use spreadsheet format.