THE EFFECTS OF COMPLEXING AGENTS AND SURFACTANTS ON THE DEPOSITION AND STRIPPING PROCESSES IN DIFFERENTIAL PULSE ANODIC-STRIPPING VOLTAMMETRY OF METALS AT THE HANGING MERCURY DROP ELECTRODE

An analysis scheme is presented that separates the individual effects of complexing agents and surfactants on the deposition and stripping steps in trace metal determination by differential pulse anodic stripping voltammetry (DPASV) at a hanging mercury drop electrode. The method involves DPASV measurements of total and electroactive (ASV‐labile) metal in pH 7.0 phosphate buffer before and after medium exchange, with and without acidification of the sample solution. Copper, lead, and cadmium were determined in the presence of Triton X‐100, a nonionic detergent, and the complexing agents fulvic and humic acids. Both the complexing agents and the surfactant affected deposition more than stripping, although Triton X‐100 had a significant effect on the stripping process. Triton X‐100 also acted as a complexing agent towards copper. Application of the analysis scheme to pristine and polluted freshwater samples showed that the decrease in the electroactivity of copper and lead was principally caused by the effect of surfactants on deposition. This study underlined the limitations of high‐frequency ASV techniques (e.g., DPASV) at a hanging mercury drop electrode for the determination of the toxic fraction of metals in water samples and raised questions about the usefulness of ASV copper complexing capacity titrations for water toxicity investigations. Copyright © 1990 VCH Publishers, Inc.