Enhanced Cathodic Preconcentration of As(0) at Au and Pt Electrodes for Anodic Stripping Voltammetry Analysis of As(III) and As(V)

• Published in: Journal of physical chemistry. C Vol. 119; no. 21; pp. 11400 - 11409
• Main Authors: Bu, Lijuan, Gu, Tiean, Ma, Yixuan, Chen, Chao, Tan, Yueming, Xie, Qingji, Yao, Shouzhuo
• Format: Journal Article
• Language: English
• Published: American Chemical Society 28.05.2015
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.5b01435

We report that the cathodic preconcentration of electron-insulating As(0) on Au and Pt electrodes can be enhanced by chemical reduction of As­(III) and As­(V) by electrogenerated H2, as studied by cyclic voltammetry. This finding is used for sensitive anodic stripping voltammetry (ASV) analysis of As­(III) and/or As­(V) at the Au electrode. About three As(0) monolayers were cathodically preconcentrated on the Pt electrode at −0.3 V (vs SCE) in 0.5 M aqueous H2SO4, as a result of both the chemical reduction of the solution-state As­(III) near the electrode surface by the electrogenerated H2 and the direct electroreduction of As­(III) on the highly catalytic surface Pt sites. Only one As(0) monolayer was electrodeposited at −0.2 V (vs SCE) on the Au electrode in 0.5 M aqueous H2SO4, but about two As(0) monolayers were deposited on the Au electrode at a more negative potential at which the mild evolution of H2 occurred. The electrogenerated H2 could also chemically reduce As­(V), though the direct electroreduction of As­(V) was sluggish on the Au electrode. Linear sweep ASV (LSASV) oxidation of the preconcentrated As(0) to As­(III) and then to As­(V) at a fast scan rate gave two sharper and higher anodic peaks on the Au electrode than on the Pt electrode. On the basis of these observations, sensitive dual-signal LSASV analysis of As­(III) and/or As­(V) was achieved on the Au electrode, with limits of detection of 1.0 nM for As­(III) and 5.4 nM for As­(V) under optimized experimental conditions. Our method was successfully applied for analysis of As­(III) and/or As­(V) in real water samples. The insights into cathodic As(0) deposition provided here may help the better understanding of electrochemical deposition of many other electron-insulating thin films, especially those obeying the electrode material-dependent inner-sphere mechanism, for electrochemical and surface-coating applications.