ORTHOGONAL ARRAY DESIGN AS A CHEMOMETRIC METHOD FOR THE OPTIMIZATION OF ANALYTICAL PROCEDURES .5. 3-LEVEL DESIGN AND ITS APPLICATION IN MICROWAVE DISSOLUTION OF BIOLOGICAL SAMPLES

The theory and methodology of a three-level orthogonal array design as a chemometric method for the optimization of analytical procedures we re developed. In the theoretical section, firstly, the matrix of a thr ee-level orthogonal array design is described and orthogonality is pro ved by a quadratic regression model. Next, the assignment of experimen ts in a three-level orthogonal array design and the use of the triangu lar table associated with the corresponding orthogonal array matrix ar e illustrated, followed by the data analysis strategy, in which signif icance of the different factor effects is quantitatively evaluated by the analysis of variance (ANOVA) technique and the percentage contribu tion method. Then, a quadratic regression equation representing the re sponse surface is established to estimate each factor that has a signi ficant influence. Finally, on the basis of the quadratic regression eq uation established, the derivative algorithm is used to find the optim um value for each variable considered. In the application section, mic rowave dissolution for the determination of selenium in biological sam ples by hydride generation atomic absorption spectrometry is employed, as a practical example, to demonstrate the application of the propose d three-level orthogonal array design in analytical chemistry.