Preparation And Adsorption Mechanism Of Novel Functional Organic Porous Materials For High Efficiency Enrichment Of Pesticide Residues

Pesticides can effectively prevent and control plant diseases,pests,and grass pests in plant protection.However,the problem of pesticide residues caused by their large-scale use can have potential impacts on water and soil environments,thereby threatening human health.Developing fast,sensitive,and efficient method for detection of pesticide residues is of great significance.The commonly used technologies for pesticide residue detection include chromatography,spectroscopy,immunoassay,and electrochemical sensor methods.High performance liquid chromatography（HPLC）is widely used in the formulation of national standards for pesticide residue detection due to its advantages of high sensitivity and good reproducibility.Electrochemical sensing detection technology has the characteristics of low cost,fast and convenient,and strong selectivity,making it a promising technology in the field of pesticide residue analysis.As the actual sample matrix is complex and the pesticide residue content is generally low,sample pre-treatment becomes a key step before analysis and detection,which is used to reduce the matrix interference increase the concentration of the target analytes and improve the detection sensitivity.Solid phase extraction（SPE）and magnetic solid phase extraction（MSPE）have the advantages of simple operation,short extraction time and less amount of organic solvent,making them the two commonly used sample pretreatment techniques.Commercial solid phase extraction adsorbent has some shortcomings,such as low extraction efficiency and selectivity,so it is of great significance to develop new efficient adsorbent materials.The kinds of pesticides are very large,which possess different structures and physical chemical properties.How to reasonably regulate the surface physical and chemical properties of adsorbents,such as pore structure,hydrophilicity and polarity,according to the molecular structure characteristics of pesticides,so as to achieve efficient and highly selective enrichment,and to clarify the relationship between their structures and adsorption properties has become a key scientific problem to be solved.Phenylurea,triazine herbicides,neonicotinoid insecticides and benzimidazole fungicide are several commonly used pesticides with different structures.Based on a systematic review of relevant literature,this work designed and prepared several organic porous materials based on the structural characteristics of the target pesticides.They were used as（magnetic）solid-phase extraction adsorbents or electrode materials for enriching pesticide residues from vegetables and environmental water samples prior to HPLC and electrochemical sensing detection.The main research works are as following:1.Based on the structural characteristics of phenylurea herbicides that can be used as hydrogen bond receptors and contain halogen bonds,fluorinated and carboxy-functionalized hypercrosslinked organic polymer（FBPA-PMDA）was synthesized by Friedel-Crafts acylation using hexafluorobisphenol A（FBPA）as the monomer and pyromellitic anhydride（PMDA）as the crosslinking agent.The functionalized material was used as an SPE adsorbent for the separation and enrichment of phenylurea herbicides（PUHs）in complex sample matrices.The method for the trace determination of four PUHs in beverage and lettuce samples was established by HPLC-UV method.Under the optimal conditions,the linear response range for the four PUHs was in the range from 0.03 to 200 μg/L for the beverages and 5.0-200 ng/g for celtuce,respectively.High sensitivity was achieved,with the LOD of 0.01-0.025 ng/mL for beverages and 1.70 ng/g for celtuce.The method recoveries of the actual samples were in the range of 80.5%to 120.0%（RSD≤6.1%）.The systematic study of the adsorption behavior and mechanism of PUHs provides guidance for the efficient enrichment of PUHs in complex substrates.2.A series of novel magnetic HCPs（CD-Ps-MHCPs）were synthesized by using the βCD-graft-styrene hyper-crosslinked polymers（CD-Ps）as monomer and three rigid crosslinkers in response to the characteristics of hydrophobic inner cavity and hydrophilic outer surface of β-cyclodextrin（β-CD）.The quantitative analysis of triazine herbicides（THs）in river water and vegetable samples（zucchini,Chinese cabbage）was successfully achieved by using CD-Ps-MHCP2 as MSPE adsorbent with HPLC-DAD detection method.The results showed that the van der Waals force,hydrogen bonds,hydrophobic interaction,andπ-π stacking interaction between THs and CD-Ps-MHCPs comprehensively affect the enrichment effect of the adsorbent.Under the optimal extraction and desorption conditions,the method showed low LODs（0.05-0.15 ng/mL for river water and 0.31-3.10 ng/g for vegetable samples）and good reproducibility（RSDS≤6.0）.It provided theoretical and experimental guidance for efficient estimation,rapid separation and sensitive detection of trace THs residues in complex samples.3.Based on the structural characteristics of neonicotinoid insecticides,four novel hydroxyl functionalized HCPs（OH-HCP1,OH-HCP2,OH-HCP3 and OH-HCP4）with tunable hydrophilic-hydrophobic surface have been designed and fabricated for the first time using natural product luteolin as a monomer and biphenyl dichlorobenzene（BCMBP）as a crosslinking agent.OH-HCP3 has high affinity and adsorption properties for neonicotinoids（NEOs）.The adsorption mechanism and behavior of OH-HCP3 on NEOs were systematically investigated.It is found that hydrogen bond interaction,polar interaction,and Lewis acid base interaction are dominant,supplemented by pore adsorption.The OH-HCP3SPE/HPLC method was established to achieve the extraction,concentration,and analysis of NEOs in environmental water and edible fungi.This method had a wide linear range of 0.06100.0 ng/mL for lake water and 1.5-100.0 ng/g for edible fungi.Low LOD was achieved in the range of 0.02-0.08 ng/mL for lake water and 0.50-0.80 ng/g dible fungi,while the LOQ were 0.06-0.25 ng/mL and 1.50-2.50 ng/g,respectively.The method recoveries were 85.1112%.This work provides novel design ideas and application guidance for synthesis of hydroxy-functionalized HCPs（OH-HCPs）.4.Three hydroxyl-functionalized magnetic hyper-crosslinked polymers（EA-MHCPs）was prepared using biomass ellagic acid（EA）as monomer.EA-MHCP1 possesses large surface area,strong magnetism,and great neonicotinoid extraction capacity.Rapid enrichment and determination of four trace NEOs in water and lettuce samples were achieved by using EA-MHCP1 as MSPE adsorbent combined with HPLC.At optimized conditions,the linear ranges of four NEOs in water and lettuce samples were 0.06-100 ng/mL and 2.5-250 ng/g,respectively,and the LOD was 0.02-0.03 ng/mL and 0.8-3.2 ng/g,respectively.Method recoveries were in the range of 80.0%and 116%（RSD ≤7.1%）.5.An electrochemical sensor using graphene/Ni-MOF derived porous carbon（G-Ni/C）as the electrode material was successfully synthesized and used for the sensitive determination of carbendazim（CBZ）.The combination of graphene and the Ni-MOFderived porous carbon material not only prevents the agglomeration of graphene,but also improves the conductivity of the graphene,further improving the electrocatalytic activity and sensitivity of CBZ sensing.Under optimal conditions,the linear range of this method was range of 0.04 to 10.0 μM(7.6 × 10^-6-1.9× 10^-3 mg/mL)with a low LOD of 8.9 nM(1.7×10^-9mg/mL).The sensor has been successfully used for the quantitative detection of CBZ in pond water and fruit juice samples,with a method recovery of 91.3 to 111%.This method has the advantages of good reproducibility,strong selectivity and short determination time,which provides guidance for realizing the rapid detection and real-time analysis of pesticide residues.6.Nickel-doped nano-porous carbon（Ni/C）was prepared by direct calcinating Nibased metal organic framework（Ni-MOF）.The Ni/C/GCE sensor was developed for the selective trace determination of acetaminophen（AP）in human serum and urine.The Ni/C nanoporous carbon materials have plentiful catalytic active sites,ordered mesoporous structures and large specific surface areas,which endow the constructed Ni/C/GCE sensors with excellent performance in the quantitative analysis of AP.