Electrochemical characterization of polyaniline films formed on an ITO substrate during the cathodic reduction of dioxygen

Polyaniline films are fabricated on an electrode of mixed indium and tin oxides (ITO) during the cathodic reduction of dioxygen in an aniline-containing solution. Their electrochemical properties are characterized by methods of cyclic voltammetry, faradaic impedance, and chronoamperometry. A quantitative treatment of results that are obtained by the last two methods leads to results that well agree with each other and makes it possible to reliably determine basic charge transport parameters.     

阳极溶出伏安法中表面活性剂增敏机理探讨

本文探讨了表面活性剂在镉的阳极溶出伏安法中的增敏机理，认为表面活性剂可使训金属的水合子或其它络离子发生部分解离，既增加了溶液中电活性络离子的深度，又使离子的扩散速度加快，从而产生增敏作用。     

Comparison Of Analytical Techniques For The Determination Of Trace Elements In Rain Water

Abstract

Summary-Two methods for the determination of cadmium, copper and lead in EPA reference precipitation sample, corresponding to 1987, 1988, 1989 and 1990 BAPMoN Intercomparison Program, have been compared: graphite furnace atomic absorption spectroscopy (GFAAS) and anodic stripping voltametry (ASV). A relatively good agreement was found between the two techniques and with the reference values. The results for the analysis of Cl and F by spectrophotometry, Ca, Mg, Na, K and Zn by AAS, and Fe, Mn, Cu, Ni, Pb and Cd by GFAAS in the same sample, corresponding to 1988 and 1989, showed good agreement with the stated values. The results of Easter Island rain waters for the years 1990 and 1991 are presented.     

TiO2-石墨烯-Nafion复合膜修饰玻碳电极同时测定多巴胺和尿酸

利用在玻碳电极上修饰了TiO2-石墨烯-Nafion复合膜制得的修饰电极进行多巴胺(DA)和尿酸(UA)的同时测定。用循环伏安法(CV)和差分脉冲伏安法(DPV)研究了该修饰电极的电化学行为。在pH为7.0的磷酸盐缓冲液(PBS)中,修饰电极对于DA和UA的电化学氧化具有良好的电催化性能。DA和UA的氧化峰电流分别在2～120和60～300μmol/L浓度范围内呈良好的线性关系,检出限分别为0.066和0.102μmol/L。实验结果表明,TiO2-石墨烯-Nafion复合膜修饰电极显著提高了检测的灵敏度,并表现出良好的选择性和重现性。     

Redox Behavior of Zearalenone in Various Solvents

The redox equilibriums involving zearalenone were studied by cyclic and differential pulse voltammetry on a glassy carbon electrode. The cyclic voltammograms of zearalenone in DMSO at a glassy carbon electrode in the potential range from ?600 to 1400 mV vs. the Ag/AgCl have two oxidation peaks and a reduction one. Zaralenone concentration may be determined by DPV at +1050 mV. The method was applied to the determination of zearalenone concentration in corn, barley, and maize. Studies performed in aqueous solution or in mixed solvents water-acetonitrile containing 1 M H₂SO₄ showed that the oxidation of ZEN with an aqueous solution of Ce(IV) at room temperature, in the dark, occurs with the destruction of ZEN molecule. Studies performed in aqueous solution or in mixed solvents water-acetonitrile containing 1 M H₂SO₄ showed that the oxidation of ZEN with an aqueous solution of Ce(IV) at room temperature, in the dark, occurs with the destruction of ZEN molecule.     

伏安法测量电阻的误差分析

本文给出伏安法测量电阻时，安培计内、外接法的定量选择公式，定量地描绘了使测量误差在允许范围所需要采取的具体措施。     

Cathodic adsorptive stripping voltammetric determination of uranium (VI) complexed with 2, 6-pyridinedicarboxylic acid

Uranium (VI) (U(VI)) forms a complex with dipicolinic acid (2, 6-pyridinedicarboxylic acid).This complex can be used for a highly sensitive and selective determination of uranium by adsorptive cathodic stripping voltammetry (ACSV) using a hanging mercury drop electrode (HMDE) as working electrode. Influence of effective parameters such as pH, concentration of ligand, accumulation potential and accumulation time on the sensitivity and selectivity were studied. The detection limit (3σ of the blank value) obtained under the optimal experimental conditions is 0.27 × 10⁻⁹ M after 150 s of the accumulation time. The peak current is proportional to the concentration of U(VI) in the range of 1 × 10⁻⁹ to 1.2 × 10⁻⁷ M. The relative standard deviation of 2.5% at the 3.5 × 10⁻⁸ M level was obtained. The interference of some metal ions and anions were studied. The application of this method was tested in the determination of uranium in synthetic and natural water samples.     

New conducting pyrrole–thiophene co-polymer from an oligomer precursor: electrochemical characterisation

A new oligomer of N,N′-bis(2-pyrrolyl methylene)-3,4-dicyano-2,5-diaminothiophene possessing cyano-substituted thiophene and pyrrole residues linked together by azomethine groups was used for the electrochemical polymerisation of conducting films. The approach used for the oligomer design favours inter-chain interactions through hydrogen bonding and negative charge stability through the cyano substitute thiophene. The oligomer was successfully electropolymerised at 0.67 V vs Ag⁺/Ag from 0.1M tetrabutylammonium tetrafluoroborate (TBABF₄)/acetonitrile as a dark blue film on the surface of platinum electrodes. Cyclic voltammetry has been used to investigate the redox behaviour of the films. The electrically conducting polymer showed p-doping/neutralisation behaviour. The effect of different electrolytes such as TBABF₄, tetrabutylammonium perchlorate (TBAClO₄), lithium perchlorate (LiClO₄) and sodium perchlorate (NaClO₄) on the redox switching and the stability of the polymer films was investigated. Infrared and UV-vis spectra of oligomer and polymers are presented. The evolution of the film growing process is shown by UV-vis spectroscopy.