Residue Dynamic Of Thifluzamid And Sulfoxaflor In Dendrobium Officinale And Residue Change During Processing

As the precious Chinese medicine,Dendrobium officinale contains a large number of beneficial medicinal active ingredients to human health,and has a wide application range in medicine,food and cosmetics beauty areas.With the applying of artificial cultivation,damage of diseases and pests in Dendrobium officinale increasingly serious,especially Sclerotium rolfsii and Aleyrodidae.Currently,there is no pesticide registered in Dendrobium officinale.In this study,thifluzamide and sulfoxaflor were selected as research pesticides and establish residue analytical met-hods of two pesticides in samples of Dendrobium officinale,dissipation rules and their final residues were also be explored.Meanwhile,the behavior of these two pesticides during Dendrobium officinale processing were also studied.The results of study could provide scientific basis in control quality of Dendrobium officinale.The main results as follows.1.Analytical methods for determination thifluzamide and sulfoxaflor in samples of Dendrobium officinale were developed.Thifluzamide in Dendrobium officinale stems,leaves,dry samples and cultivate substrate were extracted with acetonitrile,liquid-liquid partition by dichloromethane,clean-up using graphitized carbon black and determined by GC-ECD;sulfoxaflor were extracted with acetone,liquid-liquid partition by n-hexane and dichloromethane,clean-up using neutral Al2O3 solid phase extraction(SPE)and determined by HPLC-UVD.Thifluzamide and sulfoxaflor in Dendrobium officinale juice were extracted by liquid-liquid partition using dichloromethane.Results showed that the average recoveries of thifluzamide in different samples ranged from 76.6%to 102.7%with RSDs from 2.1%to 9.2%and average recoveries of sulfoxaflor ranged from 78.5%to 96.3%with RSDs from 3.5%to 9.8%.2.The degradation dynamics and final residues of thifluzamide and sulfoxaflor were studied in field experiments.Results showed that the degradation dynamics of these two pesticides accord with the first kinetic equation in Dendrobium officinale stems,leaves and cultivate substrate,the half-live of thifluzamide and sulfoxaflor were 25.56 d,15.33 d,23.79 d and 8.31 d,8.96 d,7.67 d respectively.The maximum residue of thifluzamide in fresh stems and dry samples of Dendrobium officinale were 1.25 mg/kg and 4.73 mg/kg respectively when the havest interval was 60 d,and the maximum residue of sulfoxaflor were 0.95 mg/kg and 2.60 mg/kg respectively when the havest interval was 28 d.3.The behavior of thifluzamide and sulfoxaflor in Dendrobium officinale processing were investigated.After three different drying methods,the PFs of these two pesticides all showed that microwave-drying<sun-drying<oven-drying.After oven-drying,these two pesticide residues were increased more because of the losing of moisture with the PFs of thifluzamide and sulfoxaflor from 2.06 to 4.02 and 1.26 to 2.06 respectively,and these two pesticide residues were decreased with the increasing of temperature and time of oven-drying.After juicing process,residues of thifluzamide and sulfoxaflor were 0.074 and 0.033 mg/kg respectively in Dendrobium officinale juice.Meanwhile,washing and peeling process reduced the amount of residues by more than 70%.The effects of different solution on the remove of these two pesticide residues in Dendrobium officinale were different,extending washing time and adding a small amount of NaCl into washing solution can efficiently remove thifluzamide and sulfoxaflor residues.