Determination of antimony(III) and (V) in natural water by cathodic stripping voltammetry with in-situ plated bismuth film electrode

A method is described for the sequential determination of Sb(III) and Sb(V) using Osteryoung square wave cathodic stripping voltammetry. It employs an in-situ plated bismuth-film on an edge-plane graphite substrate as the working electrode. Selective electro-deposition of Sb(III)/Sb(V) is accomplished by applying a potential of −500 mV vs. Ag/AgCl, followed by reduction to stibine at a more negative potential in the stripping step. Stripping was carried out by applying a square wave waveform between −500 and −1400 mV to the antimony deposited. The stripping peak current at −1150 mV is directly proportional to the concentration of Sb( III)/Sb(V). The calibration plots for Sb (III) were linear up to 12.0 µg L−1 depending on the time of deposition. The calibration plots for Sb (V) were linear up to 7.0 µg L−1, also depending on the time of deposition. The relative standard deviation in the determination of 0.1 µg L−1 of Sb(III) is 4.0% (n = 5), and the limit of detection is as low as 2 ng L−1. In case of 0.1 µg L−1 Sb(V), the relative standard deviation is 3.0% (n = 5) and the detection limit also is 2 ng L−1. The method was applied to the analysis of river and sea water samples.