Residual Analysis And Digestion Dynamics Of Chiral Pesticide Toxic Fluoride And Phosphorus On Watermelon

At present,approximately 40% of current-use pesticides have at least one or more than two chiral carbons,and most of the chiral pesticides are sold in the form of racemic forms on the market,in China.Under achiral conditions,their enantiobiological,toxicity and environmental selectivity are quite different.Therefore,the risk evaluations of chiral pesticides residue in food and the environmental matrix based on the data obtained by traditional achiral methods are often incomplete and nonspecific.Thus,it is of great significance to develop enantiomeric analysis methods of chiral pesticides and investigate the different environmental behavior of the single enantiomer to supply more accurate data for evaluating the environmental risk and food safety.Dufulin was developed by the Center for Research and Development of Fine Chemicals of Guizhou University.The residues and degradation of dufulin in watermelon field was studied in this thesis,in order to establish reasonable treatment strategy of dufulin on watermelon,and supply data support for environmental risk as well as dietary risk assessment.According to the physicochemical properties of Dufulin,an analytical method of ultra-high performance liquid chromatography with a superchiral S-OD chiral column coupled with high-resolution mass spectrometry was established for the determination of Dufulin residues after extracted from watermelon,pulp and soil samples.To optimize the pretreatment method for detecting rac-dufulin in the three matrixes,different extraction solvents,extractant volumes,extraction times,and absorbents were investigated to improve extraction efficiency.Moreover,analysis of variance was used to perform method validation for determination of the two dufulin enantiomers in the three matrixes.Using the optimized method,good linearity was obtained(determination coefficient>0.9991).The average recoveries of the two enantiomers in the three matrixes at four spiked levels ranged from 75.0 to 107.8%,with intra-and inter-day relative standard deviations of 0.4-10.4%.The accuracy and sensitivity of the method meet the requirements of pesticide residues analysis.The residual dynamics and final residues study of Dufulin in Guizhou and Beijing were simultaneous investigated between year 2016~2017,In field trials,the R enantiomer was preferentially dissipated in watermelon.But,no stereoselective degradation in soil was observed.