| Pyridaben is da nang ketone insecticide. In China, it is mainly used for the control of citrus, apple, cotton, vegetables and other harmful mite pests. However, the residual dynamics and final residues of pyridaben in rice were not been reported both domestic and abroad.In this issue, a gas chromatography?GC? method was developed to determine the residues of pyridaben in rice matrix. The field trails were conducted at Guizhou, Guangxi and Heilongjiang province during the agricultural season in 2014 and 2015 to study the dynamic dissipation and terminal residue of pyridaben. A scientific basis for the safely use and residue determination of pyridaben in rice matrix was carried out. The paddy water was extracted with ethyl acetate; paddy soil, rice husk samples were extracted with acetonitrile; rice plant was extracted with acetonitrile, then the solution was cleaned up by Evni-Carb-Cartridges solid phase extraction column; brown rice was extracted with ethyl acetate. The residues of pyridaben was determined by GC-ECD. The results showed that the external standard curve expressed a good linearity between 0.05 and 10.0 ?g/m L with the correlation coefficient of 0.9999. The limit of detection was 1.60×10-11 g. The limit of quantification was 0.00125 mg/kg, 0.005 mg/kg, 0.020 mg/kg, 0.010 mg/kg and 0.020 mg/kg in paddy water, paddy soil, paddy plant, brown rice and rice husk, respectively. The spiked levels in the five matrixes of paddy water, paddy soil, paddy plant, brown rice and rice husk were different. The spiked levels of pyridaben were from 1.25×10-3 to 0.25 mg/kg in paddy water, from 4.64×10-2 to 6.0 mg/kg in paddy soil, from 0.20 to 25.0 mg/kg in paddy plant, from 0.01 to 0.50 mg/kg in brown rice, and from 0.02 to 5.0 mg/kg in rice husk, respectively. The recoveries were ranged from 77.59% to 108.7% with RSDs between 2.40% and 8.47%. The method was suitable for pyridaben determination in rice matrix.The residues of pyridaben in paddy water, paddy soil, rice plant, brown rice and rice husk were carried out. The results showed that the MRL of pyridaben was below 0.01 to 0.033 mg/kg at harvest time?the dosage was 120 g a.i/ha and was applied twice?, which was much lower than the MRLs of European Union?0.05 mg/kg?. Therefore, 40 % pymetrozine·pyridaben SC can be applied safely on rice with the recommended dosage and time.Moreover, in order to explore the environmental factors for the degradation of pyridaben in different soil, indoor simulation experiment was designed. A method of determining pyridaben in soil was developed by an ultra-performance liquid chromatography-photodiode array detection?UPLC?. The preliminary influence of different soil environmental factors on pyridaben residual degradation was obtained, which provide a reference for the degradation of pyridaben in the environment. |
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