Anodic stripping voltammetry of tungsten at graphite electrodes

Trace levels of tungsten can be determined at a graphite electrode using anodic stripping voltammetry. Tungsten is concentrated at the electrode surface after reduction to Wv as a insoluble ternary complex in the presence of rhodanide ions and antipyrine (ANT) or 4‐ dimethyl‐aminoantipyrine (pyramidon, PYR). The optimal conditions of this determination are: electrolyte 1 M H2SO4 containing 0.078 M NH4SCN + 0.04M ANT or 0.02M PYR; deposition potential −0.50 V; sweep from −0.4 to −0.05 V using differential pulse stripping technique. Detection limit is 1 × 10−9M (0.2 μg/L) for a 180 s accumulation time (with a relative standard deviation of 15%). Results obtained for waste waters, steel and olive leaves are reported.