Simultaneous Determination And Residue Degeradation Behavior Of Fenoxanil And Kresoxim-methyl In Paddy Field

Rice blast is one of the main diseases which often occurs and be serious harm to the yield and quality of rice in rice production process, the fungicides is mainly Fenoxanil and related agents and mixtures which is used for rice blast control,In order to accurately evaluate the ecological environmental behavior of Fenoxanil and Kresoxim-methylthe after Kresoxim-methyl-Fenoxanil26%suspension agent be used on rice, and guiding the science reasonable application of Kresoxim-methyl Fenoxanil26%suspending agent on rice. With indoor add recovery rate experiment and gas chromatography analysis of technology, researching and establishing the analysis and detection technology of Fenoxanil and Kresoxim-methyl residues in paddy rice samples.Later, through field test, after the Kresoxim-methyl-Fenoxanil26%suspending agent were used in paddy field, systematically analyzes the degradation situation of the effective components of Fenoxanil and Kresoxim-methyl in paddy field water, soil and rice plant and the residue situation in the paddy soil, straw, chaff and brown rice. The main conclusions are as follows:(1) Research and establish GC-ECD analysis method of Fenoxanil and Kresoxim-methyl residues in the paddy rice samples. The paddy water samples are directly extracted with dichloromethane; paddy soil, rice plant, brown rice, rice straw and chaff samples with acetone and water mixture as extraction agent, after being extracted with dichloromethane and purificated with Florisil column, then determined by GC-ECD.In the selected chromatographic conditions, Fenoxanil and Kresoxim-methyl standard working curve linear relationship is fine, the minimum detectable amount was1×10-11g, the minimum detectable concentration in paddy field sample respectively:water is0.01mg/L, paddy soil, rice plant, straw, chaff and brown rice were0.01mg/kg. the retention time of Kresoxim-methyl is about in12.7min, Fenoxanil is about in13.2min.When the concentration is0.05,0.50,1.00mg/kg, the addition recovery rate of Fenoxanil and Kresoxim-methyl was76.9%～120.5%in paddy water, soil, rice straw, chaff, rice plant and brown rice, and the average recovery was83.6%-106.7%, the relative standard deviation was2.1%～13.0%. The result is in the allowed range of the pesticide residue test criterion, which shows that the selected methods is in line with the technical requirements of the analysis and detection of pesticide residues.(2) In2010and2011, Kresoxim-methyl Fenoxanil26%suspending agent was evenly spraied after being diluted with water according to2025.0g/ha in paddy field in Hunan Changsha, Zhejiang Hangzhou and Guangxi Nanning three test points. The digestion process of the effective components of Kresoxim-methyl and Fenoxanil in paddy fields were consistent with the level of chemical reaction dynamics equation: Ct=Coe-kt, the elimination half-life of Fenoxanil in rice field water was5.39d-7.04d, in paddy soil was7.85d-9.83d, in rice plants was5.31d～6.90d; the elimination half-life of Kresoxim-methyl in rice plant was5.29d-6.26d. the degradation rate of Kresoxim-methyl and Fenoxanil after the application of14d was more than46%in rice plant, rice field soil and water, the digestion rate was more than89.66%in35d. These results show that Kresoxim-methyl and Fenoxanil were fast digestion in paddy field, and they are relatively easy degradable pesticides.(3) In2010and2011, Kresoxim-methyl·Fenoxanil26%suspending agent was evenly spraied after being diluted respectively with water according to1350.0g/ha and2025.0g/ha in paddy field in Hunan Changsha, Zhejiang Hangzhou and Guangxi Nanning three test points, The pesticide should be used3and4times, and the interval time should be7days, when the last application was done at14days before harvesting, the residues of the rice Kresoxim-methyl were less than0.05mg/kg; when the last application was done at21days before harvesting, Fenoxanil in brown rice residues were less than0.50mg/kg.(4) According to the recommended MRL and the experimental results, we propose the reasonably use suggestion of the Kresoxim-methyl-Fenoxanil26%suspending agent on rice are as follows:kresoxim-methyl fenoxanil26%suspending agent according to1350g/ha (commercial preparations, effective components for351.0a.i.g/ha, Fenoxanil is270.0a.i.g/ha, Kresoxim-methyl is81.0a.i.g/ha) is added with water diluted evenly spraying on rice, and controlling rice sheath blight and rice false smut, the pesticide should be most used3times, the interval time should be7days, the rice harvest safe interval period is21days.