Highly sensitive and selective anodic stripping voltammetric procedure of As(III) determination following double...

Double deposition and double stripping steps mode was used for the first time in combination with a flow system for anodic stripping voltammetric determination of As(III) ions. The proposed way of the voltammetric measurements leads to 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 of the selectivity of As(III) determination thanks to the application of a flow system. Optimization of the analytical procedure was performed. The calibration curve of As(III) determination was a straight line in the range from 1 × 10^-9 to 5 × 10^-8 mol L^-1. The estimated detection limit was 4.8 × 10^-10 mol L^-1 (deposition time of 120 s at both working electrodes). The repeatability of the proposed procedure calculated as RSD% for As(III) at a concentration of 1 × 10^-8 mol L^-1 was 3.8 % (n = 7). The tolerable limit of Cu(II) excess 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.