Voltammetric behavior and trace determination of lead at a mercury-free screen-printed carbon electrode

Abstract Screen-printed carbon electrodes (SPCEs), without chemical modification, have been investigated as disposable sensors for the measurement of trace levels of Pb. Cyclic voltammetry was employed to elucidate the electrochemical behavior of Pb at these electrodes in a variety of supporting electrolytes. For all of the electrolytes studied the anodic peaks obtained on the reverse scans, showed that the Pb had been deposited as a thin layer on the surface of the SPCE. The anodic peak of greatest magnitude was obtained in 0.1 M HCl. The possibility of determining Pb at trace levels using this medium was examined by anodic stripping voltammetry using the differential pulse waveform in the measurement step. Models are suggested for the deposition of Pb onto the SPCE surface under stated conditions. Calibration plots were found to be linear in the range 6.3 ngmL-1 to 24 ngmL-1 and 24 to 50 ngmL-1; the detection limit was 2.5 ngmL -1 and the coefficient of variation, determined on one single electrode, at a concentration of 12.6 ngmL-1 was calculated to be 2.4 % (n = 5). The effect of copper, cadmium and zinc on the Pb stripping peak was examined and, under the conditions employed, no significant change in current was found. The sensors were evaluated by carrying out Pb determinations on spiked and unspiked pond water. The recovery was calculated to be 97.4 % and the coefficient of variation was 3.2% at a concentration of 12.6 ngmL-1. These performance characteristics indicate that reliable data may be obtained for Pb measurements in natural waters