Nafion-coated bismuth film electrodes for the determination of trace lead and cadmium in herbal medicines by anodic stripping voltammetry

A novel analytical procedure for the determination of Pb(II) and Cd(II) in herbal medicines by differential pulse anodic stripping voltammetry (DPASV) on Nafion-coated bismuth film electrode (NCBFE) was proposed and experimentally validated. Various experimental parameters, which influenced the response of the NCBFE to these metals in real samples, were optimized. The results showed that there were well-defined peaks of Pb and Cd in herb samples at deposition potential of -1.2V and deposition time of 300 s. The analytical performance of the NCBFE was evaluated in the presence of dissolved oxygen, with the determination limits of 0.35 μg·L^-1 for Pb and 0.72 μg·L^-1 for Cd and recoveries of 87.8%-105.4% for Pb and 89.5%-108.5% for Cd obtained from different samples. The Pb and Cd concentrations in the studied samples have been also determined by graphite furnace atomic absorption spectrometry (GFAAS), suggesting that there was a satisfactory agreement between the two techniques, with relative errors lower than 6.5% in all cases. The great advantages of the proposed method over the spectroscopic method were characterized by its simplicity, selectivity and short analysis time, simultaneous analysis of different metals and cost-efficiency.