Residue Dissipation And Dietary Risk Assessment Of Flonicamid In Potato

China is the country which has the largest potato growing area and production in the world.Potato is the fourth largest main crop in China besides maize,rice and wheat.Aphids are one of the main pests in potatoes.Aphids feed on the young parts of potato leaves,leading to the yield reduction by prohibiting the potato growing.Aphids are also the vectors of potato virus disease.Potato virus disease can be transmitted to the next generation through seed potatoes,thus reducing the yield and quality year after year,causing more significant damage.Chemical control is the main means to control potato aphids.At present,the commonly-used insecticides for control aphids mainly are pyrethroid and neonicotinoid insecticides.These two types of insecticides have two problems: one is the problem of drug resistance.the other is the problem of the killing of beneficial insects.Comparing with traditional pyrethroid and neonicotinoid insecticides,flonicamid serves as a better choices in terms of solving these two problems.Flonicamid is less toxic to humans,bees,fish,birds,predators,and silkworms.Moreover,it has no cross-resistance with pyrethroids and neonicotinoids.The technical material of flonicamid passed registration protection period on March 24,2017.As a result,the use of flonicamid will increase significantly in China.In order to adapt to the international and domestic situation.In this study,we conducted field experiments at two sites with an interval of two years.From the research on flonicamid residue methods,digestion rules,final residue and risk assessment,the safety application of flonicamid in potato was proposed and the following results were achieved:1.A multi-residue detection method for determination of flonicamid and its metabolites TFNA(4-trifluoromethylnicotinic acid)and TFNG [N-(4-trifluoromethylnicotinoyl)glycine],thiamethoxam and its metabolite clothianidin in potato plants,tubers,and soil was established.Flonicamid,thiamethoxam and metabolites were extracted with acetonitrile containing 1% acetic acid,then cleaned up by d-SPE(dispersive solid phase extraction)method.The separation of compounds was carried out by reversed-phase C18 column,and eluted with 0.1% acetic acid water-methanol as mobile phase at a flow rate of 0.3 mL/min.Detection of analytes was performed by high performance liquid chromatography tandem mass spectrometry(HPLC-MS/MS)using multiple reactive ion detection mode(MRM)and external standard quantitation.The average recovery of the flonicamid,thiamethoxam and metabolites was between 73.7% and 106.3%,the RSD was between 0.8% and 16.5%.The LOQs of all chemicals were 0.05 mg/kg which met the standard of pesticide residue analysis.2.The dissipation of flonicamid is consistent with first-order kinetics.The half-life in potato plants is between 0.23 and 2.05 d,and the half-life of flonicamid in soil ranged from 0.02 to 2.22 d.At the harvest stage,only TFNG was detected in potato tubers,and the final residual concentration was between 0.054 and 0.126 mg/kg.Flonicamid and its metabolites TFNA and TFNG were not detected in the soil.3.For the dietary risk assessment of flonicamid in potato,the risk quotient is 0.0063,which is far less than 1.for the dietary risk assessment of flonicamid in registered crop for china,the risk probability is 23.8%,which is less than 100%,indicating that the resulting risk is acceptable.