Fabrication Of Three Composite Modified Electrodes And Their Application In Taste Compounds Detection

The taste quality of food is closely related to the composition and content of its internal substances.So,it is of great significance to determine the contents of taste compounds in food quickly and accurately.Nowadays,the most traditional detection methods in the field of food quality detection include sensory evaluation method,high performance liquid chromatography and electronic tongue method.These methods still have some shortcomings,such as unstable evaluation results,expensive equipment,and long detection time.In order to explore the relationship between the types and contents of taste compounds and the taste information,and to establish a more systematic and comprehensive quality evaluation system for liquid food,this paper develops electrochemical sensors based on composite modified electrodes with high sensitivity,good selectivity,good stability and fast response time.The main contents and conclusions of this paper are as follows:（1）A novel Ni O nanoflower/polymethylene blue modified glassy carbon electrode was fabricated and taken as a non-enzymatic glucose sensor.This home-made glucose sensor combined the advantages of Ni O nanomaterial and PMB,and a series of characterization results indicated that the composite material exhibiting satisfactory catalytic activity towards glucose.The quantitative determination of glucose was carried out by chronoamperometric measurements method and showed linear ranges between 3-50μM and 50-80μM,with the limit of detection of2×10^-2μM（S/N=3）.Under optimal conditions,the sensitivity of the self-assemble biosensor was calculated to be 413.06μA cm^-2 m M^-1 for glucose.The selectivity of the modified electrode was investigated by chronoamperometry,and it was found that the addition of interfering substances had no significant effect on the response current,indicating the good selectivity of the Ni O/PMB modified electrode.The response peak currents of the five modified electrodes were similar,and the RSD was 7.0%,indicating that the modified electrodes had good reproducibility.After stored at 4°C for two weeks,the electrodes still retained more than 94%of the initial response,indicating that the Ni O/PMB modified electrodes had good stability.（2）A ZIF-8/Cu Co O₂ modified electrode was constructed for the detection of glutamic acid.The composite of ZIF-8 and Cu Co O₂ materials made the modified electrode have better comprehensive performance than bare electrode or single-component modified electrode.The reaction process of glutamic acid on the modified electrode was as follows:the amino group on the glutamic acid molecule combined with hydrogen ions in water to form a positively charged ion,and charge transfer occurs inside it;the carbon-hydrogen bond inβ-position in the original glutamic acid molecule was broken,and a conjugated double bond was formed with the carboxyl group;the carbon-nitrogen bond at theαposition was broken,and the amino group in the glutamic acid molecule was removed to generate NH₃ and E-glutamate.The detection of different concentrations of glutamate was carried out under the optimized experimental parameters,and the obtained response peak current was linearly correlated with the concentration of glutamate between 1-50μM（R²=0.99732）,and the detection limit was 3×10^-2μM.The selectivity of the modified electrode was investigated by differential pulse voltammetry,and it was found that the addition of interfering substances had no significant effect on the response current,indicating the good selectivity of the ZIF-8/Cu Co O₂ modified electrode.The response peak currents of the five modified electrodes were similar,and the RSD was 1.33%,indicating that the modified electrodes had good reproducibility.After stored at 4°C for two weeks,the electrodes still retained more than 98%of the initial response,indicating that the ZIF-8/Cu Co O₂ modified electrodes had good stability.（3）ZIF-67/CNTs/Si O₂ modified electrode was prepared for gallic acid detection.CNTs are wound around ZIF-67,and the particle size of Si O₂ was around 300 nm.The composite modified electrode had better performance than the bare electrode or the single-component modified electrode,due to the large surface area and excellent catalytic performance of ZIF-67,good conductivity of CNTs,the hydrophobicity of silica.Combining the theory of computational chemistry to analyze the response mechanism of the electrode to gallic acid,it was found that O12-H18 and O11-H17 are easier to break during the electrochemical oxidation of gallic acid,and the oxidation reaction of gallic acid occurs in the carboxyl pair.On the hydroxyl group of gallic acid,and the presence of Co can reduce the oxidation potential of gallic acid,indicating that the modified material has a catalytic effect on the oxidation of gallic acid.Under the optimized experimental parameters,the detection of gallic acid with different concentrations was carried out.The obtained response peak currents were linearly related to the concentrations of gallic acid.The associated linearity was ip（μA）=0.09009 c（μM）+3.96078（R²=0.99732）,the detection limit is2×10^-2μM,and the sensitivity is 593.33μA/（cm²·m M）and 274.76μA/mg.The selectivity of the modified electrode was investigated by cyclic voltammetry,and it was found that the addition of interfering substances had no significant effect on the response current,indicating the good selectivity of the ZIF-67/CNTs/Si O₂ modified electrode.The response peak currents of the five modified electrodes were similar,and the RSD was 1.75%,indicating that the modified electrodes had good reproducibility.After stored at at room temperature for two weeks,the electrodes still retained more than 96%of the initial response,indicating that the ZIF-67/CNTs/Si O₂ modified electrodes had good stability.（4）Since the contents of glucose,glutamic acid and gallic acid are different in Huangjiu of different ages,three prepared modified electrodes with good performance were formed into a sensor array,and the multi-potential step method was used.Based on two different feature extraction methods,combining dimensionality reduction algorithms such as PCA,LDA,SRP,GRP,LLE,and FA,with classification algorithms such as LR,ELM,and SVM,the electrochemical data were analyzed.Finally,the distinction and prediction of Huangjiu of different ages were successfully realized.