Orthogonal array design experiments for optimizing the separation of nine pesticides by micellar electrokinetic chromatography

Separation in micellar electrokinetic chromatography is influenced by many factors. The separation of 9 pesticides was optimized using orthogonal array designs (OADs), five relevant factors were investigated: type and concentration of surfactant, concentration of buffer, pH and concentration of urea modifier. In the first experiment, five factors were examined at two levels using an OA(16)(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 more important factors were chosen for further optimization using OA(9) (3(4)) matrix to locate the exact levels for each variable. Finally, 9 pesticides achieved baseline-separation within 15 min. (C) 2002 Elsevier Science B.V. All rights reserved.