Studying On The Construction Of Electrochemical Sensors Based On Nanomaterial For Antibiotics Detection And Mechanism

Antibiotics are widely used in livestock and poultry farming due to the low price and effective treatment.In recent years,the misuse and abuse of antibiotics has become more and more serious,which has seriously threatened food safety and human health.Therefore,in order to ensure food safety and protect human body from injury,to establish a rapid and sensitive detection method for antibiotics is very necessary.Most of the traditional detection methods of antibiotics have problems such as expensive instrument,long analysis time and complicated pretreatment,while the electrochemical analysis method has the advantages of simple equipment,fast analysis speed and simple pretreatment.In this study,nanocomposites with excellent electrocatalytic performance were synthesized and used to modify the surface of electrodes.Five electrochemical analysis methods with high sensivity were developed for rapid detection of antibiotics in animal derived food.The selectivity,accuracy and application of the analytical methods were evaluated.The electrochemical reaction mechanism of antibiotics was explored.The main research results are as follows:1.The construction of an electrochemical sensor based on ordered mesoporous carbon for detection chloramphenicolIn this study,a simple and sensitive three-dimensional voltammetric sensor was constructed for the determination of chloramphenicol（CAP）.First,ordered mesoporous carbon nanocomposite was introduced onto a glassy carbon electrode（GCE）to improve the electron transport performance.Then,the peroxidation treatment of polydopamine increased the negative charge on the surface of polydopamine.Finally,the electrode surface was modified withβ-cyclodextrin through electrochemical polymerization.The developed sensor was investigated with square wave voltammetry（SWV）and cyclic voltammetry（CV）,and exhibited excellent electro-catalytic property towards CAP.Under optimal conditions,the method offered a wide current response for CAP from 5.0×10^-7 to 5.0×10^-4 mol L^-1 and the limit of detection（LOD）was 2.0×10^-7mol L^-1.Milk powder and bee pollen samples spiked with CAP were extracted and then determined using the method with satisfactory recoveries of 80.0%-101.6%.The method was also used to determine CAP residues in real milk and honey samples,and the results correlated well with those obtained using high-performance liquid chromatography（HPLC）.2.Ultrasensitive determination of sulfathiazole using a molecularly imprinted electrochemical sensor with Cu S microflowers as an electron transfer probe and Au@COF for signal amplificationIn this work,an imprinted sensor employing Cu S as a novel signal probe was successfully developed for ultrasensitive and selective determination of sulfathiazole（STZ）.First,Au@COF with good conductivity was introduced on GCE surface to amplify the signal,and then the reduction probe Cu S was immobilized on the electrode surface.A molecularly imprinted film was modified on surface of the modified electrode by electropolymerization.Under optimized testing conditions,the proposed sensor offered a linear DPV response to STZ over a very wide concentration range(1.0×10^-4-1.0×10^-11 mol L^-1),with a LOD of4.3×10^-12 mol L^-1.Fodder and mutton samples spiked with STZ were analyzed using this sensor,and the satisfactory recoveries ranging from 83.0%to 107.2%were obtained.In addition,the proposed sensor was used to determine the concentration of STZ in chicken liver and pork liver,with quantification results being near identical to those determined by HPLC.3.Synthesis of high conductivity NH₂-CNT@COF and its application and mechanism in the electrochemical detection of furazolidoneIn this study,a facile one-pot strategy for COF@NH₂-CNT with core-shell structure and high electrical conductivity at room temperature was developed.The COF@NH₂-CNT was modified on the GCE surface to establish a sensitive electrochemical method for detection furazolidone.The obtained sensor offered excellent analytical performance for the detection of the nitrofuran antibacterial agent furazolidone.The sensor offered a wide range furazolidone detection range from 0.2μmol L^-1 to 100μmol L^-1,with a low LOD of 7.75×10^-8mol L^-1.The recovery test was performed in chicken and lamb samples with satisfactory recoveries ranged from 87.8%to 126.9%.The furazolidone residues in beef and pork samples were determined using the method and HPLC.There was no significant difference between the two methods.The ability of the COF@NH₂-CNT to efficiently adsorb furazolidone was a key to high sensitivity and fast response of the sensor platform.Results encourage the wider use of covalent organic framework（COF）in electrochemical sensor development.4.The synthesis of COF@CB@MPDA and the application and mechanism in the electrochemical detection of ciprofloxacinIn this study,COF and carbon black（CB）were used as supporting vectors to synthesize COF@CB@MPDA with high conductivity and good dispersion at room temperature.The synthesis conditions of COF@CB@MPDA and the detection conditions of the method were optimized.The effective active area before and after the electrode modification was calculated by CV,and it was inferred that the oxidation mechanism of ciprofloxacin was involved by 2protons and 2 electrons.Under the optimum conditions,the sensor showed a good linear relationship with CF in the concentration range of 0.5-100μmol L^-1,and the LOD was 9.53×10^-8 mol L^-1.The recovery rate of milk samples was 93.8%-104.7%.The residue of CF in milk powder samples was determined by this method and HPLC respectively.There was no significant difference between the results obtained by two methods.5.A selective molecularly imprinted electrochemical sensor with GO@COF signal amplification for the simultaneous determination of sulfadiazine and acetaminophenIn this work,the development of a simple and sensitive electrochemical sensor for the simultaneous determination of SDZ and AP is described.The GO@COF nanocomposite was first immobilized on a GCE,after which a polypyrrole MIP was electrodeposited on the modified electrode.The resulting electrochemical sensor（denoted as MIP/GO@COF/GCE）showed a strong current response to both SDZ and AP in phosphate buffer at p H 7.0.Under optimal testing conditions,linear calibration curves were obtained over the concentration range 0.5-200μmol L^-1 for SDZ and 0.05-20μmol L^-1 for AP,with LOD being 0.16μmol L^-1and 0.032μmol L^-1,respectively.Beef and fodder samples spiked with SDZ and AP were extracted in ethylacetate,then the SDZ and AP in the extracts quantified using the MIP/GO@COF/GCE sensor.Recoveries were excellent,ranging from 82.0-108.0%.The same method was also employed to determine SDZ and AP residues in pork and chicken samples,with the results correlating well with those obtained using HPLC.