Square wave voltammetric determination of diquat using natural phosphate modified platinum electrode

A platinum electrode modified with natural phosphate (NP) was evaluated as an electrochemical sensor for diquat (DQ) in aqueous medium. The electrode was prepared by the deposition of natural phosphate on the platinum surface. Diquat was preconcentrated on the surface of the modified electrode by adsorbing with natural phosphate and reduced at a negative potential in 0.1 M K2SO4 solution. The influence of accumulation time and pH of the electrolytic solution were investigated. The calibration graph obtained under the optimized conditions was linear with a correlation coefficient of 0.9813 at levels near the detection limits up to at least 5.32 × 10−9 mol L−1 with the relative standard deviation (RSD) lower than 3.37%. Interferences by some metals were investigated. Fe, Zn, Cu, MnO4 and Hg apparently affected the peak currents P1 and P2 of diquat. The natural phosphate modified platinum electrode was applied to the determination of diquat in natural water samples. The results indicate that this electrode is sensitive and effective for the determination of diquat.