Synthesis Of Magnetic Covalent Organic Framework Materials And Theiradsorption Technology For AFB₁ And T-2 Toxins

Mycotoxins are toxic secondary metabolites produced by various fungi,primarily Aspergillus,Fusarium and Penicillium.Aflatoxin is a secondary metabolite produced by Aspergillus flavus,which is highly toxic,immunosuppressive and strongly carcinogenic.Aflatoxin B₁（AFB₁）is the most toxic,carcinogenic,teratogenic and mutagenic aflatoxin to a variety of organisms.T-2 toxin is the most toxic type A trichothecenes with teratogenicity and weak carcinogenicity.AFB₁and T-2 toxins can contaminate water and grains and enter the human body through the food chain,causing harm to the body.Due to the complex composition of food matrix and the trace level of target substances,there is an urgent need to study adsorbents that can efficiently adsorb AFB₁and T-2 toxins.Covalent organic frameworks（COFs）are a new type of porous crystalline materials with the advantages of large specific surface area,good thermal/chemical stability,and adjustable pore size.In this paper,a new type of magnetic COFs composite material was synthesized,and combined with high performance liquid chromatography tandem mass spectrometry（LC-MS/MS）as the detection method,the adsorption and removal of AFB₁in water and the T-2 toxin in food were realized.adsorption enrichment.The main research contents and results are as follows:（1）Synthesis of Fe₃O₄@COFs materials.COFs and aminated Fe₃O₄magnetic nanoparticles were firstly synthesized by room temperature and hydrothermal methods,respectively,and then Fe₃O₄@COFs composites were synthesized by three methods.Method1 was to synthesize Fe₃O₄@COFs material by coupling COFs and Fe₃O₄magnetic nanoparticles via glutaraldehyde.The successful synthesis of the composites was demonstrated by electron microscopy,N₂adsorption-desorption curves,fourier transform infrared spectroscopy and other characterization means.The specific surface area was calculated to be 1293.32 m²g^-1based on the adsorption data of Brunauer-Emmett-Teller model（BET）Method 2 used polyacrylic acid（PAA）for surface modification of Fe₃O₄magnetic nanoparticles.The Fe₃O₄@COFs materials were synthesized by coupling with COFs after activation of the carboxyl group of Fe₃O₄by EDC/NHS.The synthesis of the composites was demonstrated by characterization means such as electron microscopy,and the specific surface area was calculated to be 545.41 m²g^-1based on the adsorption data of the BET model.The Fe₃O₄@COFs material of method 3 was synthesized by the precipitation polymerization method,and the TEM characterization showed that the morphological structure of the COFs was severely deformed,and the overall agglomeration was serious,which was quite different from the expected.Therefore,the Fe₃O₄@COFs material synthesized by this method was not used in next experiment.Theoretically,the larger the specific surface area is more favorable the adsorption.Therefore the Fe₃O₄@COFs material synthesized by method 1 was chosen for the next experiments.（2）Adsorb and remove AFB₁from water by Fe₃O₄@COFs.The synthesized Fe₃O₄@COFs were used as adsorbent to adsorb and remove AFB₁from water.The adsorption performance of Fe₃O₄@COFs for AFB₁was studied by adsorption isotherm and adsorption kinetics.The results showed that Fe₃O₄@COFs could effectively adsorb AFB₁,the adsorption could be completed within 10 min,the removal efficiency could reach more than 90%,and the maximum adsorption capacity reached 420μg mg^-1was obtained,with chemisorption being the main rate-limiting step.Reusability experiments showed that Fe₃O₄@COFs could be reused at least 8 times.The molecular simulations revealed that there were multiple interactions of“π-π”stacking and hydrogen bonding between COFs and AFB₁.The results of applying Fe₃O₄@COFs to real water samples showed that Fe₃O₄@COFs has good application effect in removing AFB₁from real water samples.（3）Adsorb and enrich T-2 toxin from food by Fe₃O₄@COFs.The synthesized Fe₃O₄@COFs were used as adsorbents to adsorb and enrich T-2 toxin from food by magnetic solid-phase extraction.The adsorption behavior exhibited fast adsorption rates and high adsorption capacities.The extraction conditions in the experiment were optimized.Finally,the dosage of Fe₃O₄@COFs was selected as 0.7 mg,the eluent was a mixed solution of acetonitrile and formic acid,and the elution time was 30 min for subsequent experiments.The adsorption performance of Fe₃O₄@COFs on T-2 toxin was investigated by adsorption isotherms and adsorption kinetics,and the results showed that Fe₃O₄@COFs could effectively adsorb T-2 toxin and the adsorption could be completed within 30 min.The results of reusability experiments showed that Fe₃O₄@COFs could be reused more than 10 times.The molecular simulation revealed that there were multiple interactions between COFs and T-2toxin in the form of“π-π”stacking and hydrogen bonding.The adsorption efficiency of magnetic COFs for the adsorption of T-2 toxin in vinegar reached more than 90%,and the spiked recoveries ranged from 83.44%to 88.60%,indicating its good application effect.