In-flow speciation of copper, zinc, lead and cadmium in fresh waters by square wave anodic stripping voltammetry Part II. Optimization of measurement step

The measurement unit of an automatic system for in situ determination of dissolved Zn 2+, Cd 2+, Pb 2+ and Cu 2+ in fresh waters with square wave anodic stripping voltammetry (SWASV), is described. The effect of supporting electrolyte solution concentration, pre-electrolysis potential, metal deposition time and thickness of the Hg-film was studied by means of a full factorial experimental design and the significativity levels were determined by a multifactorial ANOVA. Subsequently, the parameters were optimized by using a sequential modified simplex method. Under the so found experimental conditions, the effects of foreign ions and of dissolved oxygen have been investigated, the stability of calibration curves have been studied and the detection limits determined.