Residue Analysis And Digestion Dynamics Study Of 20% Dinotefuran-spirol Ethyl Ester Suspension On Citrus

This paper mainly introduced the residual detection of dinotefuran and its metabolites(UF/DN)and spirotetramat and its metabolites(SE/SM/SG/SK)in citrus peel,pulp,whole fruit and soil by liquid chromatography/tandem mass spectrometry(LC-MS/MS).The terminal residues and dissipation dynamics of 20% dinotefuran and spirotetramat suspension concentrate(SC)in citrus peel,pulp,whole orange and soil were investigated at Guizhou,Hunan and Guangxi in 2013 and 2014.The data could provide theoretical basis and technical support for the safe use and residual detection of dinotefuran and spirotetramat in citrus.Dinotefuran and its metabolites were extracted with methanol/water(v/v,1/1),and spirotetramat and its metabolites were extracted with acetonitrile(1% acetic acid),The mixtures were vortexed,ultrasonically extracted and centrifuged,then purified by dispersive solid phase extraction.The concentrations of dinotefuran and its metabolites,spirotetramat and its metabolites were determined by LC-MS/MS.Dinotefuran and spirotetramat were completely separated from impurities in 8 min and 15 min,respectively.The results showed that the matrix-matched standard curves of dinotefuran/UF/DN had good linearities in the range of 0.02-5.00 ?g/mL with the correlation coefficients(R)of 0.9928-0.9999.The limits of detection(LODs)and quantification(LOQs)were 1.56×10-12 g and 0.08 mg/kg,respectively.The spiked levels of dinotefuran,UF and DN ranged from 0.08 to 20 mg/kg.The average recoveries were between 80.86% and 105.85% with RSD of 0.63%–6.16% in soil and orange matrices(including peel,pulp and whole orange).The matrix-matched standard curves of spirotetramat/SE/SM/SG/SK showed good linearities in the range of 0.005-5.000 ?g/m L with R values of 0.9981-1.0000.The LODs and LOQs were 1.25×10-11 g and 0.02 mg/kg,respectively.The spiked levels of spirotetramat/SE/SM/SG/SK ranged from 0.02 to 20 mg/kg.The average recoveries were between 71.46% and 114.85% with RSD of 0.43%–12.32% in soil and orange matrices.The terminal residues and dissipation dynamics of dinotefuran and spirotetramat in citrus peel,pulp,whole orange and soil were investigaed at three trial fields in two years.The results demonstrated that when the applied dosage was at 100 mg a.i./kg,dinotefuran and spirotetramat dissipated fast,and the dissipation dynamics followed the first-order kinetic models in soil and whole orange.The half-lives of dinotefuran and spirotetramat were 6.8-19.8 and 5.7-6.5 days,respectively.The terminal residues of dinotefuran and spirotetramat were lower than 10 and 1 mg/kg in soil and orange matrices at Guizhou,Hunan and Guangxi in 2013 and 2014.Moreover,the dissipation behaviors(indoor)of dinotefuran and spirotetramat in soil were studied under different conditions.The results showed that the dissipation rates of dinotefuran and spirotetramat in soil had positive correlation relationships with microorganism,organic matter and water contents of soil.