Development And Application Of Multi-pesticides Residue Analytical Methods In Earthworms

As a major organism in the soil ecosystem,earthworm can reflect the influence of pesticides on environmental organism.However,there is no convenient method to detect pesticide residues in earthworms at home and abroad,which makes it difficult for us to quickly identify the categories and sources of pollutants.Therefore,the construction of new and efficient pesticide residue analysis technology in earthworm samples is of great significance for us to carry out reasonable and effective monitoring and targeted remediation technology.Using the advantages of traditional QuEChERS?quick,easy,cheap,efficient,rugged and safe?and rapid separation of magnetic nanomaterials,a high-throughput multi-pesticides residue pretreatment analysis in earthworms can be established.This study is based on the magnetic Fe₃O₄-SiO₂ made,according to the characteristics of earthworm fatty and high protein.The QuEChERS method is optimized and combination with ultra high performance liquid chromatography-tandem mass spectrometry?UPLC-MS/MS?analysis,development and application of high-throughput multi-pesticides residue analysis in earthworm samples.After systematically analyzing and verifying the feasibility of the method,it was applied to the analysis of actual samples to investigate the bioaccumulation behavior of earthworms after exposure to contaminated soil.The main results are as follows:1.Fe₃O₄ magnetic nanomaterials were prepared by hydrothermal solvent method,and modified by silanization to obtain Fe₃O₄-SiO₂.From the view of morphology,structure and the magnetic force,the properties of Fe₃O₄-SiO₂ magnetic materials were analyzed by means of scanning electron microscopy,transmission electron microscopy,vibrating sample magnetometer,X-ray diffractometer and flourier transform infrared spectrometer.The particle size of modified Fe₃O₄-SiO₂ nanoparticles increases,and the superparamagnetism remains unchanged.It still has a characteristic peak of Fe₃O₄ crystal form,and the SiO₂ vibration peak appears in the infrared absorption spectrum,which demonstrated the silica layer was successfully modified on the surface of Fe₃O₄ nano-particles.2.A high-throughput multi-pesticides residue analysis method for the determination of earthworm samples was established by modified QuEChERS method with UPLC-MS/MS.The amount of the extraction of solvent acetonitrile,Fe₃O₄,ZrO₂ and PSA were optimized for simultaneous determination of 50 kinds of pesticides.The optimum conditions were:extraction solvent acetonitrile 6 mL,adsorbent dosage of Fe₃O₄ 30 mg,ZrO₂ 20 mg and PSA 30 mg.Method validation showed that these target pesticides were linear in the range of 2 to 200?g/L with the correlation coefficients larger than 0.9239.The limits of detection were 0.1 to 1.0?g/L,while the limits of the quantitation were 20?g/kg for all the analytes.The recoveries of target analytes was65.1%¹27%and the relative standard deviation was 0.1%to 14.8%at the four level spiked concentration except cyproconazole.The present developed method can save 30%time in the sample pretreatment procedure compared to the conventional QuEChERS.The developed method possesses the advantages of easy operation,high sensitivity,which is suitable for high-throughput multi-pesticides residue analysis in earthworm samples.3.This method is used to analyze the actual sample and further verify its applicability.The earthworms were exposed to the soil contaminated with bifentrazol and to investigate the bioaccumulation behavior of bifentrazol in earthworms.The results showed that during the enrichment process,the bioaccumulation factor for bioaccumulation equilibrium was 1.81,indicating that the accumulation ability of bifentrazol in earthworms was general;the elimination process comply with first-order kinetics equation,the fitted equation was y=8.1728e^-0.711x with the correlation coefficient of 0.9364.The half-time was 0.97 days and the depletion rate constant was0.711 day^-1,illustrating a quick degradation process of bitertanol in earthworm.This result also displayed the feasibility of the developed method.In conclusion,the high-throughput multi-pesticides residue analysis method based on magnetic dispersion solid phase extraction combined with UPLC-MS/MS was developed in this study.Regarding the pretreatment consumption time,the present method demonstrated superiority to the non-magnetic QuEChERS method,achieving the high-throughput analysis of multi-pesticides residue in earthworm.In a view point of application,it can provide a new rapid detection methodology to help us explore the transformation,bioaccumulation and dissipation of pesticides in the environmental ecosystem.