Development Of Pesticide Multi-residue Pretreatment Method Based On Fe₃O₄ Nanoparticles

Fe₃O₄nanoparticles,a noval nanomaterial,have the characteristics of large specific surface area,multiple adsorption sites and high adsorption specificity,which provide a new purification strategy for the pretreatment of pesticide residues analysis.In this study,Based on Fe₃O₄nanoparticles,a method to detect 30 representative pesticide residues in eight vegetable（lettuce,cucumber,carrot,tomato,pepper,shallot,chinese flowering cabbage,and cabbage）was established.This method used single Fe₃O₄nanoparticles as the matrix solid-phase dispersion extraction purification materials,acetonitrile as the solvent elution and UHPLC-MS/MS for pesticide residue detection means.Various condition parameters,such as types of elution solvent,volume of elution solvent,and amounts of FNPs,were optimized.Meanwhile,recoveries,limit of quantitation、linear equation、relative standard deviation and matrix effect were also validated.The sample and Fe₃O₄nanoparticles were fully ground and transferred into the column.The mixture was eluted by acetonitrile for several times.The eluent was then collected and evaporated under rotation,after that the solution was subjected to ultrasound.Method validation results show that for most pesticides and matrixs,the average recovery is good,which were 70-110% with relative standard deviations lower than 13.5%.But,the recovery of prothiazole in some matrixs was not higher than 48.8%.Excellent linearity（R²≥0.9832）was achieved at concentration levels of 0.01–1 mg/L,and the limits of quantification29 pesticides could reach 0.01 mg/kg while dinotefuran was 0.1 mg/kg,based on the spiked test.Recoveries of all pesticides were also compared when Fe₃O₄nanoparticles and traditional adsorbent PSA were used respectively.The recoveries of 30 pesticides were all higher than 72.1%（72.1-101.9%）with relative standard deviations in the range of 1.4%-11.8%.The developed method was successfully applied to nanning vegetable samples（lettuce,cucumber,carrot,tomato,pepper,shallot,chinese flowering cabbage,cabbage,et al）.Although part of the pesticide residues were detected in eight kinds of vegetables,most of the detected contaminants did not exceed the maximum residue limit（MRL）set by the European Commission,with exceeding standard rate not more than 6%.In this research,it was proved that the pesticide multi-residues detection method based on Fe₃O₄nanoparticles,has good accuracy and high precision,which meets the needs of pesticide residue analysis and can be used for the detection of real vegetable samples.Meanwhile,Fe₃O₄nanoparticles can be used as a substitute for clean up materials such as PSA for pesticide residue analysis.