Bismuth-coated carbon electrodes for anodic stripping voltammetry

Bismuth-coated carbon electrodes display an attractive stripping voltammetr ic performance which compares favorably with that of common mercury-film el ectrodes. These bismuth-film electrodes are prepared by adding 400 mu g/L ( ppb) bismuth(III) directly to the sample solution and simultanously deposit ing the bismuth and target metals on the glassy-carbon or carbon-fiber subs trate. Stripping voltammetric measurements of microgram per liter levels of cadmium, lead, thallium, and zinc in nondeaerated solutions yielded well-d efined peaks, along with a low background, following short deposition perio ds. Detection limit of 1.1 and 0.3 ppb lead are obtained following 2- and l 0-min deposition, respectively, Changes in the peak potentials (compared to those observed at mercury electrodes) offer new selectivity dimensions, Sc anning electron microscopy sheds useful insights into the different morphol ogies of the bismuth deposits on the carbon substrates, The in situ bismuth -plated electrodes exhibit a wide accessible potential window (- 1.2 to -0. 2 V) that permits quantitation of most metals measured at mercury electrode s (except of copper, antimony, and bismuth itself). Numerous key experiment al variables have been characterized and optimized, High reproducibility wa s indicated from the relative standard deviations (2.4 and 4.4%) for 22 rep etitive measurements of 80 mu g/L cadmium and lead, respectively, Such an a ttractive use of "mercury-free", environmentally friendly electrodes (with a performance equivalent to that of mercury ones) offers great promise to c entralized and decentralized testing of trace metals.