Study On Difenoconazole Residue In Apples And Soil

Due to the characteristics of difenoconazole, such as high efficiency, long duration,broad spectrum, it was used commonly on apple production. The difenoconazole residuesin apple directly influence the fruit quality and export, so apple food security and soilecological security in orchard should be explicit after the difenoconazole was sprayed. Thestudy explored the detection method of difenoconazole, and determined the difenoconazoleresidue in growing apple and orchard soil, storage apples, marketing apple by the method,which provided a theoretical basis for apple edible safety and rational drug use in appleproduction The results of this study were as follows:1．Difenoconazole detection methods, which was a set of acetonitrile extraction, theflorisil column purification, n-hexane:acetone (v:v=6:4) elution, Gas Chromato-graphy-electric capture detector detection to analyze difenoconazole residues in apple andsoil, were improved on the basis of NY/T761-2008. The minimum detectableconcentration and quantity were0.01mg/kg and0.02ng in apple and soil. The averagerecovery of difenoconazole was80.1%~102.5%, and the relative standard deviation was4.0%~17.5%in apple. The average recovery was82.3%~94.1%, and the relative standarddeviation was2.8%~13.4%in the soil. All of that meet the standards of pesticide residueanalysis.2The residual dynamics and final residues of difenoconazole in apple and soil weredetected in2011and2012. The results showed that the half-life of difenoconazole innon-bagged fruits was12.83days in2011and15.54days in2012, while in soil was37.27days and40.07days respectively; the half-life of difenoconazole was31.94days in baggedfruits in2012. In2011and2012, it was for7days after the bagged apples and non-baggedapples were all spayed2and3times with100and66.7mg/L difenoconazole10%WG thatthe residue of difenoconazole in the harvested fruit was all lower than Maximum ResidueLimit0.5mg/kg and in bagged fruits was lower than0.03mg/kg; the residue ofdifenoconazole of each treatment which had been analyzed was also lower than MRL0.5mg/kg after spraying for3days in2012. It demonstrated that difenoconazole was safe inapple production if following the recommended dose. It was concluded that bagging wasone of effective cultivation method to reduce the residue of difenoconazole. 3The relationship of between difenoconazole residue level and soaking concentration,storage temperature, storage time was studied after apples were soaked, the results showedthat the difenoconazole residues was positively correlated with fungicide soakingconcentration，but negatively correlated to storage time and temperature. The degradationrate had no obvious correlation with fungicide concentration, but it was positively relatedwith the storage temperature and negatively related with the storage time. The degradationrate was high at the early storage time and low in the late time, which was accord withfirst-order kinetics equation. With the consideration of food safety and storage effect, werecommend that difenoconazole soaking concentration was33.3mg/L or66.7mg/L, andstorage safety interval period for the treatment of66.7mg/L stored in4℃was35days.4The difenoconazole residue in apples collected from Baoding market includingseveral major apple-producing areas were surveyed. Nineteen samples were tested, theresidual samples accounted for42.11%, among that Fuji samples accounted for87.5%,while the residues were less than0.5mg/kg.