Application of response surface methodologies in capillary electrophoresis

Abstract

A fast method of determining ascorbic acid and isoascorbic acid by capillary zone electrophoresis with a photodiode array detector was developed. Response surface methodologies based on three-level, three-variable designs, such as the Box-Behnken design, central composite face-centered and full fractional design, were used comparatively for optimization of buffer pH, buffer concentration and operation voltage. Statistical interpretation of the variables concerning different responses, such as resolution and migration time of the last migrated analyte, were performed. The optimum conditions of these variables were predicted using a second-order polynomial model fitted to the results obtained by applying three designs. The response surface plots using three experimental designs revealed a separation optimum with Tris–HCl buffer of pH 8.5, a concentration of 50 mM, and an operation voltage of 30 kV. The significance of the statistical designs were confirmed by the generally good agreement obtained between predicted responses and actual experimental data. We concluded that experimental designs offer a rapid means of optimizing several variables and provide an efficient test for the robustness of the analytical method.