Development of a portable method for monitoring and speciation of arsenic in aquatic systems by anodic stripping voltammetry: Applications to real samples

The aim of this study was to develop a differential pulse anodic stripping voltammetry (DPASV) method for the rapid, sensitive and cost-effective determination and speciation of inorganic arsenic in aquatic environments. The electrochemical determination of arsenite and arsenate was investigated using a rotating solid gold electrode (SGE). As(III) was selectively determined at +0.1 V by ASV after a deposition at -0.3 V. The total As content (As(V) + As(III)) was electrochemically reduced at -1.2 V by nascent hydrogen to As⁰, and then As(V) was evaluated indirectly by subtraction. Electrochemical reduction of As(V), instead of chemical reduction, was chosen to minimize the consumption of chemical reagents, reduce analysis time and provide a method suitable for on-site analysis. First, the operating parameters were optimized, and the method was characterized in terms of selectivity, sensitivity, linearity, precision and accuracy. A Limit of Detection (LOD) of 0.10 μg L^-1 was found for the developed technique for As_(tot). The method was then applied to the direct quantitative determination and speciation of inorganic arsenic in real water samples; the results obtained showed satisfactory agreement with those produced by the hydride generation technique coupled with inductively coupled plasma atomic emission spectroscopy (HG-ICP-OES). Subsequently, the voltammetric determination of arsenic was explored with a portable potentiostat to evaluate the reliability of the procedure for on-site detection.