Analysis of imidacloprid and penconazole residues during their pre-harvest intervals in the greenhouse cucumbers by HPLC-DAD

The purpose of this research is to investigate the residues of imidacloprid and penconazole in cucumbers, since pesticides have been highly demanded in the production of greenhouse crops. According to Codex Alimentarius Commission statement, the maximum residue limits (MRLs) for imidacloprid and penconazole in cucumber are 1 and 0.06 mg kg(-1), respectively. To have samples under control, cucumbers were planted in a greenhouse. The treatments were applied in a factorial test with a completely random statistical design. Each treatment (blank, penconazole, imidacloprid, and the mixture of penconazole and imidacloprid) has been replicated four times. The liquid chromatography with diode-array detector (HPLC-DAD) was used to quantify residues of the selected pesticides. The statistical analysis showed that time has a significant difference on pesticides residues. Moreover, imidacloprid had a faster degradation than penconazole in cucumber fruits due to the high photolysis of imidacloprid in aqueous solutions. The results also demonstrated that penconazole residue was decreasing linearly during the time (R-2 > 0.91), while imidacloprid followed a power function in time (R-2 > 0.94). Consequently, the cucumber fruits, which are treated with imidacloprid, could be harvested after first day of spraying due its shorter indoor half-life than penconazole.