Orthogonal array design experiments for optimizing the separation of various pesticides by cyclodextrin-modified micellar electrokinetic chromatography

The potential of cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) for the separation of complicated environmental samples of pesticides and the applicability of orthogonal array designs (OADs) for the optimization of separation in CD-MEKC were investigated. Six relevant factors were investigated: type and concentration of cyclodextrin, concentration and pH of buffer, and concentration of micelle and organic modifier. In the first experiment, five factors were examined at two levels using an OA(9) (2(15)) matrix, by which the effect of each factor was estimated using individual contributions as response function. Based on the results of the first experiment, three most important factors were chosen for further optimization using OA(9) (3(4)) matrix to locate more exact levels for each variable. Finally, main-effect curves were used to predict approximate optimum conditions under which adequate separation of 15 pesticides was achieved within 30 min. (C) 1998 Elsevier Science B.V.