| Ginseng is a perennial herb of the family Araliaceae and a kind of precious traditional Chinese medicine in China,whose roots,stems,leaves and fruits can be used as medicine.With the increasing demand for ginseng,it was listed in the category of new resource food by the Ministry of Health of China in August 2012.During the cultivation of ginseng,it is seriously affected by pests and diseases,and the pesticide control is the main prevention and control measure.However,due to the irrational use of a large number of pesticides and the long cultivation period of ginseng,pesticides are more likely to accumulate in plants,which leads to excessive pesticide residues in ginseng,which seriously affects the quality of ginseng and poses a safety hazard to human health.Fluopyram is a pyridylethyl benzamide fungicide,which plays an effective role in the prevention and control of grey mould,downy mildew,phytophthora cactorum,sclerotinose and powdery mildew on more than 70 kinds of crops such as pear,stone fruit,vegetable and field crops.Trifloxystrobin is a methoxyacrylates fungicide,which has good prevention and control effects on fungal diseases such as grey mould,downy mildew,anthracnose and rust.The combination of fluopyram and trifloxystrobin has been developed as a new complex fungicide in recent years,which has low toxicity,high efficiency and broad-spectrum bactericidal effects.It can not only prevent disease and protect the health of crops,but also balance growth and development to improve the quality of agricultural products,but it has not yet been registered on ginseng.In this study,a multi-residue detection method for simultaneous determination of fluopyram and its metabolites BZM?2-?Trifluoromethyl?benzamide?as well as trifloxystrobin and its metabolite CGA 321113 in ginseng was established.At the same time,it also provides reliable technical support and reasonable scientific basis for the formulation of MRL values of fluopyram and trifloxystrobin and the safety use and evaluation of them on ginseng.The main research results are summarized as follows:1. A multi-residue detection method for simultaneous determination of fluopyram and its metabolites BZM?2-?Trifluoromethyl?benzamide?as well as trifloxystrobin and its metabolite CGA 321113 in ginseng plants,soil,fresh and dried ginsengs was established.The residues of analytes in ginseng plants,soil,fresh and dried ginsengs were extracted with acetonitrile and purified by Qu ECh ERS method.Finally,the residues were detected by HPLC-MS/MS under multiple reaction monitoring mode?MRM?and quantified by external standard method.The results showed that a good linearity was abtained in the concentration range of 0.001-1.0 mg/L for fluopyram and its metabolites BZM as well as trifloxystrobin and its metabolite CGA 321113,and the correlation coefficient?r?were>0.9980.The mean recoveries of analytes at three spiked levels of 0.01?0.05 and 0.1 mg/kg in ginseng plants,soil,fresh and dried ginsengs ranged from 73.3 to 100.6%,with the relative standard deviation?RSD?of0.4-17.6%.The limit of quantitation?LOQ?was 0.01 mg/kg.The results showed that the sensitivity,accuracy and precision of this method are good,and all meet the requirements of pesticide residue analysis.2. The field trails containing degradation dynamic and terminal residue experiment were conducted in four experimental sites including Fusong,Yanji,Jingyu,Huanren in2018.The results showed that the half-lives of fluopyram in ginseng plants and soil samples were 6.5?9.8 d and 9.1?11.4 d,respectively,and those of trifloxystrobin in ginseng plants and soil samples were 4.7?12.2 d and 4.2?8.7 d,respectively,which indicated that they were easily degradable pesticides in ginseng plants and soil.The terminal residues of fluopyram in plant,fresh ginseng and dried ginseng samples were0.206?48.961 mg/kg,<0.01?0.092 mg/kg and<0.01?0.305 mg/kg,respectively,and those of trifloxystrobin in plant,fresh ginseng and dried ginseng samples were0.220?53.841 mg/kg,<0.01?0.086 mg/kg and<0.01?0.264 mg/kg,respectively.It is recommended to use 43%?500 g/L?suspension concentrate containing fluopyram and trifloxystrobin to control ginseng gray mold,spraying the stems and leaves in the early stage of the disease at the dosage of 450 m L/ha?225 g ai/ha?,which can be applied up to 2 times,with an interval of 7-10 days and a safety interval of 7 days.3. Based on the terminal residue data on ginseng,the acute and chronic dietary risks of fluopyram and trifloxystrobin in ginseng were evaluated.The results showed that the acute dietary risk values of fluopyram in fresh and dried ginseng were2.63×10-5and 8.71×10-5,respectively,and the chronic dietary risk values were 43.64%and43.69%,respectively.The ARf D?Acute Reference Dose?of trifloxystrobin has not been formulated,which indicates that the acute dietary risk of trifloxystrobin is acceptable,and the chronic dietary risk value of trifloxystrobin in fresh and dried ginseng was 8.12%.The risk quotients were all less than 100%,which indicates that the acute and chronic dietary intake risks of fluopyram and trifloxystrobin on ginseng are acceptable. |
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