Fabrication And Application Of Magnetic Covalent Organic Frameworks In Food Safety Detection

Food safety is closely related to people’s health.Food safety problems such as abuse of food additives and mycotoxin contamination have potential threats to human health.Therefore,it is necessary to detect food additives and mycotoxins in food.Due to the complex matrix of food samples and the low concentration of target analytes,it need to develop sample pretreatment techniques with high enrichment efficiency and selectivity.Magnetic solid phase extraction（MSPE）has the advantages of simple operation,simple separation and compatibility,especially suitable for the analysis of complex food samples.In this paper,covalent organic framework materials were prepared by one pot method for MSPE propylparaben and ochratoxin A（OTA）in foods.Combined with high performance liquid chromatography（HPLC）,a new method for separation and analysis of propylparaben and OTA based on magnetic covalent organic framework materials was established.The main contents are as follows:（1）The Fe₃O₄@Dha Tab was synthesized by one-pot method and characterized by TEM,SEM,PXRD,FT-IR,VSM,N₂ adsorption-desorption,EDX element analysis,etc.The particle size of the Fe₃O₄@Dha Tab is 200-300 nm,and the thickness of the Dha Tab shell is 30 nm.It has good dispersibility and large adsorption capacity,and can maintain stability at high temperature.In the follow-up experiment,Fe₃O₄@Dha Tab was selected to investigate the MSPE of propylparaben and OTA.（2）An analytical method based on MSPE-HPLC-UV was developed for the determination of propylparaben in food.MSPE conditions were optimized.The optimal extraction results were obtained by adding 2 mg Fe₃O₄@Dha Tab into 3 m L propylparaben solution with p H 4,extracting for 5 min,then eluting with 1m L methanol.The MSPE-HPLC-UV method based on Fe₃O₄@Dha Tab afforded good linearity with LOD of 0.55μg/L and LOQ of 1.5μg/L.The method was used for the determination of propylparaben in beverage with a recovery of 97.0-98.3%.Therefore,Fe₃O₄@Dha Tab has the potential to be used as an efficient adsorbent for parabens in food samples.（3）Fe₃O₄@Dha Tab was used for MSPE OTA from food sample and determination of OTA by HPLC-FLD method.MSPE conditions were optimized,including the amount of adsorbent,extraction time,p H,ionic strength,elution solvent,etc.Under the optimal MSPE conditions,the developed Fe₃O₄@Dha Tab-based-MSPE-HPLC-FLD method for OTA displayed good linearity（0.1-800μg/L）with R²（0.996）and low limit of detection（0.03μg/L）.Fe₃O₄@Dha Tab still has good extraction performance after 6repetitions.The efficient and selective extraction of OTA depends on the large specific surface area and inherent porosity of COFs andπ-π,hydrogen bond and hydrophobic interaction between COF and OTA.The proposed method was applied to determine OTA in beer,Chinese Baijiu and vinegar with satisfactory recoveries（72-111%）and relative standard deviations（0.2-5.5%）.The results show that Fe₃O₄@COFs has the feasibility and potential in the pretreatment of mycotoxin samples.