Electrochemical co-detection of As(III), Hg(II) and Pb(II) on a bismuth modified exfoliated graphite electrode

The applicability of a bismuth modified exfoliated graphite (EG) electrode for the co-detection of heavy metal ions -As(III), Hg(II) and Pb(II)-in water samples using square wave anodic stripping voltammetry (SWASV) is reported. Bismuth nanoparticles were deposited on an EG electrode potentiostatically at -1000 mV for 300 s to form EG-Bi electrode. The Bi modified EG electrode was characterised in 5 mM ferrocene and used to as an electrochemical sensor for Pb(II) and Hg(II) individually in 0.1 M acetate buffer solution (pH 5) with detection limits (LODs) of 0.83 μg L^-1., 0.46 μg L^-1 and limit of quantification of 2.8 μg L^-1 and 1.5 μg L^-1 respectively. Simultaneous detection of Pb(II), As(III) and Hg(II) was also performed with LODs of 0.053 μg L^-1, 0.014 μg L^-1, 0.081 μg L^-1 and LOQs of 0.18 μg L^-1, 0.047 μg L^-1 and 0.27 μg L^-1 for Pb(II), As(III) and Hg(II) respectively. All the detections were performed under optimised experimental conditions. The stability of the EG-Bi sensor was tested and the electrode was applied to environmental samples. The results found with this method were comparable with those obtained with inductively coupled plasma - optical emission spectrometric technique.