Manipulation of separation selectivity in capillary zone electrophoresis of anionic solutes

This article discusses the main approaches to the manipulation of the separation selectivity of inorganic and low-molecular-mass anions in capillary zone electrophoresis (CZE). Physical or instrumental effects such as the detection mode, the sampling mode, the separation voltage, and the temperature are easy to control but their influence on selectivity is generally minimal, except for the use of selective detection. Selectivity effects arising from chemical parameters (i.e. effective size and charge, and structure of analyte; the pH, surfactant type and content, polyelectrolyte content, organic solvent content of the electrolyte; capillary treatment; and complexing agents) are much more significant than those resulting from physical effects. The effects on separation selectivity exerted by some of the above parameters can be complex, so that manipulation of selectivity in CZE of anionic solutes is often difficult. Nonetheless, many practical applications can be performed through the judicious control of parameters noted in this review. Some practical limitations to selectivity manipulation are highlighted and possible areas that can be studied in the future for selectivity control are noted.