Control of separation selectivity in capillary zone electrophoresis of inorganic anions

The control of the separation selectivity of anions in capillary zone electrophoresis is critically reviewed. Selectivity effects arising from the chemical environment of the analyte (that is, the pH, surfactant content and organic modifier content of the background electrolyte and the presence of complexing species) are shown to be more significant than those arising from physical effects, such as the sampling mode and the separation conditions. In general, the effects on separation selectivity exerted by these parameters are quite subtle, so that control of selectivity in capillary electrophoresis of inorganic anions is often quite difficult. Some practical limitations to selectivity control are highlighted and possible areas that can be studied in the future for selectivity variation are suggested.