Anodic Stripping Voltammetry of Arsenic(III) in the Presence of Copper(II) at a Mechanical Pencil Lead Electrode as a Screening Tool in Environmental Water

We have developed a novel, simple method for screening arsenic(III) by anodic stripping voltammetry on a commercial pencil lead as a working electrode. A potential of – 0.8 V vs. Ag/AgCl (3 M NaCl) was applied to pencil lead (thickness B and 0.9 mm diameter) in an aqueous solution of 5 mg/L copper(II) and 1 M nitric acid for 10 min under a nitrogen circumstance, followed by sweeping potential from – 0.8 to 0.8 V at 0.05 V/s. An anodic wave due to the oxidation of copper(0) with a peak potential at 0.13 V was obtained. In the presence of arsenic(III) with 5 mg/L copper(II) in the solution, the anodic peak potential shifted to more positive potentials, and the electric charge of the anodic wave increased. With the anodic wave charge above 0.15 V, a calibration curve in the range of 5.0 – 100 μg/L arsenic(III) with a relation coefficient of 0.990 was obtained. The relative standard deviation at 50 μg/L arsenic(III) was 4.8% (n = 5), and the lower detection limit was 1.6 μg/L (3σ). The present method was applied to river and lake water, and arsenic(III) added to the water was successfully recovered. A practical advantage of mechanical pencil lead as a working electrode involves that they are disposable after each measurement without any polishing, since pencil lead is inexpensive in spite of its high quality. The present method will thus probably serve as a rapid method for screening arsenic(III) in environmental water samples.