Preparation Of Molecularly Imprinted Composite And Its Application In Organophosphorus And Organochlorine Pesticide Detection

With the deepening of economic globalization,food safety has become a hot issue in the food production,processing and distribution system.Pesticide residue is an important factor that endangers food safety.The detection of pesticide residue has aroused the interest of interdisciplinary research fields such as chemistry,material science and biological science.Sensors based on molecularly imprinted polymer(MIP)overcame many of the limitations of traditional detection methods and provided an opportunity for efficient,sensitive and low-cost detection.With highly specific molecular recognition and high stability under harsh chemical and physical conditions,MIPs has been used in electrochemical,optical and quality-sensitive sensors as an alternative to biological receptors for food analysis.In this paper,based on molecular imprinting technology,a rapid and trace detection method for pesticide residues was studied.The specific contents are as follows:(1)The Fe₃O₄ modified with oleic acid was used as the magnetic carrier,bisphenol A was used as the virtual template to make up for the defect of template leakage,and dopamine was used as the functional monomer to directly synthesize homogeneous,monodisperse and super-paramagnetic molecularly imprinted polymer(MMIPs)on the magnetic Fe₃O₄core surface in one step.Under ultrasonic condition,the material was eluted with 3%acetic acid and 20%acetonitrile in aqueous solution in batches for several times to form the hole with highly selective recognition of 4,4'-DDT.The superparamagnetic properties of dopamine-coated magnetic Fe₃O₄ molecularly imprinted polymer nanoparticles(PDA@Fe₃O₄-MIP MNPs)were used to preconcentrate and separate the analyte,and the analyte 4,4'-DDT was selectively captured onto the composite surface by PDA@Fe₃O₄-MIP MNPs.Using the classic three-electrode system,molecularly imprinted polymers(MIPS)with different concentrations of 4,4'-DDT were modified on the working electrode to construct an electrochemical sensor.The electrochemical impedance changed after adsorption,and it was applied to the separation and detection of organochlorine pesticide residues in radish.This method also has a certain degree of universality,which provides a convenient and universal method for constructing a simple and unlabeled pesticide residue sensing platform.(2)Fluorescence-molecularly imprinted polymer(FL-MIP)has been synthesized in a simple way.All the components,including fluorescent nanocrystals(LaVO₄:Eu³⁺NPs),magnetic nanoparticles,chlorpyrifos and polystyrene-co-methacrylic acid were self-assembled into composite nanocrystals by ultrasound-assisted method.The fluorescence would be quenched when the template molecule was recombined to the recognition site.Based on this,FL-MIP was applied to the direct fluorescence quantification of chlorpyrifos.FL-MIP nanospheres have the advantages of good selectivity,small particle size and small mass transfer resistance.At the same time,this study provides a new general strategy for the preparation of other multifunctional(luminescent and magnetic)inorganic materials.The organic MIP nanocomposites are ideal for biomedical/chemical sensing due to their high selectivity.