Research On Multi-residue Analysis Method Of Organophosphorus Pesticides Based On Molecular Imprinting And Metal-organic Framework

Organophosphorus pesticides are widely used in agricultural pests and diseases due to their high efficiency,broad spectrum,and multiple modes of action.However,their high toxicity has caused great public concern.Therefore,it is particularly necessary to develop efficient and highly sensitive rapid detection methods.Here are established molecular labeling-surface-enhanced Raman spectroscopy（MIP-SERS）and metal organic framework magnetic solid phase extraction-liquid chromatography tandem mass spectrometry（MSPE-HPLC-MS/MS）methods for the determination of multi-residue organophosphorus pesticides.It can provide rapid and confirmatory detection methods for multi-residue detection of organophosphorus pesticides in agricultural products and environmental samples.1.Using sodium citrate reduction method to prepare gold nanosol as the SERS enhanced substrate,a surface-enhanced Raman spectroscopy method was established for simultaneous detection of phosemet,fenthion and triazophos.The experiment optimized the conditions of gold nano sol substrate,type and concentration of coagulant,p H value,and reaction time.The three pesticides（phosemet,fenthion,and triazophos）have distinct characteristic peaks at 604 cm^-1,1222 cm^-1,and 1408 cm^-1,respectively,and the peak height and concentration at this characteristic peak Shows a good linear relationship,and the correlation coefficients are all higher than 0.9865.In this experiment,organophosphorus pesticides with different signal characteristic peaks were screened,and the detection parameters and conditions were explored,which laid the foundation for the rapid detection of organophosphorus pesticides in the matrix.2.Using fenthion as the template molecule,methacrylic acid as the functional monomer,and ethylene glycol dimethacrylate as the crosslinking agent,molecularly imprinted polymers（MIPs）of organophosphorus pesticides were successfully prepared by precipitation polymerization.The adsorption experiments show that the synthesized MIPs have good selective adsorption performance.Optimized the type of accelerator,concentration of accelerator,p H value and reaction time and other conditions.Under the optimal conditions（1 mol/L KCl,p H value of 7,and reaction time of 10 s）,a method based on MIP-SERS for the determination of organophosphorus pesticide residues in agricultural products（peaches and pears）was established.The SERS peak heights and concentrations of the three organophosphorus pesticides（phosemet,fenthion,and triazophos）showed a good linear relationship,the correlation coefficients were all higher than 0.9844,and the detection limit was 0.02～0.05 mg/L.The standard recovery rate is73.9%～98.2%,which provides an important reference for the application of SERS technology in actual agricultural products.3.The magnetic metal-organic framework composite（Fe₃O₄/ZIF-8）was prepared by in-situ polymerization,and a high performance liquid chromatography tandem mass spectrometry method for magnetic solid phase extraction of organophosphorus pesticides was established.A variety of characterization methods were used to verify the morphology,structure and performance of the material.ZIF-8 has a polyhedron with uniform particle size（150～200 nm）,Fe₃O₄nanoparticles are attached to the surface of ZIF-8,and the composite material exhibits good magnetic response and fast and efficient enrichment performance.With Fe₃O₄/ZIF-8 as the solid phase extraction adsorbent,combined with high performance liquid chromatography tandem mass spectrometry,the magnetic solid phase extraction conditions（the amount of adsorbent,extraction time,p H value,elution solvent and sample volume）were optimized.Under the optimal conditions,the 6 organophosphorus pesticides showed good linearity in the range of 1～200 ng/mL（R²>0.9963）,the detection limit was 0.08～1.2 ng/mL,and the recovery rate of standard addition was 72.0%～99.6%（10 ng/mL,20 ng/mL,50 ng/mL）.This method can provide confirmation technology for the detection of organophosphorus pesticides.