| AbstractPolarographic catalytic wave consists of two main variations, the parallel catalytic wave and the catalytic hydrogen wave. The catalytic hydrogen wave is ascribed to the fact that certain substances containing nitrogen or sulfur can diminish the hydrogen overvoltage and accelerate hydrogen ion discharge at more positive potential on the cathode. As for the parallel catalytic wave, it is attributed to the regeneration of the electroactive reactant via oxidation reaction of the reduction intermediate product of the reactant. The mechanisms of the two kinds of polarographic catalytic wave are totally different. Study of the catalytic wave has been mainly focused on the catalytic hydrogen wave of protein, and other kind of catalytic wave was rarely reported. Thus there is a big field for research work in study of the polarographic catalytic wave of organic compound. It is of great significance for electroanalytical chemistry, biology and pharmacological researches.In this thesis, parallel catalytic waves of berberine and hesperidin were observed and studied; otherwise, A new-type catalytic wave, which is named as parallel catalytic hydrogen wave, is discovered. Anionic surfactant linear alkylbenzene sulfonic sodium is taken as the example to discuss its mechanism.This thesis consists of four parts:PartⅠ. The achievement on electrochemistry of flavonoids was reviewed with 19 references. The achievement on electrochemistry of anionic surfactant was reviewed with 44 references. PartⅡ. For the first time, polarographic catalytic wave of berberine in the presence of H2O2 was studied in aqueous and DMF/H2O mixture solutions by linear-potential scan polarography, cyclic voltammetry and controlled-potential coulometry. Experiments showed that the reduction of the C=N bond of berberine was two successive one-electron reduction processes. An intermediate free radical was involved. When H2O2 as oxidant was present, berberine as catalyst was regenerated through that H2O2 oxidized the free radical to the original C=N bond, producing a polarographic catalytic wave of berberine itself.Part Ⅲ. A method for the determination of berberine was proposed based on its polarographic catalytic wave in the presence of H2O2. The experiment condition was optimised. In 8.0×10-2 mol l-1 Na2B4O7(Na2CO3 (pH9.4±0.4)(4.0×10-3 mol l-1 H2O2 base solution, the first-order derivative peak current of the catalytic wave was proportional to the berberine concentration in the range of 1.0×10-8～3.0×10-7 mol l-1. The sensitivity of the catalytic wave was 25 times higher than that of the corresponding reduction wave.Part Ⅳ. The mechanism of a polarographic catalytic wave of hesperidin in the presence of H2O2 was studied. Based on this, a new method for the determination of hesperidin was proposed. Linear-potential scan polarography, cyclic voltammetry, etc. were used in the present paper. The C=O bond of hesperidin at the C4 position firstly undergone a 1e, 1H+ reduction to form a intermediate free radical, and then further reduction in 1e, 1H+ process, being simultaneous with the dimerization reaction. When oxidant H2O2 existed, H2O2 and its reduction product ?OH could oxidize the free radical to the original C=O bond, interrupting its further reduction and dimerization process, producing a polarographic catalytic wave. In 0.12 mol l-1 HAc-0.40 mol l-1 NaAc(pH 5.3)-1.0×10-2 mol l-1 H2O2 buffer solution, first-order derivative peak current of the catalytic wave was proportional to hesperidin concentration in the range of 1.0×10-7～1.8×10-6 mol l-1. The catalytic wave has high sensitivity and can be used for application purpose. Part Ⅴ. A method for the determination of hesperidin was proposed based on its polarographic catalytic wave in the presence of KIO3. In 0.55 mol l-1 HAc～0.01 mol l-1 NaAc(pH=4.00(0.05)～1.0×10-3 mol l-1 KIO3 supporting electrolyte, the sensitivity of the catalytic wave was one order of magnitude higher than that of the corresponding reduction wave. The first-order peak current of the... |
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