| Mefentrifluconazole is a new isopropanol triazole fungicide developed by BASF,which belongs to the sterol demethylase inhibitors（DMI）.Due to its own unique isopropanol group,it is highly effective against many resistant strains and can be used to control many diseases caused by fungi,such as leaf spot,rust,brown spot,black spot and early blight on cereals.However,the dissipation pattern and residues of mefentrifluconazole agents on crops after use have not yet been clarified.Potato is one of the most widely grown food crops in the world and is designated as the fourth largest staple food in China.Potato is susceptible to many pathogens during cultivation,which seriously endangers the normal growth of the crop and leads to a significant decrease in yield and quality,putting pressure on farmers’livelihoods and the economy of the potato industry.To prevent and control diseases,the use of fungicides has become one of the most important ways for farmers to protect their crops and agricultural products.However,due to the lack of basic knowledge about pesticides among farmers,farmers blindly and abusively use pesticides from time to time,resulting in pesticide residues in potatoes exceeding the national targets,which is harmful to the quality and safety of potatoes,the surrounding ecological safety and the health of consumers can not be underestimated.Therefore,in this paper,In this paper,in order to investigate the pesticide residues of mefentrifluconazole during the growth of potato,we established an analytical method for mefentrifluconazole residues in potato and soil;conducted field trials to determine the residues of mefentrifluconazole in actual samples and assessed the dietary risk.The main results of the study are as follows:1.A high performance liquid chromatography-tandem mass spectrometry（HPLC-MS/MS）method combined with improved Qu ECh ERS was developed for the residue analysis of mefentrifluconazole in potato tubers,potato plants and soil.The results showed that the average recoveries of mefentrifluconazole in potato tubers（0.01,0.05,0.5 mg/kg）,potato plants（0.01,0.05,0.5 and 5.0 mg/kg）and soil（0.01,0.05,0.5 and 5.0 mg/kg）at different spiked levels ranged from 73.4%to 105.3%with the relative standard deviations（RSDs）ranging from 1.6%to 11.8%;The minimum limits of detection were 3.1×10-5,2.5×10-5 and 2.7×10-5 ng for mefentrifluconazole in potato tubers,potato plants and soil,respectively;the limits of quantification were 0.01 mg/kg.It can be applied to the determination of mefentrifluconazole residues in potato.2.The disintegration dynamics of 240 g/L mefentrifluconazole·pyraclostrobin EC in potato tubers,potato plants and soil were tested in three locations in Changchun City of Jilin Province,Chifeng City of Inner Mongolia Autonomous Region and Hailun City of Heilongjiang Province.The results showed that the disintegration dynamics of mefentrifluconazole in potato tubers,plants and soil were in accordance with the first-order kinetic equation,with the half-lives ranged from 7.1 to 15.3 d,3.8 to 10.3 d and 10.5 to 21.2 d.The half-lives of mefentrifluconazole in potato tubers,plants and soil were less than 30 d,and it is a readily degradable pesticide.3.240 g/L mefentrifluconazole·pyraclostrobin EC in potato tubers,potato plants and soil were tested at three locations in Changchun City of Jilin Province,Chifeng City of Inner Mongolia Autonomous Region and Hailun City of Heilongjiang Province in 2021.The results of the field trials showed that Potato tubers,plants and soil samples were applied at low dose 198 g a.i./ha and high dose 297 g a.i./ha at the beginning of the disease,with 3 and 4 applications of each dose,and then samples were collected at 7,14 and 21 d after the last application,and residues of mefentrifluconazole in potato tubers were below 0.01 to 0.046 mg/kg.The residues in potato plants ranged from 0.281 to 4.834 mg/kg and in soil from 0.064 to 0.644 mg/kg.At present,the MRL of mefentrifluconazole in potato has not been developed in China,so according to the results of residue test in this paper,the MRL of mefentrifluconazole in potato is recommended in China.Therefore,based on the results of the residue test,the MRL of mefentrifluconazole in potato is recommended to be 0.05 mg/kg.4.Storage stability study of mefentrifluconazole in potato tuber samples were conducted.The residues of mefentrifluconazole in potato tuber samples stored under-20℃freezing condition were monitored over time,and there was no significant change in the residues of mefentrifluconazole in potato tuber during 180 d storage period,and its degradation rate was 0.4%to 11.4%,which indicated that mefentrifluconazole could be stored stably in potato tuber for 180d under-20℃freezing condition.5.The dietary risk of mefentrifluconazole in potato tuber was evaluated based on the final residue test data of potato tuber and the dietary structure of our population.The results showed that the long-term dietary exposure risk of mefentrifluconazole in potato tuber was 26.6%and the short-term exposure risk was 0.8×10-2%to 2.4×10-2%,which were less than 1,the results indicated that the dietary exposure risk of mefentrifluconazole in potato tuber was low and the health hazard index for consumers is small.Therefore,240 g/L mefentrifluconazole·pyraclostrobin EC was recommended for the control of early blight of potato with stem and leaf application,and the recommended application system dose was 825m L/ha（198 g a.i./ha）with three applications and a safety interval of 14 d.The potatoes were safe for human consumption by the time of harvest collection. |
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