Preparation Of Molecularly Imprinted Electrochemical Sensor For Tea Branch Biomass Charcoal And Its Detection Of Norfloxacin Residues In Animal Food

Irregular use in the actual livestock breeding process will lead to residues of norfloxacin（NFX）in animal-derived foods,which will endanger human health.Therefore,there is an urgent need to establish a new technology that is green,accurate,and can determine NFX residues in animal-derived foods in situ.While electrochemical sensors are favored by researchers in the development of rapid food safety detection methods,their specificity depends mainly on the recognition element,but the performance parameters of the detection process,such as sensitivity and detection limit,depend to some extent on the physicochemical properties of the sensor interface modification materials.In this paper,a bifunctional monomeric electrochemical sensor was successfully developed by using agricultural waste tea tree branches as the carbon source,preparing tea tree branch biomass carbon for the modification of glassy carbon electrode（GCE）by chemical activation method,and preparing molecularly imprinted polymer（MIP）by electropolymerization method.The molecularly imprinted polymer（MIP）was prepared by electropolymerization,and a bifunctional monomeric electrochemical sensor was successfully developed for the detection of norfloxacin residues in animal-derived foods.The main findings of the study are as follows:1.Tea tree branches were carbonized at high temperature（TBC）and then prepared with potassium carbonate to prepare tea tree branch biomass carbon（K-TBC）.The obtained TBC and K-TBC were characterized in detail by scanning electron microscopy,X-ray diffraction,infrared spectroscopy,X-ray photoelectron spectroscopy and nitrogen adsorption-desorption curves,and the results showed the graphitic nature of the TBC and K-TBC structures and verified the successful pore formation of the activator potassium carbonate.The specific surface area of K-TBC made by activation with potassium carbonate was experimentally demonstrated to be as high as 1214.68 m²/g.In addition,the sensor was characterized by instrumental means such as scanning electron microscopy and electrochemical scanning,which demonstrated the successful preparation of MIP/K-TBC/GCE sensor.2.To investigate the effect of K-TBC prepared under optimal conditions on the conductivity of the modified electrode,cyclic voltammetry was used,and the difference in peak current between the modified electrode and the bare electrode in the probe solution was used as an indicator.Secondly,the preparation conditions of the MIP/K-TBC/GCE sensor were optimized by differential pulse voltammetry,using the difference in peak current before and after adsorption of the prepared sensor in1×10^-7mol/L NFX standard solution as the judgment index,and the results showed that:The pH value of the electropolymerization solution was 3.5,the ratio of bifunctional monomers was 3:2,the ratio of template molecules to functional monomers was 5:15:15,the number of electropolymerization segments was 25,the scanning rate of electropolymerization was 75 m V/s and the elution time was 12 min as the optimal preparation conditions.3.Electrochemical sensors with different modification stages were used for NFX detection,and the prepared MIP/K-TBC/GCE sensors significantly enhanced the response signal.To investigate the recognition response of the MIP/K-TBC/GCE sensor for NFX under electrochemical conditions and the recognition mechanism followed,the reaction kinetics of the modified electrode in the imprinting reaction was deduced:the recognition of NFX by the MIP/K-TBC/GCE sensor is an irreversible anodic oxidation reaction（1.128 V）,and this electrochemical reaction follows a mixed adsorption-diffusion mechanism with more significant adsorption control.effect is more pronounced,and both electron transfer number and proton number change during the reaction are approximately 1.4.After optimization of the detection conditions（pH of the detection system was5.0,adsorption time was 4 min）,the sensor showed good linear current response for NFX concentrations in the ranges of 0.1～0.5 nmol/L and 0.5～100 nmol/L,with detection limits as low as 0.028 nmol/L.The sensor successfully detected NFX residues in spiked milk,honey and pork samples The recoveries ranged from 85.9%to 101.7%with RSD<4.05%,which was consistent with the performance of the HPLC-FLD control test.In addition,the prepared sensor has a short detection time（4min）,good selectivity,good anti-interference ability,good stability and low price,which can provide a theoretical and practical basis for the practical monitoring of NFX residues.