Preparation Of Thiazole Polymer Modified Electrode And Its Application In Biological Analysis

Ascorbic acid?AA?,dopamine?DA?,uric acid?UA?,epinephrine?EP?and nitrite?NO₂^-?are both coexisted in biological matrixes and are essential for human metabolic processes.Abnormal concentrations of these molecules in the body's metabolism can cause different diseases such as scurvy,gout,hypertension and Parkinson's disease,etc.Therefore,it is very important for their simultaneous determination.At present,the detection methods for these biomolecules mainly include:spectrometry,high performance liquid chromatography,electrophoresis and enzyme methods,etc.However,these methods have the disadvantages of low sensitivity and being easily interfered by other reducing substances.Although high performance liquid chromatography and spectroscopy can increase the sensitivity and specificity,but it also has a lot of shortcomings such as complex sample preparation procedures,lengthy analysis times,and large,expensive analytical instruments,etc.So that it can not be widely used.Similarly,electrophoresis and enzymatic methods have also been limited due to cumbersome procedures and high prices.Based on the electrical activity of these biomolecules and the advantages of electrochemical analysis methods such as rapidity,simplicity,high sensitivity,low cost and high selectivity,the electrochemical analysis methods for these biomolecules are becoming more and more important.However,these biomolecules often have higher,mutually close oxidation overpotentials on conventional glassy carbon electrodes and producing weak and overlapping oxidation peaks.Moreover,the electron transfer rate of these molecules is slow,these molecules and their oxidized products are easily absorbed on the surface of the glassy carbon electrode,so it greatly affecting the analysis effect.In order to improve the sensitivity and selectivity,a variety of materials have been coated on the electrode surface,such as conductive polymers,carbon nanotubes,graphene and metal nanoparticles,etc.Among various modified materials,thiophene,purine,aniline,pyrrole and other conductive polymers modified glassy carbon electrodes have simple preparation methods,high concentration of active groups,long service life,good selectivity and strong electrochemical response signals,etc.So it is widely used in molecular detection and analysis.In recent years,thiazole polymers have emerged in the electrochemical world.This work mainly focuses on the study of thiazole polymer modified electrodes.This paper includes three aspects as followed:1.The activated glassy carbon electrode?A-GCE?was prepared by using simple cyclic voltammetric?CV?scan of clean glassy carbon electrode?GCE?in 1 mol L^-1H₂SO₄ solution.In 0.1 mol L^-1 pH 7 phosphate buffer solution?PBS?,A-GCE can not only improve the oxidations of ascorbic acid?AA?,dopamine?DA?,uric acid?UA?and nitrite?NO₂^-?,but also resolve the weak and overlapped voltammetric responses of AA,DA,UA and NO₂^-into four sensitive oxidation peaks,the peak potential separation(?E_pa)of AA-DA,DA-UA and UA-NO₂^-are 0.16 V,0.15 V and 0.45 V,respectively,indicating the good electro-catalytic response of A-GCE toward AA,DA,UA and NO₂^-.Thus,the A-GCE can be used for the simultaneous determination of AA,DA,UA and NO₂^-in their mixture.Under the optimized experimental conditions,the linear concentration dependences of DPV current responses for AA,DA,UA and NO₂^-are observed in the concentration ranges of 5-2100,2-140,1-700and 10-1050?mol L^-1,with correlation coefficients of 0.9989,0.9968,0.9974 and0.9978,respectively.The detection limits?S/N=3?for AA,DA,UA and NO₂^-are 0.19,0.45,0.28 and 0.72?mol L^-1,respectively.The A-GCE has been applied to the simultaneous determination of AA,DA,UA and NO₂^-in serum samples with satisfactory results.2.A simple and sensitive electrochemical sensor for the determination of epinephrine?EP?,uric acid?UA?and nitrite?NO₂^-?in 0.1 mol L^-1 phosphate buffer solution?PBS,pH 7.0?by using cyclic voltammetry?CV?and differential pulse voltammetry?DPV?techniques was developed based on a 3-Amino-1,2,4-triazole modified glassy carbon electrode?ATA/GCE?.The modified electrode?ATA/GCE?exhibited excellent electrocatalytic activity for the electrochemical reaction of EP,UA and NO₂^-.The results shown that ATA/GCE could negatively shifted oxidation potentials,enhanced peak current responses,resolves the sluggish and overlapped voltammetric responses of EP,UA and NO₂^-into three strong and well-defined oxidation peaks,the potential difference between the oxidation peaks of each analyte exceeded 110 mV,which can be applied for the selective and simultaneous determination of EP,UA and NO₂^-in their mixture.Under the optimized experimental conditions,the linear dependences of DPV current responses were obtained for EP,UA and NO₂^-in the concentration ranges of 1-800?mol L^-1,1-450?mol L^-1 and0.5-2250?mol L^-1 with the correlation coefficients of 0.9981,0.9927 and 0.9993,and the corresponding detection limits of 0.15,0.19 and 0.23?mol L^-1?S/N=3?,respectively.In addition,the ATA/GCE also showed excellent reproducibility and long-time stability.Finally,the electrochemical sensor was successfully applied in the analysis of human urine and serum samples by using standard adding method with satisfactory results.3.A poly?3-Amino-1,2,4-triazole-co-2-methoxy amino-2-?2-amino thiazole?-4-acetic acid??ATA-AMTA?film modified glassy carbon electrode?GCE??ATA-AMTA/GCE?has been fabricated by using electrochemical copolymerization of 3-Amino-1,2,4-triazole?ATA?and 2-methoxy amino-2-?2-amino thiazole?-4-acetic acid?AMTA?.The results show that compared with the electrochemical behavior on the bare electrode,the peak current of oxidation peak is obviously increased and the peak potential difference(?E_pa)is 0.15 V,which can be applied for the simultaneous determinations of AA and EP in a mixture.Under the optimum conditions,the linear dependences of DPV current responses are observed for AA and EP in the concentration ranges of 1-3800?mol L^-11 and 0.5-650?mol L^-1 with the correlation coefficients of 0.9997 and 0.9989,respectively.The detection limits are0.16?mol L^-1 and 0.13?mol L^-11 for AA and EP,respectively?S/N=3?.The application of ATA-AMTA/GCE is demonstrated by simultaneously determining the concentrations of AA and EP in human urine samples by using standard adding method with satisfactory results.Through the above research,it can be seen that 3-amino-1,2,4-triazole has a good electrocatalytic effect on biomolecules such as ascorbic acid,dopamine,uric acid,epinephrine and nitrite.At the same time,when 3-amino-1,2,4-triazole is copolymerized with 2-methoxy amino-2-?2-amino thiazole?-4-acetic acid,it still has good catalytic effect and electrochemical behavior on biomolecules.Therefore,the application of thiazoles to the catalytic response of biomolecules to modified electrodes deserves more in-depth studies.