Stripping voltammetric detection of trace heavy metals using gold ultramicroelectrode arrays

The sensitive and simultaneous detection of zinc (Zn), cadmium (Cd) and lead (Pb) at gold ultramicroelectrode arrays (UMEAs) is reported. The device performance was based on the square-wave anodic stripping voltammetric technique. This consisted of the co-deposition of a layer of bismuth (Bi) together with the heavy metal target analytes onto the UMEA surface by applying a constant negative potential of -1.3 V for 360 s, followed by the stripping of the heavy metal alloy deposited by an anodic potential scan in a suitable potential window. Peaks at potentials ca. -1.0, -0.75 and -0.5 V were recorded and could be ascribed to the Zn, Cd and Pb stripping processes, respectively. Measurements were carried out in standard 0.1 M acetate buffer solutions pH 4.5, containing increasing concentrations of the three analytes. By using the peak areas, the corresponding calibration curves were constructed. The results showed a good sensitivity with a linear range from 10 to 70 ppb and a limit of detection of 7.5 ppb Pb, 5.3 ppb Cd and 9.2 ppb Zn, respectively.