Study On Residue Behaviors Of Two Dufulin Products In Tobacco

Dufulin was a new type of anti-plant virus agent,which was widely used to prevent and control viral diseases and can reduce the occurrence of other diseases in crops,improve the quality of crops,and has a certain yield increase effect.However,there have been no reports comparing the residual behavior of different dufulin formulations.In order to provide scientific basis for the safe use of dufulin,the residue behavior of dufulin wettable powder and suspension concentrate on tobacco was studied.The main results were as follows:The QuEChERS extraction and purification methods were established for dufulin,the sample was extracted by a mixed solution of acetonitrile and water(acetonitrile:water,v/v,5:1),purified by carbon nanotubes and finally detected by LC-MS/MS.The standard curve r2in fresh tobacco leaves and flue-cured tobacco substrates were from 0.9999 and 1.000,and the linear range was from 0.01 to 1 mg/L,the recoveries of the fresh tobacco leaves were between 84%and 117%,relative standard deviations(RSDs)were between 3%and 5%,the recoveries of the flue-cured tobacco leaves were between 80%and 119%,RSDs were between 2%and 5%,and the limit of quantitation(LOQ)was 0.05 mg/kg.This method can quickly and efficiently detect the dufulin content in fresh tobacco leaves and flue-cured tobacco leaves.To study the residual dissipation dynamics of two products of dufulin on tobacco,in 1year,field trials of two dufulin products on tobacco will carried out in 8 fields.The results of field trials reveal that the half-life of 20%dufulin suspension concentrate in fresh tobacco leaves and flue-cured tobacco leaves were from 6.8 d to 13.0 d and 11.2 d to 19.1d,and the r~2 were from 0.803 to 0.966 and 0.957 to 0.979;The results of field trials reveal that the half-life of 30%dufulin wettable powder in fresh tobacco leaves and flue-cured tobacco leaves were from 3.9 d to 10.3 d and 0.1 d to 1.4 d,and the r~2 were from 0.829 to 0.994 and0.650 to 0.769;Except for Guizhou,the degradation rate of 30%dufulin wettable powder is faster than that of 20%dufulin suspension concentrate.The residual test results showed that the residual amount of the two formulations of dufulin did not exceed 20 mg/kg after 28 days of the last application.Therefore,the recommended safety interval after application on tobacco is 28 days.The 20%dufulin suspension concentrate was sprayed with 300 g a.i./ha(formulation was100 g/mu)before the onset of tobacco virus disease or after initial dilution with water.The amount of water per mu 50 kg.The interval was 7 days;The 30%dufulin wettable powder was sprayed with 495 g a.i./ha(formulation was 110 g/mu)before the onset of tobacco virus disease or after initial dilution with water,and the amount of water per mu was 50 kg.The interval of 2 times application was 7 days.Combining residue data from field trials and food intake levels,the dietary intake risk of dufulin in tobacco is assessed.From the results,the average daily intake of dufulin in the general population was 1.474 mg,accounting for 4.3%of the daily allowable intake.The results showed when 20%dufulin suspension concentrate and 30%dufulin wettable powder were harvested 28 days after the last application according to the recommended application method,the dufulin residues in tobacco will not cause unacceptable harm to public health.