Electro-oxidation and determination of benomyl by square-wave adsorptive stripping voltammetry

The electro-oxidation of the benomyl fungicide was studied by square-wave adsorptive stripping voltammetry. The voltammetric current at a glassy carbon electrode was acquired within the pH range 1.0-10.0. The quantitation was performed using the peak generated at +1144 mV by scanning the potential from +0.00 to +1600 mV (versus an Ag/AgCI reference electrode, 3 M NaCl). Accumulation potential = 0.0 mV, accumulation time=45 s, frequency=75 Hz, pulse amplitude=-60 mV, and staircase step potential = 7 mV were used as square-wave parameters. The peak current versus concentrations plot were rectilinear over the range from 0.081 to 1.496 microg/mL with an LOD of 0.024 microg/mL. Mean recovery was 99.0% (0.198 +/- 0.011 microg/mL), which was very close to the benomyl content spiked into river water (0.20 microg/mL). The method was efficiently applied for benomyl determination in the pesticide formulation Minelate 50WG, and the average determined content of 49.8 +/- 0.16 (n = 5) was consistent with the 50% benomyl (w/w) quoted by the manufacturer. The benomyl voltammograms recorded between days exhibited a negligible degradation into carbendazim metabolite, and therefore all results were given as the total benomyl concentration. The high recoveries and low RSD gave evidence of good accuracy and precision.