Determination of trace arsenic(III) by differential-pulse anodic stripping voltammetry with in-situ plated bismuth-film electrode

Abstract

A sensitive and precise method is presented for the determination of As(III) by differential-pulse anodic stripping voltammery (DPASV). This method is based on the co-deposition of As(III) with Bi(III) onto a basal-plane type of pyrolytic graphite substrate at an accumulation step. DPASV studies indicate that the As was oxidized with anodic scans to give an enhanced anodic peak at about 500 mV vs. Ag/AgCl. Addition of L-cysteine to test solutions was found to be highly effective to obtain reproducible oxidation responses due to As(0) → As(III). A linear relationship between the anodic stripping peak-current ratio (I As/I Bi) and As(III) concentration was observed over the concentration range from 0.0200 µg L−1 to 18.0 µg L−1. The detection limit of As(III) was 0.012 µg L−1 at a deposition time of 180 s. The relative standard deviation was 2.85% (n = 8) at a concentration of 10.0 µg L−1 As(III). Analytical results demonstrate that the determination of As(III) in real water samples is possible by the proposed method.