Simultaneous Adsorptive Stripping Voltammetric Analysis of Heavy Metals at Graphenated Cupferron Pencil Rods

Electroanalysis of heavy metal ions in the presence of cupferron ligands has been extensively studied due to its ability to form stable metallic coordination complexes. Herein, electrochemically reduced graphene oxide (ERGO) sheets were for the first time employed in conjunction with low-cost, disposable pencil graphite rods and in situ plated thin mercury films (HgF) for the simultaneous detection of Cd 2+ , Cu 2+ , Pb 2+ , and Zn 2+ in the presence of cupferron as a chelating agent by square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV). The technique is based on the catalytic reduction of adsorbed cupferron-metal ion complexes at the surface of the ERGO-HgF-PGE at 0.1 V for 60 s in 0.1 M acetate buffer solution (pH 4.6). Owing to the improved electronic and surface effects associated with ERGO inclusion, improved sensitivity was further achieved. Under optimized conditions, the ERGO-HgF-PGE showed a linear relationship from 20 to 200 μ g.l −1 with detection limits below the US-EPA of 0.17 μ g.l −1 , 0.02 μ g.l −1 , 0.17 μ g.l −1 and 0.14 μ g.l −1 for Cd 2+ , Cu 2+ , Pb 2+ and Zn 2+ , respectively at a deposition time of 60 s. The ERGO-HgF-PGE exhibited highly reproducible results with negligible intermetallic interferences and applied successfully to the determination of trace metals in tap water with satisfactory results.