Method development strategy for the analysis of anionic solutes by capillary electrophoresis

A systematic approach to the development of methodology for the analysis of anionic solutes by capillary electrophoresis (CE) has been implemented. The strategy allows a rapid optimization of the experimental conditions and is based on the following steps: 1) A near optimum pH is chosen by inspection of the effective mobility versus pH curves of the sample components. The optimum pH lies in a region where the differences in the mobilities of all solutes are maximal. 2) An electrolyte system is selected by comparing the effective mobility of the electrolyte with the effective mobility of the primary components of the studied mixture. The appropriate electrolyte has a mobility as similar as possible to the mobility of the major components of the sample. 3) An initial experiment is run with the selected electrolyte system adjusted to the chosen pH and input values for other instrumental variables and electrolyte characteristics. 4) Depending on the degree of resolution obtained in the initial run, two important variables, the applied voltage and the electrolyte concentration, are then tuned in the proper direction, favoring the achievement of the highest resolution at the lowest possible analysis time. The proposed method development strategy was validated experimentally with a mixture of short-chained carboxylic acids and inorganic anions.