Degradation dynamics of organophosphorus insecticides applied in stored soybean (Glycine max L.) during supervised trials.

During storage, soybean kernels can be attacked by insects, which are preventively controlled with insecticides. Information on the dissipation of insecticide residues is crucial to know their final concentrations in food and establish waiting periods necessary for consumption without health risks, determine minimum period comply national international standards. The aims this study were quantify residue levels organophosphorus insecticides (dichlorvos, chlorpyrifos-methyl pirimiphos-methyl) stored soybean, effect during storage period, model dynamics. Insecticide soybeans analyzed at 2, 30, 60, 90 120 days after application. An analytical method based QuEChERS extraction followed gas chromatography mass spectrometry (GC-MS/MS) determination was validated, mean recoveries 82-105%, depending spiking levels. Residues decreased below 80% initial concentration 60 application quantifiable days. a pseudo-first-order dynamics [Ct = C0×exp(-k.t)], constant (k) half-lives being 0.538 1.3 dichlorvos, 0.018 38.8 chlorpyrifos-methyl, 0.023 30.1 pirimiphos-methyl, respectively. These results allow concluding that, recommended dosage, these safe use grains under standard conditions commonly nowadays used Argentina.