恒电流库仑分析法测定维生素C等药物

以恒电流库仑分析法测定维生素C、安乃近、二巯丙醇等药物的含量,以永停终,最法指示库仑滴定终点,方法简便快速,相对误差为0．21％～0．28％,相对标准偏差（n=11）为0．027％～0．034％。     

Integrated coulometric sensor-actuator devices

Bi-directional transfer of data from the chemical to the electrical domain andvice versa is possible by the integration of a coulometric actuator electrode with a pH-sensitive ISFET.The device thus obtained can be operated in several modes, each offering specific advantages or new areas of application. This paper reviews the previously published applications and adds some original results. Besides a short introduction in the operational mechanism of the sensor-actuator device, the following applications are treated: acid or base concentration determination, carbon dioxide sensor, pH-static enzyme sensor, determination of diffusion coefficients, determination of buffer capacity, characterization of proteins and the application of alternative electrode materials.     

Determination Coulometrique de L'acide β Amino-Naphtylamido Thioglycolique (Thionalide)

Abstract

Mercury and silver were determined by precipitation from aqueous solution with β amino-naphthylamido thioglycolic acid (thionalid). The metallic thionalidate phases were separated, dissolved in ethanol and analyzed by coulometric titration of the thionalid with electrogenerated iodine.     

A Simple Coulometric Method for Determining Cu[II] and Cu[I] Contents in Various Solid Samples

Abstract

Determination of copper individual oxidation states (Cu[II] and Cu[I] in various solid samples is a rather difficult problem. Results are here presented to demonstrate that constant current coulametric techniques are useful to realize these determinations with good analytical characteristics. The analytical equivalence points obtained are based on the reversible electron transfer mechanisms: Cu[II] + 3 HC1 + 2 e CuCl^2? ₃ + 2H⁺ and : CuCl^2? ₃ +e = Cu(O) + 3 Cl^?, respectively, after quantitative dissolution in aqueous HC1 6 M. Cyclic voltammetric measurements with a carbon paste electrode are made to characterize the electron transfers involved and to investigate the analytical utility of the technique in various media. Analytical determinations are given, e.g., in the analysis of the CuO/Cu₂ O content of various samples.     

Determination of the purity of potassium iodate by constant-current coulometry

This paper describes a method of determining the purity of potassium iodate by constant-current coulometry. The determination can be divided into two steps. First, a Na₂S₂O₃ solution is prepared and its reductive value is determined. Second, the purity value of an oxidimetric quantity of potassium iodate is determined. This paper discusses the conditions of the reaction process and evaluates type A and B standard uncertainty of this method. The expanded relative uncertainty of this method is 0.02% (k=2). Received: 15 June 2000 Accepted: 27 December 2001     

Thermal analysis of transition metal and rare earth oxide system-gas interactions by a solid electrolyte-based coulometric technique

The oxidation-reduction behaviour of transition metal and rare earth oxide systems in oxygen potential controlled atmospheres was investigated by means of a solid electrolyte-based coulometric technique (SEC) in carrier gas mode to obtain information concerning the extent of oxygen stoichiometry, thep-T-x diagram of any mixed oxide phase, the kinetics of the oxygen exchange and the phase transitions.The direct coupling of SEC and electrical conductivity measurements provides further information about the relationship between oxygen deficiency and conductivity, especially as concerns the oxygen mobility and the transition from ionic to mixed ionic/electronic conductivity in any system.In the fluorite-type phases PrO_2–x, Ce_0.8Pr_0.2O_y–x and Ce_0.8Sr_0.08Pr_0.12O_y–x, the higher oxidation state of Pr is stabilized and the electrical conductivity increases in this sequence. The perovskite-type phase Sr_1–yCe_yFeO_3–x, shows transitions and a second phase reflected in the temperature-programmed spectrum of this substance. The electrical conductivity of Sr_0.9Ce_0.1FeO_3–x changes fromn-type top-type with increasing oxygen pressure.     

Electrochemical and microfabrication strategies for remotely operated smart chemical sensors: Application of anodic stripping coulometry to calibration-free measurements of copper and mercury

Remote unattended sensor networks are increasingly sought after to monitor the drinking water distribution grid, industrial wastewater effluents, and even rivers and lakes. One of the biggest challenges for application of such sensors is the issue of in-field device calibration. With this challenge in mind, we report here the use of anodic stripping coulometry (ASC) as the basis of a calibration-free micro-fabricated electrochemical sensor (CF-MES) for heavy metal determinations. The sensor platform consisted of a photo-lithographically patterned gold working electrode on SiO₂ substrate, which was housed within a custom stopped-flow thin-layer cell, with a total volume of 2–4 μL. The behavior of this platform was characterized by fluorescent particle microscopy and electrochemical studies utilizing Fe(CN)₆^3−/4− as a model analyte. The average charge obtained for oxidation of 500 μM ferrocyanide after 60 s over a 10 month period was 176 μC, corresponding to a volume of 3.65 μL (RSD = 2.4%). The response of the platform to copper concentrations ranging from 50 to 7500 ppb was evaluated, and the ASC results showed a linear dependence of charge on copper concentrations with excellent reproducibility (RSD ≤ 2.5%) and accuracy for most concentrations (≤5–10% error). The platform was also used to determine copper and mercury mixtures, where the total metallic content was measurable with excellent reproducibility (RSD ≤ 4%) and accuracy (≤6% error).     

The electrochemical behaviour of tris(N,N-disubstituted dithiocarbamato) complexes of ruthenium(III) in dimethylsulphoxide

The reduction at the mercury electrode of a series of ruthenium(III) dithiocarbamates in dimethylsulphoxide (DMSO) has been investigated using D.C. A.C. polarography, chronoamperometry, coulometry (controlled potential electrolysis) and cyclic voltammetry. Tris(N,N-disubstituted dithiocarbamato) complexes of ruthenium exhibit two one-electron polarographic waves in the potential range 0.00 to 2.20 volt relative to Ag/AgClO₄ (DMSO) reference electrode. The first reduction, at approximately — 0.950 volt, is quasi-reversible. The [Ru(II) (dAdtc)₃]⁻ complexes resulting from this reduction are susceptible to dissociation, releasing the free dialkyldithiocarbamate anion.     

非水库仑滴定法测定天然水体中溶解的无机碳

介绍用非水库仑滴定法测定天然水体中溶解的无机碳，对非水库仑滴定方法的关键技术－非水电解液进行了组分选择及优化，并对实验条件进行了优化。用该方法对碳酸钠标准溶液进行测定，测定结果的相对标准偏差为0.18%，测定值与理论值的平均相对误差为0.48%，表明该方法具有较高的精密度与准确度。