| In recent years, electrochemical detection methods have attracted a lot of attention and widely used in the aspects of food safety, clinical medicine and environmental protection due to high sensitivity, rapid response and low cost.In this study, carboxyl functionalized multi-walled carbon nanotubes(MWCNT-COOH) modified glassy carbon electrode(MWCNT-COOH/GCE), multi-walled carbon nanotubes(MWCNT) and ionic liquids(IL) 1-butyl-3- methylimidazolium hexafluorophosphate([BMIM][PF6]) modified glassy carbon electrode(MWCNT-IL/GCE) and amino-functionalized multi-walled carbon nanotubes(MWCNT-NH2) and [BMIM][PF6] modified glassy carbon electrode([MWCNT-NH2]-IL/GCE) were used to study the electrochemistry behaviors of thiabendazole(TBZ), pyrimethanil(PMT) and faropenem(FAR), respectively. The modified electrodes were successfully applied in real samples determination with satisfied results. The primary research work is as follows:(1)A MWCNT-COOH/GCE was fabricated in this paper. The direct electrochemistry behavior of TBZ on the modified electrodes were investigated by cyclic voltammetry(CV) and differential pulse voltammetry(DPV). MWCNT- COOH/GCE exhibits an enhanced effectiveness for the the redox of TBZ in phosphate buffer solution(p H=6.0). The electrochemical mechanism of TBZ was acquired from the relationship between peak current and scan rate and the effect of solution p H on the redox of TBZ at MWCNT-COOH/GCE. The electrochemical reaction involved two electron transfer, accompanied by two protons. The electrode process was adsorption-controlled and chemically reversible. Factors affecting the response of TBZ, such as solution p H, accumulation conditions and the amount of modifier are optimized for the determination of TBZ. Under optimized conditions, this constructed sensor exhibited good relationships with TBZ concentration range from 5.0×10-7 to 9.8×10-5 mol/L, and the detection limit was 3.0×10-7 mol/L(S/N=3). The MWCNT-COOH/GCE showed a good reproducibility and stability. The recoveries determined were in the range from 96 % to 110 %, suggesting that the proposed method used for the determination of TBZ in real samples was reliable, effective and accurate.What’s more important, the interaction between TBZ and human serum albumin(HSA) was investigated by electrochemical method base on the decrease of peak current of TBZ when HAS was mixed. It was proposed that TBZ and HSA formed an electro inactive complex. Both binding number(n=2) and binding constant(KA=2.09×109 L/mol) were obtained. The molecular modeling studies were also carried out to clearly recognize the interaction between TBZ and HSA on molecular level. The results of modeling indicated that there is a large hydrophobic cavity in subdomain IIA of HSA to accommodate TBZ and the main interaction between TBZ and HSA was hydrophobic and electrostatic. It is helpful for us to understand the pharmacokinectics of TBZ.(2)A simple and sensitive electroanalytical detection method for PMT using MWCNT-IL/GCE was developed. The experimental results showed that the oxidation current of PMT at MWCNT-IL/GCE was almost three times larger than that at bare GCE. The introduction of IL improve the electrochemical performance of MWCNT obviously which could be attributed to the synergistic effect of MWCNT and IL, leading to increase the determination sensitivity and decrease the limit of detection. This kind of synergistic effect could enhance the electron transfer rate because of the high conductivity of both MWCNT and IL. The oxidation current of PMT at MWCNT-IL/GCE was an adsorption-controlled and totally irreversible electrode reaction. The electron transfer number is around 2. Under the optimum conditions, this electrochemical sensor exhibited two linear relationships with the concentration of PMT in the range from 1.0×10-7 to 1.0×10-4 mol·L-1, and the detection limit was 1.6×10-8 mol·L-1(S/N=3). The fabricated electrode has been successfully applied to the determination of PMT in real samples and exhibited good reproducibility, stability and anti-interference.Moreover, electrochemical impedance spectroscopy(EIS) and spectroscopic approachs were used to investigate the binding of PMT to HSA. The results demonstrated that the interaction between PMT and HSA was a new complex formation process. Both binding number and binding constant were obtained. The present studies may provide a way to analyze the biological safety of PMT on human health.(3)A simple, rapid and sensitive quantitative detection method of clinical medicine FAR was developed based on MWCNT-NH2]-IL/GCE. The oxidation current of FAR at MWCNT-IL/GCE was an adsorption-controlled and totally irreversible electrode reaction. The electron transfer number is around 2. Under the optimum conditions, this fabricated electrode exhibited good relationships with FAR concentration range from 5.6×10-7 to 1.6×10-4 mol/L and the detection limit was 3.1×10-8 mol/L(S/N=3). The fabricated electrode has been successfully applied to the determination of FAR in urine samples with satisfied results.The binding of FAR with HSA was investigated by the electrochemical and fluorescence spectrum analysis methods. It is important for us to insight into the pharmacokinectics of FAR. The results indicated that the number of binding site between FAR and HSA was 1 and binding constant KA=8.71×105 L/mol。... |
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