Antimony (Sb) is ubiquitously present mainly as Sb(III) and Sb(V) in the environment as a result of natural processes and human activities. LC-MS and HG-AFS are commonly used in the analysis of Sb content and speciation. However, their high prices and immobility characteristics limit the spread of these methods. Due to the unique capability of pre-concentrating analytes at/in the working electrode surface, electrochemical stripping analysis has been recognized as one of the most convenient choices for measuring trace metal ions. But except for the determination on its total concentration, the speciation determination of Sb(III) and Sb(V) by electrochemical analysis has not yet been realized in the same solution without adding any oxidizer/reductant or using complex mathematical calculations, which is mainly because of the significant difference between the electrochemical activities of Sb (III) and Sb (V) and the difficulty in separating the electrochemical signals of Sb(III) and Sb(V).

The theoretical research related to photooxidation characteristic of Sb(III) is widely studied in recent years, but this feature is not well used yet. This research, based on the photooxidation characteristic of Sb(III) and the electrochemical activity difference between Sb(III) and Sb(V), realized the determination of Sb species in one electrolyte solution by anodic stripping square wave voltammetry (AS-SWV) without adding any enthetic oxygenant. The electrolyte solution used in this research was 2.0mol/L HCl. Under this condition, Sb(III) had an obvious anodic stripping peak at the enrichment potential of -0.4V. While an obvious stripping peak of Sb(V) was observed under a more negative enrichment potential of -0.9V. Therefore, the interference of Sb(V) on Sb(III) determination can be avoided under the enrichment potential of -0.4V. After the determination of Sb(III), the whole system was exposed to ultraviolet light for a suitable time to make sure all Sb(III) was oxidized to Sb(V). Then Sb(V) was detected under the enrichment potential of -0.9V, which represented the total Sb concentration (Sb(tot)) in solution. The original Sb(V) concentration was calculated by difference subtraction method with the results of Sb(tot) and Sb(III). The linear range of Sb(III) and Sb(tot) were 0.6 to 1.5μmol/L and 0.8 to 10.0μmol/L, with the detection limits of 4.21nmol/L and 5.05nmol/L, respectively. This method had been successfully applied to Sb speciation and concentration determination in lake water and seawater samples.