Use of quasi-equimolar, closely-spaced, poly-co-ion background electrolytes in capillary electrophoresis for the reduction of electromigration dispersion over a wide mobility range

Abstract

The dependence of analyte peak shape and separation efficiency as a function of the mobility spacing of the co-ions was investigated by computer simulation of the electrophoretic process in poly-co-ion background electrolytes. The simulation results indicated that when the mobilities of the strong electrolyte co-ions differed from each other by less than 1·10 −5 cm 2 V −1 s −1, much of the electromigration dispersion could be eliminated for the analytes that migrated in the mobility window of the co-ion pair. Accordingly, a poly-component, quasi-equimolar mixture of polyethyleneglycol monomethyl ether hydrogensulfates was synthesized in which the effective mobilities of the strong electrolyte anions ranged from about 10·10 −5 to 23·10 −5 cm 2 V −1 s −1, and the effective mobilities of these anions differed from each other by about 0.5·10 −5 to 1.5·10 −5 cm 2 V −1 s −1. A comparison of the electropherograms of the same seven-component sample obtained with a single co-ion background electrolyte and the poly-co-ion background electrolyte (at identical ion strength) verified that the quasi-equimolar, poly-co-ion background electrolyte eliminated much of the peak distortion that was caused by electromigration dispersion and resulted in good separation efficiencies over the entire, broad mobility range covered by the new poly-co-ion background electrolyte.