Simultaneous determination of Cd and Pb in the environment using a pencil graphite electrode modified with polyaniline/graphene oxide nanocomposite

In this work, an applicable electrochemical sensor was developed for simultaneous determination of toxic heavy metal ions, Cd and Pb, in the environment, using a pencil graphite electrode (PGE) modified with polyaniline/graphene oxide/polyethylene glycol/cysteine nanocomposite (MGO-PANI). The MGO-PANI-PGE was prepared simply by scanning the PGE potential in a solution containing the MGO-PANI suspension. Cd and Pb ions were detected with high sensitivity on the modified electrode by monitoring their characteristic reduction peaks. Enhanced sensitivity was achieved through the strong affinity interaction of the metal cations with N groups on PANI, and the presence of three-dimensional functionalized graphene oxide providing a high specific surface area on the modified PGE. Detection limits for Pb and Cd ions were determined from the first calibration curves of differential pulse voltammograms as 0.12 +/- 0.02 and 0.65 +/- 0.05 ppb, respectively. The cations were determined simultaneously without significant changes in the height of the peaks in both the absence and presence of a known concentration of the other ion. The practicality of the MGO-PANI-PGE for simultaneous determination of Cd and Pb ions in real-water samples was evaluated by analysing spiked Cd and Pb ions in the Zarrineh River of Miandoab City. High reproducibility, nearly complete recovery, and no significant contamination of the electrode surface in the vicinity of the real-water sample were observed. A remarkable advantage of this work is the use of cheap and available pencil lead, as well as the one-step, simple modification of the electrode surface for simultaneous analysis of Cd and Pb in the environment.