Response to high acidity and basicity at a platinum electrode in chronopotentiometry

A simple and rapid method is developed to determine the high acidity and the basicity of solutions by chronopotentiometry with a platinum working electrode. The acidity range from 5.0 mol/l H⁺ to 1.0 mol/l OH⁻ can be measured by the adjustment of deposition potential and time. The response mechanism to acidity and basicity has been explored. The transition potential plateau in chronopotentiograms is caused from the oxidation of hydrogen adsorbed on electrode surface.     

交流示波极谱法中if～E曲线的研究（Ⅱ）：if～E曲线的理论公式

提出利用i_f～E曲线代替常用的dE/dt～E曲线的新的交流示波极谱法,并研究了该法的基本理论,推导出i_f～E曲线的理论公式。     

The effect of zinc(II) and some chromium complexes on the constant current chronopotentiometry of insulin

The constant current chronopotentiometry (CCCP) of zinc-free insulin was examined and the effect of additions of zinc(II) or either of two chromium complexes to the zinc-free zinc was studied. The zinc free insulin gave a constant current chronopotentiometric (CCCP) response which indicated that the freeze drying process, which was part of its preparation, may have denatured the insulin. The addition of zinc(II) appeared to reverse this since the response following zinc additions was similar to that of native insulin. Of the two chromium complexes investigated for their influence on insulin electrochemistry tripicolinato chromium(III) had no effect on the CCCP response, trans-Diaquoethylenebis-(salicylideneiminato) chromium(III) had an indirect effect by appearing to restore the native conformation of the insulin following the apparent denaturation caused by the removal of zinc.     

Sensor–actuator system for dynamic chloride ion determination

Chloride is a crucial anion for various analytical applications from biological to environmental applications. In order to measure the chloride ion concentration, a measurement system is needed which can detect this concentration for prolonged times reliably. Chronopotentiometry is a technique which does not need a long term stable reference electrode and is therefore very suitable for prolonged ion concentration measurements. As the used electrode might be fouled by reaction products, this work focuses on a chronopotentiometric approach with a separated sensing electrode (sensor) and actuating electrode (actuator). Both actuation and sensor electrode are made of Ag/AgCl. A constant current is applied to the actuator and will start the reaction between Ag and Clˉ, while the resulting Clˉ ion concentration change is observed through the sensor, which is placed close to the actuator. The time it takes to locally deplete the Clˉ ions is called transition time. Experiments were performed to verify the feasibility of this approach. The performed experiments show that the sensor detects the local concentration changes resulting from the current applied to the actuator. A linear relation between the Clˉ ion concentration and the square root of the transition time was observed, just as was predicted by theory. The calibration curves for different chips showed that both a larger sensor and a larger distance between sensor and actuator resulted in a larger time delay between the transition time detected at the actuator and the sensor.     

Voltametric,Amperometric, and Chronopotentiometric Determination of Submicromolar Concentrations of Carboxin

New procedures for the determination of pesticide carboxin were developed using differential pulse voltammetry, HPLC with amperometric detection and chronopotentiometry at carbon paste electrode and reticulated vitreous carbon electrode, respectively. Developed procedures based on electrochemical oxidation of carboxin were successfully applied on the determination of carboxin in the model samples of drinking and river water. Limits of detection in samples of river water were in 10^?7 mol L^?1 concentration range for all procedures and electrodes used. All developed procedures proved to be sensitive, accurate and, due to the resistance of the electrode to the passivation, also simple to handle.     

季铵酚离子在水／硝基苯界面的转移

油/水界面上的电化学研究是近年来电化学研究中的一个新领域,对膜电化学的发展具有重要意义。目前研究油/水界面电化学中普遍使用循环伏安(CV)法和循环线扫电流计时电位(CLC)法。有关抗生素在油/水界面的转移已有报导,本文用CLC法和CV法对肌肉松弛剂季铵酚离子在水/硝基苯界面的转移行为进行了研究。 所用三碘季铵酚为中国科学院生物化学研究所生产的化学试剂,其他试剂及仪器均与前文相同     

双1:11镝的硅钼杂多酸的液/液界面电化学研究

用循环线性电流扫描计时电位法和循环伏安法研究了双1∶11镝的硅钼杂多酸阴离子在水／硝基苯界面的转移。在pH＝1．1～5．3时，转移离子为H9Dy（SiMo11O39）24－．根据循环伏安结果计算得转移离子的标准电位差和Gibbs转移自由能分别为0．102V和－39．5kJ•ml-1，并由循环线性电流扫描计时电位法计算了转移离子的有关动力学参数，H9Dy（SiMo11O39）24-在水／硝基苯界面的转移属准可逆转移．     

Electrocatalytic Determination of Histamine on a Nickel‐Film Glassy Carbon Electrode

The electrocatalysed oxidation of histamine on a thin film nickel electrode was investigated for the purpose of its chronopotentiometric determination. The oxidation mechanism implies complex and combined processes of histamine physical adsorption and consequent oxidation via joined oxidation potency of a constant current and electrochemically generated nickel‐oxihydroxide, which played a role of an electron transfer catalyst. Experimental parameters affecting the oxidation process, including type and concentration of supporting electrolyte, initial potential, oxidation current, temperature and concentration time, were optimised. Using a 240 s accumulation time, limit of detection and quantitation were 0.11 mg L^?1 and 0.29 mg L^?1 of histamine, respectively.     

Theoretical and Experimental Study of the Homogeneous Catalytic Oxidation of Nicotinamide Adenine Dinucleotide (NADH) at Spherical Gold Electrodes Using Linear Sweep Voltammetry and Chronopotentiometry

The homogeneous catalytic oxidation of coenzyme nicotinamide adenine dinucleotide (NADH) with dopamine at a thiolactic acid modified gold spherical electrode of radius 0.0128 cm has been studied in aqueous phosphate media (pH 7.0) using linear sweep voltammetry and chronopotentiometry with power time and exponential time currents. We have proved that, under the conditions of this study, the steady state is reached, in such a way that the expressions for the I?E and dI/dE?E responses are simplified and become independent of time and the electrochemical technique employed. Therefore, the experimental I?E and dI/dE?E curves obtained in chronopotentiometry and linear sweep voltammetry are practically superimposable and, from easy expressions for the peak parameters of the dI/dE?E curves deduced in this paper, values of the chemical and electrochemical rate constants have been obtained.