The application of a mode of double preconcentration and double stripping steps in combination with a flow system to decrease the detection limit and increase the selectivity of determinations in stripping analysis of As(III)

Due to the fact that arsenic has very harmful and toxic effects on living organisms monitoring of its content in various environmental samples at trace level concentrations is desirable and highly recommended. Such advantages as low cost and portable instrumentation, achieving low detection limits and most of all the possibility of the direct determination of As(III) with no separation step make stripping voltammetry suitable for the determination of arsenic.  

These data concer the application of double deposition and double stripping steps mode in combination with a flow system for anodic stripping voltammetric determination of As(III) ions. An advantage of the proposed way of the voltammetric measurements is a decrease of the detection limit as compared to the values obtained using a traditional three-electrode system thanks to an initial preconcentration of the analyte on the first working electrode as well as the significant increase in a selectivity of As(III) determination thanks to the possibility of solution exchange after the first deposition step.

The proposed way of the voltammetric measurements leads to the following analytical advantages: (i) a decrease of the detection limit as compared to the values obtained using traditional three-electrode system by an initial preconcentration of the analyte using the large-surface area electrode; (ii) an increase of the selectivity of voltammetric determinations thanks to the application of a flow system and exchange the solution after the first deposition step; (iii) simplification of performing the measurements in comparison to the original version of double accumulation and stripping steps mode due to the lack of a need to change the position of the first working electrode; (iv) the possibility of analysis of samples with a complex matrix thanks to the use of a flow system leading to minimization of matrix effects in the second deposition step. The developed procedure of As(III) determination offers a wide linear dynamic range in the range from 1 × 10-9 to 5 × 10-8 mol L-1 at a deposition time of 120 s at both working electrodes. The detection limit for As(III) determination was 4.8 × 10-10 mol L-1. The undoubted advantage of the described procedure is its high selectivity. The tolerable limit of excess of Cu(II), which is the main interferent in the course of anodic stripping voltammetric As(III) determination, was significantly increased thanks to the solution exchange after the first deposition step. The correctness of the proposed procedure was confirmed by analysis of a real water sample and lake water certified reference material by obtaining satisfactory recovery values. The additional advantage of the proposed procedure is a miniaturization of the measurement system and the use of environmentally friendly electrodes.