| Organophosphorus pesticides are a class of phosphate or thiophosphoric acid compounds,which have the effect of inhibiting acetylcholinesterase and have unique advantages in the prevention and control of pests and diseases,and are widely used in agricultural production.However,due to the irrational use of organophosphorus pesticides,their residues in agricultural products cause serious harm to public health.Therefore,it is important practical significance to establish efficient,sensitive and accurate method for the enrichment and detection of organophosphorus pesticides.Molecularly imprinted polymers have the advantages of structural predetermination,chemical stability and specific recognition,but have the disadvantages of slow mass transfer rate and low adsorption capacity.Metal-organic framework and flower-like molybdenum disulfide have large specific surface area and high stability,they lack specific recognition ability.In order to solve the shortcomings of the above materials and realize the efficient detection of organophosphorus pesticides,this paper using surface molecular imprinting technology,metal-organic framework@molecular imprinting hybrid composites and molybdenum disulfide@molecular imprinting hybrid composites were prepared to solve the shortcomings of the above single functional materials and realize the enrichment and detection of multiple organophosphorus pesticides in agricultural products.The main research results of this study are as follows:(1)The metal-organic framework@molecularly imprinted hybrid composites(ZIF-8@MIPs)were successfully prepared by surface molecular imprinting technique.The hybrid materials were characterized by scanning electron microscopy,transmission electron microscopy and Fourier-transform infrared spectroscopy,and the adsorption and recognition performance of the hybrid materials for organophosphorus pesticides(fenthion)were investigated by dynamic and static adsorption experiments.The results showed that ZIF-8@MIPs presented a typically core-shell structure with molecularly imprinted polymers shell(about 50 nm)homogeneously polymerized on the surface of metal-organic frameworks,and exhibited rapid and specific recognition ability towards organophosphorus pesticides.Under the optimal adsorption and desorption conditions(ACN-H2O as sample loading solvent,p H at 7,2 m L H2O for washing,3 m L 1%FA-ACN for eluenting),the established SPE-HPLC-MS/MS method based on ZIF-8@MIPs hybrid materials for the determination of organophosphorus pesticides in different agricultural products.The method showed good linearity(R~2?0.9927)in the range of 1?200?g/L.The recoveries of cauliflower,radish,pear and muskmelon were 82.5%?123.0%,with the relative standard deviation was lower than 8.24%.The established method had the advantages of high sensitivity,good selectivity and simple operation.(2)Flower-like molybdenum disulfide(Mo S2)was prepared by hydrothermal method,and the core-shell structure flower-like molybdenum disulfide@molecularly imprinted hybrid composites(Mo S2@MIPs)was successfully synthesized by polymerizing the molecularly imprinted polymers shell.Scanning electron microscopy,transmission electron microscopy and Fourier-transform infrared spectroscopy were used to characterize the hybrid materials,and the adsorption and specific recognition performance of the hybrid materials were investigated by dynamic and static adsorption experiments.The results showed that the molecularly imprinted polymers shell(about 50 nm)was homogeneously polymerized on the surface of flower-like molybdenum disulfide(about500 nm in diameter),and the hybrid material showed good specific recognition performance.Mo S2@MIPs was used as a solid-phase extraction adsorbent to identify and enrich organophosphorus pesticides in agricultural products,and the effects of sample loading solvent,p H,washing,elution solvent and elution volume on the adsorption and desorption conditions of organophosphorus pesticides were investigated.Finally,the established SPE-HPLC-MS/MS method based on Mo S2@MIPs for the determination of organophosphorus pesticides in different vegetables and fruits.The method exhibited good linearity(R~2?0.9913)and low limit of detections as low as 0.01?0.72 ng/m L.The experiment was repeated at different spiking levels(10 ng/m L,50 ng/m L and 100 ng/m L),and the recoveries were 77.9%?112.0%,relative standard deviations lower than 8.94%.This method not only had high sensitivity and selectivity,but also provided a new strategy for the enrichment and detection of other pollutants. |
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