The Residual Behavior And Processing Factors Of Fluazinam-Abamectin SC In Citrus

Citrus has high nutritional effect and economic value,and is especially suitable for the utilization of whole fruit resources,which has derived a variety of processed products,such as canned,citrus juice,fruit wine,citrus jam,medicinal tangerine peel,etc.Further pomace remaining after processing also has rich nutrients,which can be processed into animal feed or soil fertilizer again.In addition,Pesticides play an important role in the sound development of the citrus industry,but the residues of pesticides in citrus is harmful to the quality and safety of processed products,and affect human health.Therefore,the detection of pesticide residues in citrus and processed products is of great significance for assessing the risk of human exposure to pesticides and human compliance with good manufacturing practices.In this experiment,based on the improved Qu ECh ERS pretreatment method,ultra-high performance liquid chromatography tandem mass spectromrtry（UPLC-MS/MS）was used to simultaneously determine the residues of abamectin and fluazinam in different citrus matrices.Newhall navel orange was used as experimental material,and test of the orange residue degradation was carried out in Beibei,Chongqing.The residual degradation dynamics of abamectin and fluazinam in citrus were studied under the conditions of 5 times and 3 times the highest recommended dosage.Clarify the degradation half-life of 550 g/L fluazinam-abamectin SC in citrus,and provide scientific basis and reference for the reasonable and safe use of the two pesticides in the citrus industry.In addition,sweet orange was also used as experimental material,and the degradation of the residue was carried out in the field in Jiangjin,Chongqing and Hongjiang,Hunan.Apply the pesticide in the field at 5 times the highest recommended dose,and send the fresh citrus fruit immediately to the processing workshop for processing（the processing method is exactly the same as the commercial processing conditions of citrus juice）.The residual degradation of abamectin and fluazinam during the processing of citrus juice was studied,and the processing factor data of each processed product was calculated.The processing process in this study is exactly the same as the commercial processing of citrus juice.The processing factors of each processing procedure of citrus juice obtained in the experiment have high reference value for actual production.This result can provide a data basis for the improvement of citrus juice processing technology and dietary exposure risk assessment,and at the same time provide a relevant scientific basis for the registration and use of the compound fungicide product.The main findings are as follows:（1）The samples were pre-treated with Qu ECh ERS and used UPLC-MS/MS to determine the residual analysis method of abamectin and fluazinam in different citrus matrices.The citrus matrix was extracted with 1%acetic acid acetonitrile,purified by ethylenediamine-N-propyl（PSA）,separated on an Agilent Ecipes Plus C₁₈ column,gradient elution was carried out with 0.1%formic acid water-methanol as the mobile phase,and multi-reactive ion monitoring mode（MRM）scanning,ion pair binding retention time qualitative,external standard method quantification.The results showed that the concentration of abamectin and fluazinam had a good linear relationship in the range of 0.0025 to 1.0 mg/L,and the correlation coefficient（R²）was greater than 0.99.The average recovery rate of abamectin in different citrus substrates is between 72.9%and 101.7%,and the relative standard deviation（RSD）is between 1.6%and 13.6%.The average recovery rate of fluazinam in different citrus matrices is between 68.6%and109.1%,and the RSD is between 0.4%and 16.8%.The minimum added concentration of the two pesticides,the limit of quantification（LOQ）,is 0.01 mg/kg.The accuracy,precision and sensitivity of the detection and analysis method can meet the requirements of pesticide residue quantitative analysis in the pesticide residue test guidelines in crops.（2）The residual degradation of 550 g/L fluazinam-abamectin SC on citrus under a field application environment was studied.The results showed that in the field test in Beibei district of Chongqing,abamectin and fluazinam were administered once at effective doses of 825 mg ai/kg and 1375 mg ai/kg,respectively,and their degradation dynamics on citrus were consistent with the first-order reaction kinetic model.The degradation half-life of abamectin is 12-15 days,and the degradation rate after 42 days of application is above 84%.The degradation half-life of fluazinam is 17 to 23 days,and the degradation rate after 42 days of application is more than 67%.The dosage of abamectin and fluazinam was positively correlated with its half-life.（3）Study on the residues of abamectin and fluazinam in various processed products during the commercial processing of citrus juice.The results showed that:Jiangjin District of Chongqing and Hongjiang of Hunan Province were used as the test sites,and 5 times the highest recommended dose（active ingredient:1375 mg ai/kg）was used as the spraying dose.The spraying was carried out twice with an interval of 7 day.After 28 days（safety interval）,fresh citrus samples were collected and processed immediately.In the commercial processing of citrus juice,washing and peeling can effectively remove part of the pesticide residues in citrus.In the entire processing process,except for the extraction of citrus peel essential oil,the remaining processing processes can effectively reduce the residual amount of abamectin and fluazinam in citrus and its processed products.Fortunately,the juice extraction process is the most effective process to reduce the residues of these two pesticides.The removal rate of fluazinam in citrus virgin juice after squeezing is 89.7%～95.5%,while the removal rate of abamectin is close to 100%.（4）Research on the processing factors of abamectin and fluazinam in various processed products during the processing of citrus juice.The results showed that the extraction of essential oils during the commercial processing of citrus juice significantly increased the residues of abamectin and fluazinam,in essential oil products,the residual processing factors of abamectin are 28.791～30.590,and the processing factors of fluazinam are 5.217～5.669.Except for citrus peel essential oil,the residual processing factors of abamectin and fluazinam in other processed products are all less than 1.