| Phenol derivatives are widely used in the chemical industry, and some of the biological active compounds in a variety of beverages are beneficial to the health of human body. But at the same time, phenol is the main toxic environmental pollutants, the detection of such substances has become a research hotspot. However, most phenolic compounds have many isomers, due to the structural similarity and similar physical and chemical properties between these isomers, it is easy to appear at the same time in the production and application, so it is easy to bring trouble to the production process. Therefore, it is necessary to use some method to separate and detect it.Electrochemical analysis has become one of the hot topics in the field of analysis. In this paper, the carbon nanotube modified glassy carbon electrode and its preparation method and application are briefly introduced. The modified electrode is used as the working electrode, by combining with a three electrodesystem, cyclic votammetry, linear sweep voltammetry and differential pulse voltammetry were used to the simultaneous determination of methoxyphenol isomers and chlorophenol isomers, then satisfactory results were achieved. The main research contents are as follows:1?Pretreatment of electrode and preparation of multi-wall carbon nanotube modified glassy carbon electrode. The new glassy carbon electrode was polished smooth in turn on 3000 and 5000 mesh metallographic sandpapers, then polished to mirror with Al2O3 powder, followed by ultrasonication in ethanol and distilled water to clean, and then activated by cyclic voltammetry in sulfuric acid solution. Above steps repeated until the standard reversible cyclic voltammograms of ferricyanide solution was obtained, finally clean and dry the glassy carbon electrode for use. In order to remove impurities and increase the solubility of carbon nanotubes in solution, the carbon nanotubes were treated in the mixed acid of concentrated sulfuric acid and concentrated nitric acid.Homogeneous dispersion of the liquid was obtained by the ultrasonic dispersion of carbon nanotubes in Nafion(5%)-ethanol solution. The stable suspension is coated on the surface of the treated glass carbon electrode, until it is naturally dried, the carbon nanotube modified glassy carbon electrode is prepared.2?A cyclic voltammetry method was established for the simultaneous determination of three isomers of methoxy phenol. In a three electrode system,the carbon nanotube modified glassy carbon electrode was used as working electrode, Pt electrode as auxiliary electrode and a saturated calomel electrode asthe reference, the simultaneous determination of the three isomers of methoxy phenol was achieved combined with cyclic voltammetry. In a 0.1mol/L pH 6.0Na H2PO4-Na2HPO4 buffer solution, the optimal dispersion of the liquid was11?L, and the scanning rate was 100mV/s, simultaneous determination of three isomers of methyl phenol, an oxidation peak appeared on the first lap of the scanning curve of them. The peak potencials of o-methylphenol,m-methylphenol and p-methylphenol were 0.47 V, 0.55 V and 0.74 V,respectively. The oxidation peak current was found to have a linear relationship with the concentration of 30~110?mol/L and the detection limits were1.50×10-5mol/L,1.65×10-5mol/L and 2.94×10-5mol/L. The modified electrode combined with the excellent characteristics of carbon nanotubes, which has high sensitivity and selectivity in the detection of three kinds of phenol isomers, can be used to simulate the simultaneous determination of three substances in water samples.3?A differential pulse voltammetry method was established for the simultaneous determination of o-chlorophenol and m-chlorophenol,p-chlorophenol and m-chlorophenol. The modified electrode was used as working electrode, a saturated calomel electrode as the reference electrode and Pt electrode as auxiliary electrode, with cyclic voltammetry, the electrochemical behavior of three isomers of methylphenol on the carbon nanotube modified glassy carbon electrode was investigated, and the reaction mechanisms of the three isomers on the electrode were discussed. Then the simultaneousdetermination of o-CP and m-CP,p-CP and m-CP was realized by differential pulse voltammetry. By optimizing the experimental conditions, in a 0.1mol/L pH6.0 Na H2PO4-Na2HPO4 buffer solution, the optimal dispersion of the liquid was10?L, and the scanning rate was 100mV/s, simultaneous determination of o-CP and m-CP by differencial pulse voltammetry, the peak potentials of o-CP and m-CP were 0.63 V and 0.71 V, respectively. The oxidation peak currents were found to have a linear relationship with the concentration of 30~110?mol/L and the detection limits were 1.2×10-5mol/L and 2.09×10-5mol/L. Similarly,simultaneous determination of p-CP and m-CP, the peak potentials of p-CP and m-CP were 0.60 V and 0.70 V, respectively. The oxidation peak currents were found to have a linear relationship with the concentration of 30~110?mol/L and the detection limits were 1.94×10-5mol/L and 1.69×10-5mol/L. The modified electrode was applied to the determination of the simulated water samples and satisfactory results were obtained. |
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