| The residue analysis method, dynamics of digestion, the final residue and safety evaluation of the pesticide difenoconazole and propiconazole were studied in the agricultural products. These provide an important theoretical and scientific basis for the formulation of guidelines of the pesticide, product registration and maximum residue limits of difenoconazole and propiconazole in the tomato, banana and rice.Residue analysis method of difenoconazole and propiconazole was established in tomato,banana and rice. The tomato and banana sample was extracted with ethyl acetate, while the rice sample was extracted with acetonitrile. They all were determined by UPLC-MS/MS. The difenoconazole precursor ion/product ion transitions were m/z 406/251 and m/z 406/337 at the mode of multi-reaction monitor and m/z 406/251 was used for quantification; The propiconazole precursor ion/product ion transitions were m/z 342/159 and m/z 342/273 at the mode of multi-reaction monitor and m/z 342/159 was used for quantification. The limit of detection in UPLC-MS was 1×10-12 g for difenoconazole and propiconazole , and limits of quantitation were 0.005 mg/kg for all matrices. In the four levels of 0.01 mg/kg, 0.05 mg/kg, 0.1 mg/kg and 0.5 mg/kg the average recoveries were 75.0%～107.1% and 71.4%～104.6%, with the relative standard deviations of 2.1%～9.9% and 1.7%～10.8%, respectively. The sensitivity, accuracy and precision of the method well satisfied the essential rules of pesticide residue determination.The results of residual dynamics of difenoconazole and propiconazole in tomato, banana, rice and soil showed that: the half life of difenoconazole were 3.3～3.8 d in tomato, 4.4～6.5 d in soil. The half life of propiconazole were 6.9～10.9 d in banana, 23.9～29.4 d in soil. The half life of difenoconazole were 1.8～5.4 d in rice plant, 2.6～8.2 d in soil, and 2.2～6.1 d in water; The half life of propiconazole were 1.8～5.1 d in rice plant., 4.6～8.3 d in soil, and 2.3～6.7 d in water. the results of residual dynamies showed that difenoconazole and propiconazole disspated fast in tomato, banana and rice.And the degradation dynamics of difenoconazole and propiconazole accorded with the kinetic equation: C = Coek.When the tomato was treated for two times and three times, on the 3th day after the last application, the final residue of difenoconazole in tomato was between 0.115 mg/kg and 0.444 mg/kg. When the banana was treated for two times and three times, on the 40th day after the last application, the final residue of propiconazole in banana was between ND and 0.068 mg/kg. When the rice was treated for two times and three times, on the 21th day after the last application, the final residue of difenoconazole in rice plant was between 0.023 mg/kg and 0.068 mg/kg, in rice husk was between 0.090 mg/kg and 1.545 mg/kg, in brown rice was between ND and 0.096 mg/kg. The final residue of propiconazole in rice plant was between 0.042 mg/kg and 0.789 mg/kg, in rice husk was between 0.079 mg/kg and 0.992 mg/kg, in brown rice was between 0.006 mg/kg and 0.073 mg/kg. These showed that the final residue inereased as the applieation dosage and applieation times increased, or as the harvest interval decreased.The safety evaluation of the difenoconazole and propiconazole results suggested that difenoconazole 10% EC be used in tomato at most two times at a dose of 100 mL/mu with a safe interval of 7 days from harvest; the propiconazole 20% EC be used in banana at most two times at a dose of 400 time of fluids with a safe interval of 40 days from harvest; the difenoconazole·propiconazole 30% EC be used in rice at most two times at a dose of 20 g/mu with a safe interval of 21 days from harvest. The results of the final residue assay indicated that it made sure the safty of three different agricultural products, when the two fungicides difenoconazole and propiconazole were used in the recommended application dosage, application times and the harvest interval.
|
PDF Full Text Request