Voltammetric behaviour of some nitropesticides at the mercury drop electrode

Classical DC-polarography and fast scan differential pulse voltammetry (FSDPV) were applied to study the reduction mechanism of five nitropesticides (trifluralin, benfluralin, pendimethalin, bromofenoxim, fluoroglycofen-ethyl) at a dropping mercury electrode (DME) and at a static mercury drop electrode (SMDE) in a medium of 47-49% (v/v) alcohol or 10-20% (v/v) dimethylformamide. The nitro groups were reduced to hydroxylamine derivatives or further to the corresponding amines depending on the type of compound and of solution acidity. The determination of nitropesticides was performed using FSDPV and adsorptive stripping voltammetry (AdSV) in model samples. The relative standard deviations were smaller than 4.5% for concentrations higher than 2 ng/ml. The detection limits were found both experimentally and calculated from regression analyses. According to the experimental conditions their values were in the range 17-160 ng/ml or 0.1-2.8 ng/ml for FSDPV or AdSV, respectively. The nitropesticides in artificially contaminated soils were determined after two to three times extraction with acetone. The recovery was about 96%.