Experimental design methodologies to optimize the CE separation of epinephrine enantiomers

A capillary electrophoretic method using a chiral selector was optimized by experimental design for the enantioresolution of epinephrine enantiomers. Two ?-cyclodextrins derivatives, namely heptakis-2,6-di-O-methyl?- cyclodextrin and carboxy-methyl-?-cyclodextrin, respectively neutral and charged, were used as chiral selectors employing an uncoated capillary. By using a statistical experimental design in which all factors are varied at the same time, it was possible to optimize the method with regard to the resolution between peaks and the two migration times. A fractional factorial design and a central composite design were used. A compromise between conflicting goals, such as maximization of resolution and minimization of analysis time, was found by means of a desirability function D. Balancing these goals against each other, the most acceptable solution to the problem was found and the optimized method gave a fast separation with complete resolution between the adrenaline enantiomers. The response surfaces obtained confirmed the robustness of the method.