The Electrochemical Applications Of 8-Hydroxyquinoline Aluminum Complex Modified Carbon Paste Electrode

Chemically modified carbon paste electrode has very important applications in the fields of electrochemistry and electrochemical analysis. In this thesis, the modified carbon paste electrodes were compositd of graphite powder modified by 8-hydroxy quinolinealuminum complex and methyl silicone oil. The electrochemical catalytic behavior and electrochemical capacitors properties of potassium ferrocyanide and pyrogallol as probes on the modified carbon paste electrodes were studied by cyclic voltammetry.The potassium ferrocyanide shows a typical electrochemical catalytic behavior on 8-hydroxyquinoline-aluminum modified carbon paste electrodes. The 1:1 of coordination ratio of the complex(solution volume is 0.25 m L of 3 mmol/L 8-hydroxyquinoline and 0.75 m L of 1 mmol/L Al Cl3) was used in the modification of 1.0g of graphite powder,which can form a very complete film on the surface of graphite powder and show the best electrocatalytic property. The catalytic oxidation reaction of potassium ferrocyanide at the modified electrode is mainly controlled by diffusion, but on the unmodified electrode, the oxidation reaction is controlled by both of surface and diffusion.Pyrogallol on the modified carbon paste electrode also shows the electrochemical catalytic activity. Also on the 1:1 coordination ratio of 8-hydroxy quinoline aluminum complex modified carbon paste electrode shows the best to pyrogallol oxidation. Pyrogallol at the modified electrode shows surface adsorption phenomenon, with the catalytic oxidation process controlled by surface and diffusion. The electrochemical catalytic oxidation of pyrogallol on the electrode is related to its solid phase micro-extraction and liquid microextraction, and follows the secondary adsorption kinetics and thermodynamics with a Freundlich adsorption model. A cyclic voltammetric method was developed and used in determination of pyrogallol in tomatoes. In the recovery assay process, an influence of peroxidase in tomato was found.The capacitance property of 8-hydroxyquinoline-aluminum modified carbon paste electrode was also studied by cyclic voltammetry. It is found that the capacitance of the modified electrode increases 9 times apparently compared with the bare electrode. The modification of 8-hydroxyquinoline-aluminum complex with coordination ratio of 1:3 shows the best, which can be used as a new type of super capacitors. The capacity also affected by many other factors, including modifications dose and scan rate, sweep segments and so on.In order to evaluate the diffusion constance of pyrogallol in aqueous solution, the Pc mod 6.1software was used to establish a molecular model of pyrogallol in aqueous solution, and then the semiempirical quantum chemistry method of Winmopac7.1 software was used to calculate the molecular structure parameters. The multiple linear regression method in quantitative structure-activity relationship(QSAR) was used to study the relationship of diffusion coefficient with molecules quadrupole(μT), molecular volume(Vm), electron energy(Ee). And it shows the multi-linear relationship and predicts that the diffusion coefficient of pyrogallol is about(2.04 ± 0.14) × 10-6cm2/s. It provides a new idea and new method for predicting the diffusion coefficients of other phenolic compounds and other compounds in aqueous.