Study On The Fabrication Of Electrochemical Sensor Based On Nanoparticle Doped Molecularly Imprinted Polymer And Its Detection Of Melamine And Chlorpyrifos In The Environment

With the continuous improvement of people's living standard,people's demand for dairy products is also increasing.However some illegal traders added some harmful additives to dairy products to seek profits.Such as the melamine,it will be transferred into the food,so that the food nitrogen content is high.Organophosphorus pesticides,as a broad-spectrum and efficient pesticide,are widely used in many countries.High toxic and high residual pesticides are gradually banned in agricultural production.Medium and low toxic pesticides,as excellent substitutes,are increasingly used.Chlorpyrifos?CPF?,a highly toxic broad-spectrum pesticide and herbicide,has become one of the most widely used organophosphorus pesticides in the current crop production activities.The toxic residues of chlorpyrifos in the environment and various agricultural products can enter the human body through enrichment and harm human health.Therefore,it is of great practical significance to develop a simple,rapid and effective method to detect melamine and chlorpyrifos.In this paper,chlorpyrifos,an organophosphorus pesticide,and melamine were used as template molecules.The properties of the prepared materials were characterized by scanning electron microscopy?SEM?,Fourier infrared spectroscopy?FT-IR?,cyclic voltammetry?CV?and differential pulsed voltammetry?DPV?.In addition,the experimental solution,the added concentration of template molecules,the pH value of the solution to be tested and the incubation time were optimized in the later experiment.The linear range and LOD of the template molecule were investigated under the optimal conditions.In addition,the repeatability,stability and selectivity of the sensor were also tested.Finally,the molecularly imprinted electrochemical sensor was successfully applied to the analysis and detection of the target in the actual sample.The main research contents of this paper are as follows:?1?Using melamine?Mel?as template molecule,methacrylic acid?MAA?as functional monomer,ethylene glycol dimethacrylate?EGDMA?as cross-linking agent,and 2,2-azo diisobutyronitrile?AIBN?as initiator,the molecularly imprinted polymer of melamine was prepared by non-covalent bonding method.Gold nanoparticles were introduced into the polymer to form a gold nanoparticle doped melamine imprinting complex?AuNPs@MIPs?,and then the polymer was mixed with graphite powder and liquid paraffin to make a carbon paste,which was filled into the cavity of ptfe electrode,and the sensor was successfully prepared?AuNPs@MIPs/CPE?.The prepared sensor was detected by electrochemical characterization,cyclic voltammetry?CV?,differential pulse?DPV?and electrochemical impedance?EIS?.Under the optimal experimental conditions,the linear detection range of melamine by the sensor was 1×10^-91×10^-4mol L^-1.,and the minimum detection limit?LOD?was 5.735×10^-10mol L^-1.Three structural analogues and three interference ions were used to determine the selectivity of the sensor,and the results showed that the sensor had a good selectivity for melamine.Finally,the sensor was successfully used in the analysis and detection of melamine in dairy products,and the recovery was 87%to 102%.?2?Melamine molecularly imprinted electrochemical sensor?MIPs/RGO/GCE?was successfully prepared by directly polymerizing a layer of melamine molecularly imprinted electrochemical sensor?MIPs/RGO/GCE?on the surface of a glass carbon electrode modified by RGO by electropolymerization with melamine?Mel?as the template molecule and o-phenylenediamine as the functional monomer.Electrochemical characterization,cyclic voltammetry?CV?,differential pulse?DPV?and electrochemical impedance EIS were used to measure the performance of the sensor.Under the optimum experimental conditions,the sensor to detect melamine range of0.5¹0?M,the two structural analogues and five kinds of interference ions existence condition,the vegetation sensor has good selectivity to the melamine,finally,the preparation of sensors successfully applied to the analysis of melamine in milk products detection,recovery is 93%¹02%.?3?Using chlorpyrifos?CPF?as template molecule,methacrylic acid?MAA?as functional monomer,ethylene glycol methacrylate?EGDMA?as crosslinking agent,2,2-azodiisobutyronitrile?AIBN?as initiator,the surface molecular imprinting method is adopted,the aggregation formation on the surface of modified silica?SiO₂-MPS?chlorpyrifos molecularly imprinted polymers,and then introduced to the preparation of multi-walled carbon nanotubes in polymer,the formation of multi-walled carbon nanotubes doped chlorpyrifos imprinting complex?MWCNTs@SiO₂-MIPs?,A sensor which can detect chlorpyrifos specifically was constructed by combining it with an electrochemical workstation.Electrochemical characterization,cyclic voltammetry?CV?,differential pulse voltammetry?DPV?and electrochemical impedance?EIS?were used to measure the performance of the sensor.Under the optimal experimental conditions,the linear detection range of this sensor for chlorpyrifos was 5.0×10^-125.0×10^-8mol L^-1,and the minimum detection limit was 8.1×10^-13mol L^-1?S/N=3?.The results of selective analysis of three structural analogs showed that the sensor has good selectivity to chlorpyrifos.Finally,the sensor was successfully applied to the analysis and detection of chlorpyrifos poisoning from apple and lettuce,and the recovery rate was 97.8%¹08.6%.