IN-FLOW SPECIATION OF COPPER, ZINC, LEAD AND CADMIUM IN FRESH-WATERS BY SQUARE-WAVE ANODIC-STRIPPING VOLTAMMETRY .2. OPTIMIZATION OF MEASUREMENT STEP

The measurement unit of an automatic system for in situ determination of dissolved Zn2+, Cd2+, Pb2+ and Cu2+ in fresh waters with square wav e anodic stripping voltammetry (SWASV), is described. The effect of su pporting electrolyte solution concentration, pre-electrolysis potentia l, metal deposition time and thickness of the Hg-film was studied by m eans of a full factorial experimental design and the significativity l evels were determined by a multifactorial ANOVA. Subsequently, the par ameters were optimized by using a sequential modified simplex method. Under the so found experimental conditions, the effects of foreign ion s and of dissolved oxygen have been investigated, the stability of cal ibration curves have been studied and the detection limits determined.