ORTHOGONAL ARRAY DESIGN AS A CHEMOMETRIC METHOD FOR THE OPTIMIZATION OF ANALYTICAL PROCEDURES .3. 5-LEVEL DESIGN AND ITS APPLICATION IN A POLAROGRAPHIC REACTION SYSTEM FOR SELENIUM DETERMINATION

The theory and methodology of a five-level orthogonal array design for the optimization of analytical procedures were developed. In the theo retical section, the construction and characteristics: of the OA(25)(5 (6)) matrix are described in detail while orthogonality is proved by m eans of a fourth-order polynomial model. Next, the assignment of exper iments in the OA(25)(5(6)) matrix is illustrated, followed by the data analysis strategy, in which significant/non-significant influence for each factor is quantitatively evaluated by the analysis of variance ( ANOVA) technique including the percentage contribution, and the differ ences among five levels for each factor that has a significant influen ce are determined by Duncan's multiple F-test, Finally, the response s urface methodology for the OA(25)(5(6)) matrix is developed by using t he equations obtained from the proof on orthogonality. In the applicat ion section, the reaction system for selenium determination by differe ntial-pulse polarography, as a practical example, is employed to demon strate the application of the OA(25)(5(6)) matrix in the area of analy tical chemistry.