The first utilization of graphene nano-sheets and synthesized Fe3O4 nanoparticles as a synergistic electrodeposition platform for simultaneous voltammetric determination of some toxic heavy metal ions in various real environmental water samples

An environmentally-friendly, inexpensive, and high-throughput method was developed for the simultaneous determination of three important heavy metal ions including Pb(II), Bi(III) and Cu(II). Those can cause synergistic toxicological effects in animals and humans. Magnetite (Fe3O4) nanoparticles were synthesized and characterized. A carbon paste electrode (CPE) modified with Fe3O4 NPs and graphene nanosheets (Fe3O4:Gr) was established. Its surface and electrochemical characterizations were described using scan electron spectroscopy (SEM), cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The charge transfer resistance values were 154.83, 77.71, 60.00 and 3.39 K omega for CPE, 5%(w/w) Gr/CPE, 2%(w/w) Fe3O4/CPE and [2%(w/w) Fe3O4:5%(w/w) Gr]/CPE revealing that the latter has greatly enhance electron transfer process. Following preconcentration by electrolytic deposition of such metal ions at [2%(w/w)Fe3O4:5%(w/w)Gr]/CPE at -0.7 V for 60 s in acetate buffer (pH 3.60), three distinguished anodic peaks were appeared at -0.55, 0.00 and 0.15 V due to oxidation of the deposited Pb, Bi and Cu, respectively. LOD values of 59, 44 and 55 ng L-1 for Pb(II), Bi (III) and Cu(II), respectively are much lower than the safety values set by World Health Organization in drinking water. This sensor displays good selectivity in presence of potentially interfering other metal ions, stability for 30 days with RSD of <= 5.25% and reproducibility of electrodes with R +/- RSD% of (98.94 +/- 1.28-99.67 +/- 1.12), (98.04 +/- 1.35-100.30 +/- 1.15) and (98.16 +/- 1.55-99.67 +/- 1.18) for Pb(II), Bi(III) and Cu(II), respectively. It was also applied successfully in trace determination of such polluted metal ions in real samples such as Tap water, some bottled natural water samples, river and seawater samples.