Study On The Multi-residues Detection Of Triazole Pesticides Based On Magnetic Nano Molecularly Imprinted Technology

Triazole pesticides are compounds,which contain 1,2,4-triazole ring,including fungicides,plant growth regulators,insecticides and herbicides.Due to the advantages of high efficiency,low toxicity and low residue,triazoles have been widely used to prevent and control the pests and diseases in vegetables,fruits,grains and so on.However,the improper or abuse use of triazoles may cause the high pesticides residues in agricultural products and environment,which could make a threat against food security and human health.Because of the matrix interferences,complex pretreatments are essential for traditional detection methods of triazoles,like LC-MS/MS.Therefore,it is necessary and significative to establish an efficient,quick,selective and high-throughput pretreatment method for triazoles to achieve the trace multi-residues detection in complex matrix samples.Molecular imprinting technique?MIT?is based on antigen-antibody biological recognition theory.Molecularly imprinted polymers?MIPs?can absorb targets selectively and be of excellent stability,resistance and reutilization,which could be used in the pretreatment as solid-phase extraction sorbent to achieve the trace analysis and detection in complex matrix samples.Molecularly imprinted-magnetic nano technology has the advantages of high selectivity and good seperation,which is suitable for the quick seperation and efficient enrichment for trace targets.Based on that,MIPs and magnetic molecularly imprinted polymers?MMIPs?for triazoles were prepared,and molecularly imprinted solid-phase extraction?MI-SPE?technology was applied in this study.The details are as follows:1.Based on the characteristics of triazole pesticides,the polymerization systems of MIPs were optimized,MIPs for 20 triazole fungicides/plant growth regulators were prepared,and the mechanism of polymerization was studied.The MIPs were prepared by precipitation polymerization using triadimefon as the template molecule,methacrylic as the functional monomer,trimethylolpropane trimethacrylate as the cross-linker and acetonitrile as the porogen,and the MIPs were used as the sorbents for MI-SPE column.The prepared MIPs were characterized by the ultraviolet spectroscopy,Fourier-transform infrared spectroscopy and scanning electronic microscopy.The adsorption capacity of MIPs was evaluated by Scatchard model,and the recognition mechanism of MIPs for targets was studied.The use conditions of MI-SPE column were optimized and the method of MI-SPE-LC-MS/MS for 20 triazoles in cucumber samples was established in this study.The results showed that,the average recoveries of 20 triazoles were in the range of 82.3%¹17.6%at three concentration levels?1,2,10?g/L?with standard deviation?RSD,n=5?of less than 14.7%.2.Fe₃O₄ magnetic nanoparticles were synthesized by coprecipitation method,and the magnetic nanoparticles were modified with amidogen or allyl respectively.Combining with the surface molecular imprinting technique,Fe₃O₄-NH₂@MIP and Fe₃O₄-CH=C₂H₄@MIP were successfully prepared.The magnetic molecularly imprinted polymers?MMIPs?were characterized via transmission electronic microscopy,Fourier-transform infrared spectroscopy,X-Ray diffraction and vibrating sample magnetometer.The results showed that Fe₃O₄-CH=C₂H₄@MIP was be of better dispersibility and regular shapes.The adsorption capacity of Fe₃O₄-CH=C₂H₄@MIP was evaluated by Scatchard model.The results showed that the composite materials contained two types of binding sites,the Q_max were4563.3?g/g and 9202.9?g/g,respectively.Based on the magnetic separation technique,an analytical method of MI-MDSPE-LC-MS/MS for the simultaneous determination of 20 triazoles in cucumber samples was developed.The results showed that the obtained recoveries were in the range of87.9%¹10.3%at three concentration levels.This new method can save the time and cost compared with SPE,making the rapid pretreatment of targets comes true.3.Based on the large specific surface area and active groups of graphene oxide?GO?,a novel composite material Fe₃O₄@SiO₂-GO was synthesized by using magnetic silica?Fe₃O₄@SiO₂?as the carrier.Based on the surface molecular imprinting technique,the Fe₃O₄@SiO₂-GO@MIP for difenoconazole was prepared and characterized by transmission electronic microscopy.The purication and enrichment for difenoconazole in cucumber samples were studied by using these polymers as the sorbents of magnetic dispersive solid-phase extraction,and a rapid detection method of surface-enhanced Raman spectroscopy?SERS?technology was initially established using Fe₃O₄@SiO₂-GO@MIP as pretreatment material.The limit of quantification of the method was 0.1mg/kg,which could meet the detection requirements of maxium residue limit for difenoconazole in cucumber samples.