Study On Multi-residue Detection Of Strobilurin Fungicides Based On Molecular Imprinting And Metal-organic Frameworks

Strobilurin fungicides are derivatives derived fromβ-methoxyacrylic acid,with broad spectrum,high efficiency and high activity,which prevent the synthesis of cellular energy by inhibiting electron transport between cytochrome b and c1 in fungi.However,the residue in the environment resulted from the misuse and overuse of strobilurin fungicides poses a serious hazard to human health and ecological safety.In order to monitor strobilurin fungicides in complex matrices of environmental and agricultural products,this research used molecularly imprinting technology with specific recognition and metal organic frameworks with high extraction efficiency.A new type of molecularly imprinted polymers of strobilurin fungicides was firstly prepared,and then magnetic metal organic frameworks/molecularly imprinting hybrid complexes were prepared.The high-throughput,highly sensitive,rapid and simple methods of solid phase extraction and magnetic solid phase extraction with high performance liquid chromatography-tandem mass spectrometry for the detection of multiple residual strobilurin fungicides were established,respectively.The results of this study are as follows:1.Molecularly imprinted polymers（MIPs）of strobilurin fungicides were prepared by employing azoxystrobin as template molecular,methacrylic acid as functional monomer and trimethylolpropane triacrylate as cross-linker.The MIPs were characterized by scanning electronic microscopy and Fourier-transform infrared spectroscopy and evaluated by binding and selective adsorption experiments.Molecularly imprinted solid-phase extraction（MISPE）packed with MIPs and the loading solvent,washing and elution conditions were optimized by single factor test.The optimized conditions were used to enrich the fungicides in cucumber and peach samples,and the repeatability of MISPE column was investigated.The results showed that:the prepared MIPs were spherical particles and their diameter was about 200 nm with typical characteristic groups.The developed MISPE-HPLC-MS/MS method showed good linear relationship,the correlation coefficients were greater than 0.9900,and good recoveries（70.0%-114.0%）with relative standard deviations in range of 1.0%-9.8%（n=3）spiked at three different levels(10,50,and 100 ng g^-1).The detection limit（signal/noise=3）ranged from 0.01 to0.08 ng g^-1.These results showed that the established method was efficient,highly sensitive,simple and easy to operate,and had a good application prospect for the detection of trace strobilurin fungicides in agricultural products.2.Magnetic metal-organic framework matrix composites（Fe₃O₄/ZIF-8）were prepared by in situ polymerization using zinc ion as the central ion and 2-methylimidazole as the organic ligand.By scanning electronic microscopy,Fourier-transform infrared spectroscopy,X-ray diffraction and vibrating sample magnetometer,the results showed that ZIF-8 was regular square shape with a diameter of about 150-200 nm,and Fe₃O₄nanoparticles attacked on the surface of ZIF-8.The Fe₃O₄/ZIF-8 was used as adsorbents in magnetic solid phase extraction（MSPE）,the effects of adsorption and desorption conditions on the recoveries were investigated.And the optimal conditions were determined（40 mg Fe₃O₄/ZIF-8,40 m L water sample,adsorption time for 10 min,1%FA-methanol as elution solvent for 3 m L）.The established MSPE-HPLC-MS/MS had good correlation coefficient of the linear relationship was greater than 0.9935,and the recoveries obtained from the three groups of spiking experiments(10,20 and 50 ng m L^-1)were 80.8%～119.0%,with a relative standard deviation of 1.2%-6.7%.The established method provided the detection of strobilurin fungicides in environmental samples by magnetic solid phase extraction-chromatography tandem mass spectrometry with advantages of more rapidly,simply,and fewer organic reagents.3.Through surface molecularly imprinting preparation method,magnetic metal-organic frameworks/molecularly imprinted hybrid complexes（M-MOFs/MIPs）were prepared by molecular imprinting polymerization on the surface of magnetic metal-organic matrix composites.The structure of M-MOFs/MIPs was characterized by scanning electron microscopy and transmission electron microscopy.The binding experiments showed that M-MOFs/MIPs possessed a faster adsorption rate（only 5 min）and the apparent maximum adsorption capacity obtained were 526.3 mg g^-1and 205.9 mg g^-1,respectively.MSPE as pretreatment technology,the adsorption and elution conditions were optimized.The dosage of adsorbent was 30 mg,adsorption time for 10 min,loading solvent was ACN-H₂O（20:80,v/v）,loading p H=7,elution conditions was 0.5%FA-ACN eluted for 3 m L were determined.The M-MOFs/MIPs-MSPE-HPLC-MS/MS method for detection strobilurin fungicides in fruit and vegetable samples（apple,peach,pear,radish,cauliflower,and potato）was established.The results showed that good recoveries（75.0%-107.9%）with relative standard deviations in range of 1.8%-6.6%（n=3）spiked at three levels(10,20 and 50 ng g^-1).The established method provided a new idea for the efficient enrichment of a variety of strobilurin fungicides in agricultural products.