OPTIMIZATION OF THE ELECTROKINETIC SAMPLE INTRODUCTION IN CAPILLARY ELECTROPHORESIS FOR THE ULTRA-TRACE DETERMINATION OF ANIONS ON SILICON-WAFER SURFACES

A capillary electrophoretic method for the ultra trace determination o f anions on silicon wafer surfaces is presented. In several sets of ex periments designed according to the methodology of Taguchi, electrokin etic sample introduction with transient isotachophoretic preconcentrat ion was simultaneously optimized for peak height, peak area, peak asym metry, efficiency, peak resolution, and reproducibility of migration t ime and peak area. The blank reading of the method showed no cross con tamination. Thus, a detection limit of 10 nmol L-1 and a linear range from 50 to 500 nmol L-1 were obtained and verified by two independent instruments. Furthermore, the method was applied to the determination of anions on wafers from a regular production line wetting the whole w afer surface with ultrapure water. The capillary electrophoretic resul ts agree with those obtained by ion chromatography.