TRACE-ELEMENT SPECIATION BY ANODIC-STRIPPING VOLTAMMETRY

The effects of a range of complexing agents and a detergent on the stripping process in anodic stripping voltammetry (ASV) were compared by using both differential-pulse and d.c. techniques. The detergent and most of the ligands, added after deposition was complete, seriously affected the height of the differential-pulse waves, and fulvic acid even decreased the area of the d.c. stripping peak. In order to obtain a correlation between ASV-labile metal measurements and bioassays, it is important that complexing agents in the sample solution affect only the deposition stage, and not the stripping stage in ASV. In order to achieve this result, the double acidification technique is recommended, where a voltammogram is recorded with deposition at the natural pH of the sample, but with stripping carried out at pH < 2, then a second voltammogram run on the same solution, but with both deposition and stripping effected at pH < 2. Excellent agreement was obtained between ASV-labile metal measured by the double acidification method and algal assays for a variety of natural and synthetic waters.