Microscopic Interface Between Two Immiscible Electrolytes: A Parallelism to an Ultramicroelectrode

Abstract

Current-potential response of a small interface formed between two immiscible solutions of electrolytes is examined. The diameter of the contact area made in a thin glass wall separating two solvents is approximately 130 μm. Ion transport across the nitrobenzene-water interface is studied by addition of probe semi-hydrophobic ions such as tetramethylammonium, tetraethylammonium, picrate, choline and dodecylsulfate to either aqueous or nonaqueous phase. The voltammetric behavior observed with the microinterface generally resembles that of a solid microelectrode of a similar radius. The contribution of ohmic drop becomes less significant with decrease of the interface area. This phenomenon permits voltammetric and amperometric measurements without using a potentiostat, and the solvent resistance is of a lesser problem.     

Etilefrine Plastic Membrane Electrodes Based on Individual and Mixed Ion-exchangers of Etilefrinium Phosphotungstate and Tetraphenylborate.

Abstract

Etilefrine hydrochloride (EfCl) selective PVC membrane electrodes based on Etilefrinium phosphotungstate (I), Etilefrinium tetraphenylborate (II) and a mixture of both (III) were prepared, The electrodes exhibited near Nernstian response over the concentration ranges 5.0 × 10^?6 - 1.0 × 10^?1, 6.3 × 10^?6 - 1.0 × 10^?1 and 6.3 × 10^?5 - 1.0 × 10^?1 M EfCl for electrodes I, II and III, respectively. The working pH ranges of electrodes I, II and III were 10 - 8.0, 10 - 7.5 and 10 - 7.5 and their isothermal coefficients were 0.00150, 0.00088 and 0.00072 V/°C, respectively. The electrodes showed good selectivity to EfCl with respect to many inorganic cations, sugars and amino acids. The standard additions method was used to determine EfCl in pure solutions and in pharmaceutical preparations.     

Flow-Injection Analysis of Chloride in Milk with a Dialyzer and a Coated Tubular Inorganic Chloride-Selective Electrode

Abstract

A rapid and reliable automated procedure for the direct measurement of the chloride content in milk is described. The method is based on the principles of the flow-injection technique; a dialyzer is used to eliminate interferences and the dialyzed chloride is measured with a coated tubular chloride-selective electrode. With this system potential change caused by the interference of casein is obviated, giving a stable baseline. Results obtained for chloride in milk at a sampling rate of 120 samples per hour compared well with data obtained by the standard Volhard titration method. With 30-μl samples a working range of 250–5000 mg/1 chloride is covered with a coefficient of variation of better than 0.50%.     

Minimizing Activity and Liquid Junction Errors In Direct Potentiometry By Using the Optimal Standard Solution

Abstract

In quantitative analysis by direct potentioroetry. e.g. when using ion-selective electrodes, situations arise where corrections appear necessary to account Tor activity coefficient and liquid junction potential effects. It is shown here that one can select an optimal composition for the standard or reference solution and thereby achieve two goals simultaneously: to reduce the error terms to a minimum and to eliminate the necessity of any corrective calculations.     

Potentiometric Determination of Sibutramine Using Batch and Flow Injection Analysis

Sibutramine (SBT⁺) ion-selective electrode (ISE) was constructed using poly(vinyl chloride) matrix membrane containing sibutramine–phosphotungstate (SBT–PTA) plasticized with dioctyl phthalate. The electrode exhibits Nernstian response of 59.54 mV/ concentration decade over the concentration range 1.0 × 10^?5 to 1.0 × 10^?2 M and detection limit of 7.94 × 10^?6 M. The electrode was fully characterized in terms of its composition, response time, life span, pH, selectivity, and temperature and was then applied to the potentiometric determination of SBT in its pure bulk and pharmaceutical formulations under batch and flow injection conditions and for the in vitro testing of the dissolution profile of SBT capsules.     

石墨烯及其复合材料在锂离子电池中的应用

石墨烯是一种单原子层厚度的石墨材料,具有独特的二维结构和优异的电学、力学以及热学性能。同时它也是一种具有良好应用前景的锂离子电池电极材料。电极材料的微观结构对其性能有很大影响,利用石墨烯获得具有特殊形貌和微观结构的电极材料,能有效改善材料的各项电化学性能。本文综述了石墨烯及其复合材料在锂离子电池中的应用研究进展。在负极复合材料中,石墨烯不仅可以缓冲材料在充放电过程中的体积效应,还可以形成导电网络提升复合材料的导电性能,提高材料的倍率性能和循环寿命。通过优化复合材料的微观结构,例如夹层结构或石墨烯片层包覆结构,可进一步提高材料的电化学性能。在正极复合材料中,石墨烯形成的连续三维导电网络可有效提高复合材料的电子及离子传输能力。此外,相比于传统导电添加剂,石墨烯导电剂的优势在于能用较少的添加量,达到更加优异的电化学性能。最后对石墨烯复合材料的研究前景进行了展望。     

Sb在Pt(100),Pt(110),Pt(111)及Pt(320)上不可逆吸附的电化学特性

研究了Sb在Pt(1 0 0 ) ,Pt(1 1 0 ) ,Pt(1 1 1 )和Pt(32 0 )单晶面上不可逆吸附的电化学特性 .发现当扫描电位的上限Eu≤ 0 .45V时 ,Sbad可以稳定地吸附在Pt(1 0 0 ) ,Pt(1 1 0 )和Pt(1 1 1 )表面 ,而Sbad在Pt(32 0 )表面稳定的电位较低 ,为Eu≤ 0 .40V .从饱和吸附Sb的铂单晶电极出发 ,通过改变电位扫描上限Eu 和电位扫描圈数可以获得不同Sb覆盖度 (θSb)的电极 .根据Sb和H在铂单晶电极表面共吸附的定量数据 ,对Sb在不同铂单晶面上饱和吸附的模型进行了初步探讨 .     

New Macrocycles Containing the Azoxy Subunit and Their Properties

Abstract

A new macroring closure reaction leading to crown-like macrocycles containing the azoxy group as a new macroring subunit has been introduced. The possibility of complex formation with cations has been examined by studying these compounds in membrane ion-selective electrodes.     

聚中性红膜修饰电极测定痕量NO2^—的研究

研究了聚中性红膜修饰电极对ＮＯ－２的催化氧化性能，建立了测定ＮＯ－２的新方法。ＮＯ－２的浓度在２．０×１０－６～５．０×１０－３ｍｏｌ／Ｌ范围内与催化氧化峰电流呈良好的线性关系，检测限为６．０×１０－７ｍｏｌ／Ｌ。若利用计时电流法分析，检测限可达８．０×１０－８ｍｏｌ／Ｌ。     

A study of bismuth-film electrodes for the detection of trace metals by anodic stripping voltammetry and their application to the determination of Pb and Zn in tapwater and human hair

This work reports the simultaneous determination of Cd(II), Pb(II) and Zn(II) at the low μg l⁻¹ concentration levels by square wave anodic stripping voltammetry (SWASV) on a bismuth-film electrode (BFE) plated in situ. The metal ions and bismuth were simultaneously deposited by reduction at −1.4 V on a rotating glassy carbon disk electrode. Then, the preconcentrated metals were oxidised by scanning the potential of the electrode from −1.4 to 0 V using a square-wave waveform. The stripping current arising from the oxidation of each metal was related to the concentration of each metal in the sample. The parameters for the simultaneous determination of the three metals were investigated with the view to apply this type of voltammetric sensor to real samples containing low concentrations of metals. Using the selected conditions, the limits of detection were 0.2 μg l⁻¹ for Cd and for Pb and 0.7 μg l⁻¹ for Zn at a preconcentration time of 10 min. Finally, BFE's were successfully applied to the determination of Pb and Zn in tapwater and human hair and the results were in satisfactory statistical agreement with atomic absorption spectroscopy (AAS).