Zero Streaming Potential Method, Based On The Potential Of The Conductive Polymer Film Sensing Induction

This thesis involves two parts:Part one Documents reviewElectrochemical analytical methods had been widely used to determination the biological molecules,inorganic ions,and so on due to their high selectivity and simple instrumentation.In recently years,chemically modified electrodes(CMEs) are an active area of electrochemical analytical research,and exploit a new field for the application in electroanalytical chemistry.While,the development of conducting polymers have bring new energy for CMEs.So,how connecting the special physical and chemical properties of conducting polymers to CMEs have attracted more attention.In this review,the application of potentiometry,voltammetry and conducting polymers modified electrodes were reviewed.Part two Research reportsIn this thesis,the poly(methyl red)(PMR) film/pencil graphite and poly(L-cysteine) (PLC) film/pencil graphite electrodes were prepared through cyclic voltammetry,then the electropolymerization process of PMR and PLC were studied.Meanwhile,a novel electrochemical approach,named as zero current potentiometry,has been proposed for studying the pH response of PMR film and the Cu(Ⅱ) response of poly(L-cysteine) film.In addition,the electrochemical oxidation of ambroxol(AMB) and the determination by the enhancement effect of anion surfactant sodium dodecyl sulfate(SDS) toward the oxidation peak of AMB were studied at carbon paste electrode(CPE).The concrete contents are described as follows:Chapter one pH Sensing of Poly(Methyl Red) Film with Zero Current PotentiometryA novel electrochemical approach,named as zero current potentiometry,has been proposed for studying the pH response of an azo-dye polymer film-poly(methyl red) film on pencil graphite through electro-polymerization,poly(methyl red) film/pencil graphite was in series between the terminal joints of working electrode and counter electrode,and linear sweep potential was imposed on the working electrode,then the curve I-E of current versus potential was recorded,and the potential point of I-E curves at the resulting zero currentzero current potential E_zcp was chosen as a measurement paramerer,finally the relationshiop of the zero current potential E_zcp and the pH was discussed.With the proposed zero current potentiometry,the zero current potential E_zcp shows linear to pH value in the wide range of pH 1.81～11.88 with the average slope-28 mV/pH.Comparing with classical open circuit potentiometry,the proposed approach presents the excellent performance of fast response, high stability and good repeatability under the condition of either high pH or low pH.Chapter two Cu(Ⅰ) Ion Sensing of Poly(L-cysteine) Film with Zero Current PotentiometryThe zero current potentiometry has been proposed for studying the Cu(Ⅱ) response of poly (L-cysteine) film on pencil graphite(PLC film/pencil graphite) through electro-polymerization. The Cu²⁺ ions was reduced to Cu⁺ ions when linear sweep potential was applied,then the interface potential was generated from the complexation between Cu⁺ ions and sulfhydryl, amino and carboxyl groups of PLC film surface.Owing to effect of interface potential between PLC film and the solution,I-E curves shifted along E-axis with variations of Cu²⁺ ions concentrations.Zero current potential E_zcp of I-E curves was measured and shows linear to log C_Cu²⁺ in the wide range of 3.0×10^-6～4.0×10^-5 mol·L^-1 with the slope 59 mV/pCu²⁺.The proposed approach presents the excellent performance of good sensitivety,high stability and good repeatability.Chapter three Electrochemical Oxidation of Ambroxol and its Voitammetric Determination Based on the Enhancement of Sodium Dodecyl SulfateThe electrochemical oxidation of ambroxol(AMB) at carbon paste electrode(CPE) was studied.It was confirmed that the primary amine group in aniline parent of AMB was oxidized to be a quinone imine derivative of AMB through a two-electron and two-proton transfer.Then the quinone imine derivative of AMB was subsequently hydrolyzed to a p-benzoquinone derivative of AMB.In addition,it was observed that only anionic surfactant sodium dodecyl sulfate(SDS) markedly enhanced voltammetric response of AMB.With the enhancement,a single-sweep voltammetric method was proposed for the determination of AMB.In 0.1 mol·L^-1 HAc-NaAc(pH 5.0) buffer containing 3.0×10^-4 mol·L^-1 SDS,the second-order derivative oxidation peak current at 0.93 V showed a linear relationship with AMB concentration in the range of 3.0×10^-8～4.0×10^-7 mol·L^-1,the limit of detection was 5.4×10^-9 mol·L^-1.As compared with the reported voltammetric methods previously,the sensitivity of the proposed method was improved in at last one order of magnitude,and the oxidation peak potential of AMB was reduced by about 0.10 V and more.