Residual Analysis And Digestion Dynamics Of Chiral Pesticide Toxic Fluorine And Phosphorus In Cucumber And Soil

Dufulin is a new type of chiral antiviral agent which was developed by Center for Research and Development of Fine Chemicals,it was widely used in cucumber,tomato and other vegetables to prevent and cure the virus disease because of its high efficiency and low toxicity.At present,most of researches on the analysis of dufulin enantiomers were based on the normal phase liquid chromatography(LC)and no study was reported on the analysis of dufulin enantiomers in reverse phase LC system.This paper aims to establish an reverse phase liquid chromatography with tandem mass spectrometry(LC-MS/MS)method to detect the residues of dufulin enantiomers in cucumber and soil samples.And based on the method,the terminal residues and dissipation dynamics of 20%dufulin suspension concentrate(SC)in cucumber an soil were investigated at Anhui,Beijing and Guizhou in 2016 and 2017,which might provide theoretical basis and technical support for the residual analysis of dufulin enantiomers in other crops.Dufulin enantiomers were extracted by acetonitrile as the extractant,then the extracts were purified by dispersive solid-phase extraction method.The enantiomers wereseparatedonaSuperchiralS-ODchiralcellulose tris(3,5-dimethylphenylcarbamate)column at 20°C,with a mixture of acetonitrile and water(0.1%formic acid)as mobile phase at a flow rate of 0.65 mL/min.The pretreatment conditions were optimized using an orthogonal test,and the optimized method showed good linearity and sensitivity.The results showed that the matrix-matched standard curves of dufulin enantiomers also had good linearities in the range of 0.01-4.00?g/mL with the correlation coefficients(R~2)>0.9986.The limits of detection of the instrument were 2.0×10~-1111 g,the limits of quantification were0.02 mg/kg.The spiked levels of R/S enantiomers were both 0.02,0.2,2 and 8 mg/kg in soil,the average recoveries were 80.97-96.21%and 82.75-95.44%,respectively.And the relative standard deviations(RSDs)were 3.10-4.43%and 1.30-4.89%,respectively.The spiked levels of R/S enantiomers were both 0.02,0.2 and 2 mg/kg in cucumber,the average recoveries were 91.92-98.42%and 86.54-97.57%,respectively.And the RSDs were 1.61-4.99%and 5.61-9.72%,respectively.The method was successfully applied to determine dufulin in real cucumber and soil samples.The results demonstrated that R-dufulin degraded faster than S-dufulin in the cucumber samples of Anhui and Beijing,and in the soil samples of Anhui.The residues of S-dufulin were 0.03-0.28 mg/kg,0.05-0.48 mg/kg and 1.21-5.41 mg/kg,and the residues of R-dufulin were 0.09-0.46 mg/kg,0.03-0.37 mg/kg and 1.05-5.42mg/kg in soil at Anhui,Beijing and Guiyang,respectively.The residues of S-dufulin were<0.02-0.17 mg/kg,0.02-0.22 mg/kg and 0.02-0.35 mg/kg,and the residues of R-dufulin were<0.02-0.14 mg/kg,0.02-0.15 mg/kg and<0.02-0.32 mg/kg in cucumber at Anhui,Beijing and Guiyang,respectively.The residues of enantiomers in soil were higher than that in cucumber,and the residues of enantiomers in soil at Guiyang were higher than that in soil at Anhui and Beijing.