We have studied a central composite design for the chiral separation of amphetamines using capillary electrophoresis. Five variables, i.e., buffer concentration, pH, chiral selector concentration, temperature, and applied voltage, were investigated. Enantiomeric resolutions as well as analysis time and generated power were established as responses for each experiment. A model of each response was obtained by multiple regression of a quadratic-degree mathematical expression. From the models, we determined the most favorable conditions for the chiral separation by optimizing the resolution and setting the other responses at threshold values. Results were compared with a previous study in which a systematic investigation of the operating parameters was carried out. In order to visualize the robustness of the method, response surfaces were drawn for the significant variables. We have concluded that experimental designs offer a rapid means of optimizing several variables and provide an efficient test for the robustness of the analytical method.

The separation by capillary electrophoresis of five ecstasy derivatives has been evaluated by means of experimental designs. A full-factorial design and a central composite design were employed to optimize the experimental conditions for a fast separation. With a conventional capillary (62.5 cm length) analytes were separated in less than 8 min. When the capillary length was reduced the analysis time decreased substantially. Comparisons were made between different procedures (e.g. working at a constant field or at constant voltage) and finally, a fast separation of five Ecstasy derivatives was achieved in 1 min

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