Orthogonal array designs for the optimization of liquid chromatographic analysis of pesticides

Orthogonal array desings were applied to the optimization of liquid chromatographic analysis of pesticides used in golf courses. Three variables related to the composition of the mobile phase were studied: the percentage of acetonitrile, percentage of methanol, and the buffer pH. In the first experiment, each variable was tested at three levels using an OA9 (34) matrix, in which the interactions between the parameters were temporarily neglected. Based on the results of the first experiment, the second experiment was carried out following a two-level orthogonal array design with an OA8 (27) matrix, in which more exact levels for each variable were chosen, and the interaction effects were considered separately. Finally, the optimum conditions for liquid chromatographic analysis of the pesticides were proposed. The advantages and the disadvantages of three-level and two-level orthogonal array designs were discussed.