Establishment Of 3 Chiral Pesticides Detection Methods In Pu'er Tea And Preliminary Study On Microbial Degradation Of Dinotefuran

Objective:Pu'er tea is a unique famous tea in Xishuangbanna,Lincang,Dali,Pu'er,Maguan and other places in Yunnan Province.Drinking tea has become one of people's favorite drinks,at present,and the quality and safety of tea has also attracted people's attention.Dinotefuran is the third generation of neonicotinoid pesticide with a wide range of action,strong insecticidal activity,and good application prospects.This paper studies the residues of three chiral pesticides in Pu'er tea,such as dinotefuran,Isocarbophos and indoxacarb in Pu'er tea and the degradation of dinotefuran in the fermentation process of Pu'er tea,which provided theoretical basis for further studies on the degradation and metabolism of dinotefuran.Methods:The method was established with acetonitrile of 1%acetic acid as extraction agent,PSA and carb as purification materials,Chiralpak IG chiral column for separation,ultra performance liquid chromatography tandem mass spectrometry for determination,and external standard method for quantification.Through the fermentation of sun-dried green tea,we found that there were strains that degraded dinotefuran and the degradation and metabolism of dinotefuran under natural conditions and sunlight,and the production of metabolites UF and DN.Results:The three chiral pesticides have good linearity at 0.002?0.2mg/L,the correlation coefficient(r)is greater than 0.993,and the limit of quantification is 0.0025?0.25 mg/kg.The average recoveries of the three addition levels of 0.025,0.05,and 0.5 mg/kg in Pu'er tea and sun-dried tea were 87.6%-123.67%,and the relative standard deviations were 2.6%-18.7%.Two strains,Aspergillus niger,Aspergillus fumigatus and Aspergillus niger,were isolated from the ferm entation process of Pu'er tea,which could degrade dinotefuran.The half lives of dinotefuran degradation by Aspergillus fumigatus at 25? and 37? is 18.0d a nd 7.0 days,the half lives of Aspergillus niger to degrade dinotefuran at 25?and 37? is 18.9d and 13.3d.The effect of Aspergillus niger at 25?,the enantiomer of dinotefuran may have enantiomeric conversion,from R-(-)-dinotefu ran to S-(+)-dinotefuran.Studies was found that the enantiomers of dinotefuran were not transformed when it was degraded in sunlight or natural state,but there were metabolites DN and UF.Conclusion:A method for the determination of chiral pesticides of three insect icides in Pu'er tea was established.Two strains were selected from the ferment ed Pu'er tea to promote the degradation of dinotefuran.This article comprehens ively analyzes the degradation and metabolism of dinotefuran in tea.