Preparation Of 2,4-dichlorophenoxyacetic Acid Molecularly Imprinted Material And Its Application In Food Samples Analysis

The low concentration of 2,4-dichlorophenoxyacetic acid is used to promote plant growth,and its high concentration is used as herbicide.The compound can enter environment and human body through food chain,etc.,and cause harm to biological system.Its concentration in the environment and food samples is very low with serious matrix interference.Therefore,it is necessary to develop a simple and efficient enrichment method for accurate quantification.The molecular imprinted polymer is a kind of material with specific recognition effect on the target analyte and good selectivity.Therefore,we have done the following work:1.The magnetic metal organic framework molecularly imprinted material was prepared,separated by an external magnetic field,and successfully used for the enrichment of 2,4-dichlorophenoxyacetic acid in vegetable samples.First,the magnetic ZIF-8 was prepared by solid-phase grinding as the base,using 2,4-dichlorophenol as the pseudo-template molecule,3-aminopropyltriethoxysilane as the functional monomer,and the molecularly imprinted material Fe₃O₄@ZIF-MIP was synthesized by sol-gel method and virtual template method at room temperature.The dynamic adsorption of Fe₃O₄@ZIF-MIP is consistent with the quasi-second-order kinetic model,and the adsorption capacity has a good correlation with the Freundlich isotherm model.When the concentration of 2,4-dichlorophenoxyacetic acid is 500μg/m L,the adsorption capacity of Fe₃O₄@ZIF-MIP is 120.31 mg/g with the imprinting factor about3.64,and it can be reused at least 6 times.2.We synthesized a molecularly imprinted composite membrane material using organic membranes.Combined with a commercial filter head for solid-phase extraction,2,4-dichlorophenoxyacetic acid was enriched and separated at the same time in vegetables samples.First,a nylon filter membrane was used as a substrate,and a layer of mesoporous silicon was deposited on it,then the molecular imprinting material MIPM was synthesized on the surface of the mesoporous silicon membrane.The imprinting factor of the material is 1.78.The material combined with the filtering device can be used as a disposable 2,4-dichlorophenoxyacetic acid filter.Because the shape and size of the filter membrane can be changed,the method has good universality.3.We prepared a polyvinyl alcohol based 2,4-dichlorophenoxyacetic acid molecularly imprinted self-supporting material.The molecularly imprinted powder was synthesized according to the above experimental method.Then it was embedded in the polyvinyl alcohol matrix to get the molecularly imprinted monolithic material MIPF by freeze-drying.The dynamic adsorption of 2,4-dichlorophenoxyacetic acid by MIPF is consistent with the quasi-second-order kinetic model,and the adsorption process is consistent with the Freundlich isotherm model.The theoretically calculated maximum adsorption capacity of the material is 77.52 mg/g with the imprinting factor 1.81.It can be reused at least 6 times.