Studies On Residual Degradation Of Diflubenzuron In Chinese Kale And Dietary Risk Assessment

Pesticides’ residue dynamic research is the basis of guide the scientific using pesticide and defining maximum residue limit.Diflubenzuron is a broad-spectrum and highly effective benzoylurea insecticide with contact and stomach toxicity.It was applied in rice,vegetables,fruit and other crops to control pest of Coleoptera,Diptera and Lepidoptera,such as armyworm,prodenia litura,beet armyworm,cabbage caterpillar and phyllocnistis citrella.It is safe for non-target organisms such as bees,frogs,and fish at the recommended dosage.In this paper,an analytical method for the determination of diflubenzuron residues in Chinese kale and soil via high performance liquid chromatography(HPLC)was established.After a year and six field trials,it was confirmed that 25%of the diflubenzuron WP the dynamic digestion process in Chinese kale and soil,and the final residue was calculated.The dietary risk of diflubenzuron on Chinese kale was evaluated.The aim is to provide a scientific basis for the rational use of diflubenzuron and the maximum allowable residue.The main research results are as follows:1.A HPLC coupled Eclipse Plus C18 column residue analysis method for diflubenzuron in Chinese kale and soil was established.Optimizing the flow ratio,flow rate,column temperature and other factors to achieve the separation of diflubenzuron and impurities,and the peak shape is symmetrical,the retention time is appropriate,and the resolution meets the requirements of residue analysis and detection.In the range of 0.1-60 mg/L,the concentration of diflubenzuron was linear with the peak area of the chromatogram,R2=1.Using acetonitrile and water as extraction solvents,Florisil silica column purification,the limit of quantitive concentration(LOQ)of diflubenzuron in Chinese kale and soil was 0.05mg/kg;the average recovery was 86.4%～102.2%,The relative standard deviation is 0.2%～8.1%,its sensitivity and accuracy meet the pesticide residue detection requirements.2.We studied the dynamic digestion process of diflubenzuron in Jiangsu and Jilin province soils and Chinese kale.There are considerable differences in the digestibility of diflubenzuron in the above two sites,and the result of applying the residual digestion system of diflubenzuron in the soil and Chinese kale shows that the decomposition is consistent with the basic rate formula.The half-life of diflubenzuron in Chinese Kale in Jiangsu and Jilin province was 2.8 d and 7.9 d,and the half-life of the soil was 8.2 d and 11.9 d,respectively.3.The final residual characteristics of a 25%diflubenzuron wettable powder in the Chinese kale and soil of Jilin Province,Hebei Province,Henan Province,Jiangsu Province,Hunan Province and Guizhou Province were investigated.And three times with a gap of 5-7 days.The residual amount of diflubenzuron of Chinese kale was 1.46 to 9.15 mg/kg,0.80 to 4.55 mg/kg and 0.43 to 0.96 mg/kg in the last application of 3.5 and 7 days.At the last application of 3,5,7 d,the residual amount of diflubenzuron in soil was<0.05 to 1.41 mg/kg<0.05 to 0.55 mg/kg<0.05 mg/kg.4.We assessed the dietary risks of diflubenzuron in Chinese kale.The risk probability was 63.7%,with diflubenzuron having a maximum dose of 244 g/ha and a safety time of 7 days.There is no health risk to the public and there is an acceptable level of risk.