Influence of the nature of the buffer on chiral separation in capillary electrophoresis

The capillary electrophoretic separation of the enantiomers of a number of anionic sulfonamides was studied. Enantioselectivity of a range of native and modified cyclodextrins was tested. Also, from the experimental results, equilibrium constants and complex mobilities in different electrolyte systems were determined. In the present study it was found that the nature of the co-migrating buffer anion may significantly influence the magnitude of equilibrium constants, depending on the type of modification of a specific cyclodextrin. Consequently, this may also strongly influence the optimum cyclodextrin concentration for a particular separation. The results of the separation of sulfonamide enantiomers with cyclodextrins do not agree with the theoretical model suggested by Wren and Rowe, concerning the existence of a maximum in the mobility difference between two optical isomers.