Flow injection analysis of an ultratrace amount of arsenite using a Prussian blue-modified screen-printed electrode

We report here a new electrochemical method for the selective detection of ultratrace amount of arsenite (AsO2-, As3+) using a Prussian blue-modified screen-printed electrode (designated as PBSPE) by flow injection analysis (FIA) in 0.1 M, pH 4 KCl/HCl carrier solution. The Prussian yellow/Prussian blue redox couple of the PBSPE was found to mediate the As3+ oxidation. Various factors influencing the determination of As3+ were thoroughly investigated in this study. Under the optimized FIA conditions, a linear calibration plot in the range of 50 nM-300 muM with a detection limit (S/N = 3) of 25 nM (i.e., 64.9 pg in 20-muL loop) was observed at an operation potential of +0.6 V vs Ag/AgCl. The sensitivity was good enough to detect arsenite at levels lower than the current EPA standard. This modified electrode showed good resistance to interference from common ions, especially Cl-, which is generally considered as a major interference in the determination of As3+ by ICPMS. The practical utility of the PBSPE to detect As3+ was demonstrated in blackfoot disease endemic village groundwater from the southwestern coast area of Taiwan (Pei-Men).