Tolfenpyrad In Tea Analysis Method, Residue Level And Safety Evaluation Research During Processing

As a pyrazole heterocycles insecticide,the tolfenpyrad has good control effect on tea leafhoppers,and because of its high efficiency,fast degradation and good function of contact killing,it has become an important substitute for insecticides.In this paper,an analysis method has been established for determination of tolfenpyrad in fresh tea,green tea,tea infusion and spent tea leaves by optimization of the sample detection conditions and pretreatment methods.By using this method,the fresh tea samples were detected under different dosages;the influence of green tea processing on the content of tolfenpyrad were analyzed;the effects of different infusion treatments on the transter rate and remained rate of tolfenpyrad were investigated;under the condition of producing the maximum transfer rate of tolfenpyrad,the dynamic green tea samples under three dosages were infusion to evaluate the safety of this insecticide based on the safety quantitative evaluation system.The research results are as follows:1?An analysis method has been established for determination of tolfenpyrad in tea matrices by optimization of the sample detection conditions and pretreatment methods.The evaluation and validation results of the method shown that excellent linear relationships are observed for tolfenpyrad in acetonitrile,fresh tea,green tea,tea infusion and spent tea leaves,with all the correlation coefficientsn?R²?values being more than 0.9953 at the concentrations of 0.075-15?g/m L.The limit of quantification?LOQ?and limit of detection?LOD?are in the range of 0.0007-0.0063 mg/kg and 0.0002-0.0019 mg/kg,respectively,and the matrix effect?ME?between-68.5%and 4.6%were obtained.The recovery rates avhieved from spiked tea samples ranged from 75.1%to 104.6%with relative standard deviations of?RSDs?of 3.2%-13.6%.It revealed that the proposed method can meet the basic requirements for pesticide residue analysis.2?Based on the developed method,the fresh tea samples at three dosages in filed trials were detected.The results revealed that the dissipation dynamics of tolfenpyrad in fresh tea samples which has a regularity and keeping with the first-order kinetic equations.And the rate of digestion was highest at 21 days after application this insecticide.When the application dosage are 67.5,90.0 and 112.5 g a.i/ha,the first-order kinetic equation of tolfenpyrad in fresh tea samples are C=5.8397e^-0.078t?R²=0.9211?,C=8.9767e^-0.084t?R²=0.9096?and C=14.132e^-0.074t?R²=0.9430?,respectively,with half-life of 8.9,8.3and 9.4 d.3?The tolfenpyrad residues in fresh tea dynamic samples at three application doses were 1.04-13.8 mg/kg.The residual contents in the green tea were 2.59-13.68mg/kg by the traditional green tea processing,and the processing factors are in the range of 0.64-2.77.Compared to most of the fresh tea samples,the pesticide residues in processed tea showed an increasing trend.4?The green tea samples containing tolfenpyrad residues were infusion through the change of external factors including water temperature,infusing time,influsing times and the ratio of tea and water.The result revealed that in the condition of boiling water,inflused for 10 min,first inflused and the ratio of tea and water at 1:30,the tolfenpyrad can be maximum infusion and minimum remained.5?The green tea samples were infusion at three dosages by using the established preparation method of tea infusion.The results revealed that the residue of tolfenpyrad in tea infusion and spent tea leaf were 0.39-4.61 mg/L and 1.53-9.44mg/kg,respectively,with infusion factor of 0.09-0.57.In addition,the remained rate of tolfenpyrad in spent tea leaves at the range of 34.5%-85.3%.According to the maxmimun transfer rate at three dosages,the tolfenpyrad was absorbed into the humen's body by drinking between 0.232 and 0.548?g/kg bw.It can be summarized that the numbers are less than the pesticide's ADI value of tolfenpyrad,and it is safety to use.