| There is growing concern regarding the safety and environmental impacts of pesticide adjuvants,which are key components of agrochemical formulations.Alkylphenol ethoxylates(APxEOs,where x is the number of ethoxylate units),including nonylphenol ethoxylates(NPxEOs)and octylphenol ethoxylates(OPxEOs),are one of the most frequently used non-ionic surfactants.Their metabolites,alkylphenols,are environmental hormone disruptors and have bioaccumulation potential,estrogenic activity,reproductive and developmental toxicity in biota.Because of the potential negative impacts of APxEOs and their metabolites on human and ecological health,the production and use of APxEOs have been banned or restricted by many countries in Europe and North American.Owing to the superior surface properties and low cost of APxEOs,they are still used as adjuvants in agrochemical formulations in China.The widespread application of such pesticides inevitably results in the transport of a portion of APxEOs and their degradation products to the environment and agro-products,which not only affect food safety,but also pose negative impacts on both the environment and consumers.Therefore,it is necessitated to develop analytical methods to measure APxEOs and their metabolites,investigate these compound residues and assess their associated dietary risks in agro-products and the environment.In addition,it is important to explore the the environmental fate of APxEOs following application as adjuvants along with the pesticides in the crop field.This thesis established analytical methods for the determination of NPxEOs,OPxEOs and their metabolites in agro-products and the environment.The residue distribution of these compounds in agro-products was investigated,and then their associated dietary risks were assessed.Besides,the dissipation pattern and residue distribution of NPxEOs in the cucumber-field system were also explored.The main contents and findings of this thesis are as follows:1.An analytical method based on selective pressurized liquid extraction(SPLE)and liquid chromatography-tandem mass spectrometry(LC-MS/MS)for the determination of 46 APxEOs(x=1–20),NP1EC,and APs in agro-products and soil was established.The theoretical calculation method was used to characterize the concentration distribution of NPxEOs or OPxEOs,which could provide a reference for quantitative analysis.The reported sample preparation techniques for APxEOs and their degradation products involve multi-step operations,and thus require more time,manpower,money and solvent consumption.The SPLE method was used as the sample preparation technique in this study because it integrates the extraction and cleanup in one step,reduces manual operations and meets the needs of high-throughput and automaticity to a great extent.The extraction solvent for SPLE as well as the types and amounts of sorbents in the PLE cell were optimized.The average recoveries at three(low,medium,and high)spiking levels were 67%–118%with relative standard deviations(RSDs)of1.1%–14%for the tested matrices.The limits of detection(LOD)and quantification(LOQ)were0.001–120μg/kg and 0.003–400μg/kg,respectively.Conclusively,the method can achieve automatic(on-line)clean-up,simplify the experimental process,reduce sources of blank contamination,and meet the requirements for the analysis of APxEOs and their degradation products in agro-products and the environment.2.A rapid and sensitive method based on modified quick,easy,cheap,effective,rugged,and safe“QuEChERS”method and supercritical fluid chromatography-tandem mass spectrometry(SFC-MS/MS)was developed for simultaneous determination of APxEOs(x=2–20)in vegetables.Under optimized conditions,the 38 target analytes were analyzed within 5 min.To the best of our knowledge,the run time of 5 min is the shortest that is required for the analysis of NPxEOs and OPxEOs.The linearities of the matrix-matched standard calibrations were satisfactory with coefficients of determination(R~2)>0.99and the limits of detection(LOD)and quantification(LOQ)were in between 0.02–0.27μg/kg and0.18–1.75μg/kg,respectively.The recovery of all target analytes spiked at three(low,medium,and high)fortification levels were ranged from 73%–123%with relative standard deviation(RSD)≤18%.The method was successfully applied to market samples.Thus,the newly developed method is rapid and versatile,and can serve as an effective and reliable technique for the analysis of APxEOs in vegetables.In addition,this method could be a reference for the rapid separation and analysis of other non-ionic surfactants.3.The residue characteristics of 46 APxEOs(x=1–20),NP1EC,and APs in the main production areas of peaches,cherries,and kiwi in China in 2016 and 2017 were investigated and analyzed.4-NP,4-NP2EO,NPxEOs(x=3–11)and OPxEOs(x=5–14)were detected in all samples.The total concentration of 46 analytes among peaches,cherries,and kiwifruit had significant differences,and there were also significant differences between 2016 and 2017.Only significant positive correlations between the total concentration of 46 analytes and total pesticide residues were found in peaches.It was speculated that pesticide application was not the only source of these analytes in these fruits.In addition,dietary exposure risk assessments were conducted based on the monitoring data of three fruits and it was found that the dietary intake risk of 4-NP,4-t-OP,and∑APxEOs was acceptable.4.Cucumber field trials were conducted to study the dissipation patterns and final residual distribution of NPxEOs in cucumber,leaves and soil,and the risk of dietary intake was assessed.The half-lives of NPxEOs in the three matrices were 3.1–6.9 d,which suggested that NPxEOs were easy to degrade,while 4-NP had longer half-lives of 5.6–11.9 d,which needs much attention.More spraying times and higher usage dose made higher final residues while the longer harvest interval resulted the lower residues.A dietary risk assessment of 4-NP and∑NPxEOs on cucumber suggested that the dietary intake risk was acceptable. |
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