Research And Application Of Electrochemical Properties Of Several Kinds Of Natural Products

Electrochemical analysis has been widely applied in the field of analysis and detection due to its simple operates,high sensitivity and good selectivity.In this thesis the electrochemical behavior of several nature products was studied by electrochemical analysis to reveal the reaction mechanism.The reversibility of the reaction and reaction mechanism were obtained from the electrochemical data by the electrochemical theory and method,and the sensitivity and selectivity of the tested samples were improved through the modified electrode,then further made it applied to some drugs,toxic and harmful substances in the environment of medical and health.Therefore it is necessary to study the voltammetric properties on the natural products and their application as well as determination.(1)In the phosphate buffer solution with a pH value of 3.0,the electrochemical behavior of genistein was studied by cyclic voltammetry at carbon paste electrode(CPE),and to investigate the electrochemical reaction mechanism.The result showed that genistein produced two oxidation peaks at +1.14 V and + 0.746 V.The oxidation peak current of genistein was liner with its concentration in the range of 4.0 × 10-9 ~ 2.0 × 10-6mol/L and the detection limit was 2.5 × 10-9 mol/L.The relative standard deviation was 2.8% calculated after 6 times parallel determination on the solution concentration of 8.0 × 10-7 mol/L.The proposed method was applied to the research drug metabolism and found the recoveries were in the range of 96%~103%.(2)In the phosphate buffer solution with a pH value of 4.0,the interaction between genistein and human serum albumin(HSA)was investigated at carbon paste electrode(CPE)by cyclic voltammetry and square wave voltammetry.The study found that genistein could combine with HSA to generate a non-electric complexes with the binding number of 1 and the binding constant ? of 1.3 × 106 L/mol.With the addition of HSA into a genistein solution,the oxidation currents of genistein decreased proportionally to the HSA concentration from2.0 × 10-8 mol/L to 1.0 × 10-5 mol/L,and the detection limit was 1.0×10-8 mol/L.(3)The electrochemical behavior of alizarin cyanine green(ACG)and the catalytic effect of hydrazine toward it were studied by cyclic voltammetry at carbon paste electrode(CPE).In the phosphate buffer solution with a pH value of 6.0,ACG produced apair of two-electron and two-proton quasi-reversible redox peaks.The square wave oxidation peak current of ACG was liner with its concentration range from 2.0 × 10-8 to 8.0 × 10-7mol/L and the detection limit was 1.0 × 10-8 mol/L.In the phosphate buffer solution with a pH value of 8.0,reducing agent hydrazine had obvious catalytic effect to the oxidation of ACG.The square wave catalytic oxidation peak current of ACG was liner with its concentration range from 2.0 × 10-9 to 8.0 × 10-7 mol/L and the detection limit was 1.2 × 10-9mol/L.The relative standard deviation was 3.7% calculated by 8 times parallel determination of ACG.The proposed method was applied to the determination of ACG in dye wastewater and the recoveries were range from 97% to 102%.(4)The electrode modified by Ni(?)-ACG-CPE HSA been fabricated on the surface of carbon paste electrode(CPE)and the catalytic effect of hydrazine toward it in NaOH solution with the concentration of 0.1 mol/L were studied.The Ni(II)-ACG-CPE exhibited the characteristic of improved reversibility and enhanced current responses compared with CPE and it also showed good electrocatalytic activity toward the oxidation of hydrazine.The catalytic currents presented linear dependence on the concentration of hydrazine from 1×10-5mol/L to 1.6×10-4 mol/L by amperometry.Surface coverage ? and catalytic rate constantcatk were also determined.The electrode modified by hydrazine had the property of good stability and rapid response which can be used for the determination of hydrazine in industrial waste water,and the recoveries were in the range of 99.9% ~ 103.5%.(5)A new electrochemical analysis method named as zero-current potentiometry for studying the pH-response on an electrode which modified by urushiol.The experimental results showed that the sensor had a sensitive response to pH changes.So when the phosphate buffer solution with a pH value of 6.0 and in which the urushiol modification agent content was 1%,the concentration of Hg2+ in industrial waste water were detected by the modified electrodes.The result showed that the Ezcp of Hg2+ was liner with its concentration in the range of 4 × 10-6 ~ 2 × 10-5 mol/L and its detection limit was 4.6 × 10-6 mol/L.This method could be used to detect heavy metal ions in industrial wastewater and its recoveries were in the range of 97% ~ 101%.