INTERPRETATION OF MIGRATION BEHAVIOR OF INORGANIC CATIONS IN CAPILLARY ION ELECTROPHORESIS BASED ON AN EQUILIBRIUM-MODEL

In capillary ion electrophoresis, the migration of inorganic cations i n an aqueous-organic medium is influenced by complexation and interact ions between the solutes and organic solvents. This can be accounted f or by multiple chemical equilibria. Based on these equilibria, a migra tion model is proposed that describes the electrophoretic mobility of the cations in terms of absolute mobility, complex formation constants and the concentrations of complexing reagents and organic solvent. It was validated in a background electrolyte composed of imidazole, 2-hy droxyisobutyric acid (HIBA), 18-crown-6 and methanol. The parameters i n this model were estimated experimentally and were in good agreement with the values in the literature. The model is useful for predicting the mobilities as a function of the concentrations of HIBA, 18-crown-6 and methanol, and consequently facilitates selectivity optimization.