表面活性剂在离子选择电极分析中的增敏作用

本文以涂丝Ag-Ag2S电极为指示电极,饱和甘汞电极和自制锑电极为参比电极,分别试验了加入阳离子、阴离子和非离子表面活性剂对电极灵敏度的影响。结果表明,加入非离子表面活性剂对电极响应无明显影响,但阴离子和阳离子表面活性剂可使电极灵敏度有较大提高;其中,十六烷基三甲基溴化铵(CTMAB)和十二烷基苯磺酸钠(SDBS)、十二烷基硫酸钠(SDS)对电极的增敏效果显著,可使电极响应线性范围下限扩大一个数量级左右,且电极响应时间缩短,稳定性提高。     

Rotating minidisk–disk electrodes

Rotating minidisk–disk electrode (RMDDE) was developed by replacing ring electrode of rotating ring–disk electrode (RRDE) with a minidisk electrode. Its applications were demonstrated by studying electrochemical reactions of ferricyanide and divalent copper. The replacement of ring electrode by minidisk electrode results in following advantages. First, the fabrication of RMDDE is easier than that of RRDE with the same electrode material. Second, there is more freedom in choosing electrode materials and sizes, since it is difficult to make thin ring electrodes of RRDE with fragile materials. Third, the replacement of ring electrode by minidisk electrode saves electrode materials, especially rare materials. Finally, the substitution of minidisk electrode for ring electrode allows using multiple minidisks for simultaneous monitoring of multiple components. Therefore, RMDDE is a promising generator–collector system, especially when special generator–collector systems are not commercially available, such as corrosion study and electrocatalysis study of new electrode materials.     

Fabrication of Pt nanoparticles-decorated CVD diamond electrode for biosensor applications

An electrochemical biosensor was developed using boron-doped diamond (BDD) as an electrode material. To enhance the electrical performance of the electrode, the BDD electrode was decorated with Pt-nanoparticles (Pt-NPs) by electrochemical deposition. Their morphology according to the applied potentials for the synthesis of Pt-NPs was characterized by SEM. To identify the performance of the electrode modified with Pt-NPs, glucose detection was used as a sample sensing process, and the results were compared with those of a gold electrode and a bare BDD electrode. The electrochemical characteristics of the modified electrode were examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The BDD electrode with the Pt-NPs showed higher sensitivity and a lower detection limit than the Au electrode and BDD electrode. The proposed biosensor based on the Pt-NPs decorated BDD electrode showed high sensitivity, a low detection limit, fast direct electron transfer and good stability.     

双盘工作电极参比电位采样快扫伏安方法

报道一种双铂盘工作电极、相应的毛细管参比电极和竖直式电化学池设计并用于快速循环伏安测量.双工作电极包括一个常规工作电极,一个辅助工作电极.后者在使用中接地,仅提供参比电位来控制工作电极的电位.参比毛细管尖端安设在接近辅助工作电极的位置上;用0.3mm直径Pt盘工作电极,在电位扫描速度高达10kV/s都可以得到类似于100%iR补偿的伏安曲线,而不必使用iR补偿电路.本文围绕高扫速伏安法中工作电极电位的准确控制问题做了一些初步的探讨.     

Parallel and serial dual electrode detectors for capillary electrophoresis

Application of parallel and serial dual electrode detectors for capillary electrophoresis was first described. In parallel dual electrode approach, two 100 μm-diameter Cu disks arranged side by side were used as the dual working electrode for the simultaneous determination of a mixture of carbohydrates and amino acids. In serial dual electrode approach, two working electrodes were arranged in a disk-ring manner for the simultaneous determination of both cysteine and cystine; the disk electrode was Hg/Au serving as the upstream electrode, the ring electrode was 5% CoPC carbon paste serving as the downstream electrode.     

Carbon Powder Based Films on Traditional Solid Electrodes as an Alternative to Disposable Electrodes

The covering of conventional solid electrode with a film using an ink containing a conductive powder and a polymer enables to broaden the potential window of the original solid electrode. A solid silver amalgam electrode covered with such a film exhibits a potential window from ?600 mV to +1400 mV vs. SCE reference electrode. The renewal of the film is fast and simple: the electrode can be simply wiped with a filter paper to remove the old film and immersed into an ink solution or 1–2 μL of this ink solution can be applied to the surface of the electrode with a micro dispenser to form a new film. Therefore, just the inexpensive film at the electrode surface is disposable and there is no need to dispose the whole, more expensive electrode. Moreover, when a suitable electrochemical pretreatment of the film electrode is applied, the same film can be used for reproducible measurements for several days.     

The mechanism of the electrogenerated chemiluminescence of luminol in aqueous alkaline solution

The mechanism of the electrogenerated chemiluminescence of luminol in aqueous alkaline solution based on the rotating ring—disc electrode system is discussed. The disc electrode is maintained at a negative potential and the ring electrode at a symmetrically changing double-step potential. Hydrogen peroxide generated at the disc electrode by the reduction of oxygen is immediately transported to the ring electrode because of electrode rotation. Hydrogen peroxide and luminol are oxidized at the ring electrode during the positive pulse of the double-step potential. These oxidation processes generate a superoxide radical and a luminol radical as intermediates. The luminol radical reacts with the superoxide radical (or oxygen) emitting light.     

A study of electrodes used in controlled-potential electrolysis of metal ions

Various electrodes used in controlled-potential electrolysis of metal ions are discussed: (1) a double-junction saturated calomel reference electrode with sodium formate as bridge electrolyte; (2) an auxiliary electrode made by winding platinum wire on a Teflon cylinder; (3) a working electrode made of tantalum gauze. The advantages of the tantalum electrode over a platinum electrode are that the hydrogen overpotential is higher, and the tantalum electrode need not be precoated with copper before deposition of metals such as Bi, Zn and Sn, which tend to form alloys with platinum. The electrode needs pretreatment before use, but this takes only 4 min or less.     

Abrasive immobilization of carbon nanotubes on a basal plane pyrolytic graphite electrode: application to the detection of epinephrine

The performance of a basal plane pyrolytic graphite (bppg) electrode modified with carbon nanotubes is described. Abrasive immobilization of multiwall carbon nanotubes on a bppg electrode was achieved by gently rubbing the electrode surface on a filter paper supporting carbon nanotubes. The resulting electrode showed excellent mediation of epinephrine oxidation: a decrease in the overvoltage of the epinephrine electro-oxidation (200-500 mV) was observed as well as a dramatic increase in the peak current (4 times) compared to that seen at a bare bppg electrode. The oxidation peaks of epinephrine and ascorbic acid which overlap on bare bppg electrode were separated successfully (by ca. 220 mV) at the surface of the modified bppg electrode. The modified electrode showed good stability in comparison to most modified carbon nanotubes electrodes prepared by alternative methods.     

Studies of copper(II) sulphide ion-selective electrodes

Changes in liquid junction potentials in copper(II) solutions were measured when different reference electrodes were used. The slope and intercept of a calibration curve for a copper-selective electrode will depend on the selection of reference electrode. The condition of the electrode surface of an Orion copper-selective electrode was studied microscopically and the influence of redox potential on stability of the electrode against corrosion is discussed. Oxidizing solutions will produce pits at dislocations in the material and there will be a mixed electrode potential. The slope, stability, and speed of response are much lower when the surface contains pits. Diamond-polishing was shown to improve the electrode significantly.     

生姜粉末组织过氧化氢传感器的研究

用生姜粉末组织作生物催化材料与氧电极结合制姜粉组织过氧化氢传感器，５．０×１０＾－５－２．０×１０＾－３ｍｏｌ／Ｌ范围内响应信号与过氧化氢浓度成正比，并与新鲜生姜组织电极和过氧化氢酶电极作对比，结果表明姜粉组织电极性能优良，且酶源容易获得和保存。     

A Concentric Ring Electrode for a Wall‐jet Cell in a Microfluidic Device

A concentric ring array electrode that amplifies the current signal without redox cycling has been developed for highly sensitive electrochemical detection at a single potential in a microfluidic platform. Herein, the effect of ring‐electrode width on the current and current density was examined. A ring‐array electrode with widths that decrease from the inner to the outer ring was shown to exhibit the highest sensitivity. This electrode delivered a current density that was approximately 50 % higher than that of a conventionally used disc electrode. We used numerical simulations to further optimize this type of array electrode, which led to a limit of detection for catechol of 6.2 nmol/L. This ring array electrode has great potential for use in a variety of applications because it can be used to detect irreversible targets with a simple apparatus at a single potential and requires no electrode modification to achieve high sensitivity.     

血红素LB膜的电化学行为

采用循环伏安法研究了血红素与脑磷脂混合Y型LB（Langmuir-Blodgett）膜在玻碳电极上的电化学行为，结果表明血红素LB膜有良好的电化学活性，在0．1mol/L KCl溶液中有一对氧化还原峰（－0．42V／－0．30V）；将血红素LB膜转移到玻碳电极表面得到的血红素LB膜修饰电极（heme LB-GC）对溶液中溶解氧的电化学还原有良好的催化作用，其催化还原过程具有不可逆电荷传递特性。     

Immobilization of glucose oxidase on carbon paper electrodes modified with conducting polymer and its application to a glucose fuel cell

A carbon paper electrode was modified with the conducting copolymer of 3-methylthiopene and thiophene-3-acetic acid prepared electrochemically on the electrode, and an enzyme electrode was fabricated by covalent immobilization of glucose oxidase on the modified electrode. The modification with the conducting copolymer increased the surface area of the electrode and the amount of the immobilized enzyme. As a result, the enzyme electrode showed a high catalytic activity. Moreover, it was found that the increased surface area led to a high rate of electron transfer reaction between the electrode and p-benzoquinone employed as an electron mediator. The enzyme electrode fabricated with the modified carbon paper gave a larger glucose oxidation current than that fabricated with the bare one. In addition, the glucose oxidation current was found to increase with increasing content of the conducting copolymer in the modified carbon paper. Corresponding to the large glucose oxidation current, high performance was confirmed for the glucose fuel cell constructed with the enzyme electrode based on the modified carbon paper.     

Establishment of a Hydrogen Scale in 80 Mass % Propylene Carbonate + <Emphasis Type="Italic">p</Emphasis>-Xylene Medium

Details of the standardization of the reference electrode Hg/HgCl_2(s) versus the SHE by a potentiometric method using two acids (viz., perchloric and 2,5-dichlorobenzene-sulfonic acids) in 80 mass % propylene carbonate (PC) + p-xylene (PX), are presented. Using this reference electrode, the standard electrode potential of the quinhydrone electrode was determined in this medium. The reference electrode potential and the standard electrode potential of the quinhydrone electrode were found to be (0.277±0.003) and (0.760±0.003) V versus SHE in 80 mass % PC + PX at 25 °C, respectively. The voltammetric behavior of the quinhydrone system in this medium was investigated at a micro platinum electrode against a non-aqueous double-junction Ag/AgCl reference electrode. The standard electrode potential of the quinhydrone system was also calculated using voltammetric and chronocoulometric data that is comparable with the value obtained by potentiometry.     

Band-type microelectrodes for amperometric immunoassays

A band-type microelectrode was made using a parylene-N film as a passivation layer. A circular-type, mm-scale electrode with the same diameter as the band-type microelectrode was also made with an electrode area that was 5000 times larger than the band-type microelectrode. By comparing the amperometric signals of 3,5,3′,5′-tetramethylbenzidine (TMB) samples at different optical density (OD) values, the band-type microelectrode was determined to be 9 times more sensitive than the circular-type electrode. The properties of the circular-type and the band-type electrodes (e.g., the shape of their cyclic voltammograms, the type of diffusion layer used, and the diffusion layer thickness per unit electrode area) were characterized according to their electrode area using the COMSOL Multiphysics software. From these simulations, the band-type electrode was estimated to have the conventional microelectrode properties, even when the electrode area was 100 times larger than a conventional circular-type electrode. These results show that both the geometry and the area of an electrode can influence the properties of the electrode. Finally, amperometric analysis based on a band-type electrode was applied to commercial ELISA kits to analyze human hepatitis B surface antigen (hHBsAg) and human immunodeficiency virus (HIV) antibodies.     

Monitoring metal ion contamination onset in hydrofluoric acid using silicon-diamond and dual silicon sensing electrode assembly.

Potentiometric detection of trace levels of metallic contamination onset in hydrofluoric acid using a silicon-based sensor in conjunction with two non-contaminating reference electrode systems is presented in this paper. In the first case, conductive diamond was used as a non-contaminating reference electrode. Cyclic voltammetry and open-circuit potential experiments demonstrated the feasibility of using a conductive diamond film electrode as a quasi-reference electrode in the HF solution. In the second case, a dual silicon electrode system was used with one of the silicon-based electrodes protected with an anion permeable membrane behaving as the quasi-reference electrode. The dual silicon sensing electrode system possessed an additional operational advantage of being unaffected by the solution acidity. Though both sensing configurations were able to detect the metal ion contamination onsets at the parts-per-trillion to parts-per-billion levels, the dual silicon electrode design showed a greater compatibility for the on-line detection of metallic impurities in HF etching baths commonly used in semiconductor processing.     

Voltammetric determination of trace mercury at a sonogel-carbon electrode modified with poly-3-methylthiophene

The sonogel-carbon electrode is a new class of sol-gel electrode that exhibit favourable mechanics and electrics properties to be used as electrochemical sensor. In this paper, a modified sonogel-carbon electrode is proposed to determine mercury at trace levels. The modified electrode is obtained by electropolymerization of 3-methylthiophene on the surface of a bare sonogel-carbon electrode. This electrode shows high selectivity and sensitivity and linear response towards Hg(II), with a detection limit of 1.4 × 10⁻³ mg l⁻¹. The electrode is reusable by a simple chemical cleaning procedure. No deterioration was observed in the electrode response during at least 1 week of successive measurements.     

Rotating Ring (Pt)–Disc (FeS2) Electrode Behavior in Hydrochloric Solutions

A rotating ring (Pt)–disc (FeS₂) electrode was used to investigate the surface oxidation process of pyrite in the hydrochloric solutions. It is reported for the first time that the oxidation intermediates of pyrite were formed on the disc electrode and then oxidized on the ring electrode. The results indicate that at a rotation rate of 20 Hz, when the disc electrode potential was in the region of 0.43 to 0.62 V and the ring electrode potential was at 1 V vs a standard calomel electrode (SCE), approximately 50% of the reacted pyrite was oxidized to ferric and sulfate ions and the other 50% was oxidized to sulfur and ferrous ions on the disc electrode. The latter was further oxidized to ferric ions on the ring electrode. As the disc electrode potential increased to 1.22 V vs SCE, more than 90% of the reacted pyrite was oxidized to ferric and sulfate ions on the disc electrode and less than 10% formed ferrous ions, which were further oxidized to ferric ions on the ring electrode.     

Implementation of a Chloride‐selective Electrode Into a Closed Bipolar Electrode System with Fluorimetric Readout

Applicability of a bipolar electrode system was tested for arrangements containing a typical ion‐selective electrode (ISE) connected with an electrode coated by a conducting polymer characterized by electroluminescence. In this case a selective response of the ISE membrane at one pole of the bipolar electrode is transduced to a fluorimetric signal obtained by reduction of the conducting polymer at the second pole. This signal transformation mode was studied on example of a simple closed bipolar electrode system composed of all‐solid‐state chloride‐selective electrode with polypyrrole transducer as the sensing pole and the reporting pole represented by electrode coated by poly(3‐octylthiophene) (POT) layer characterized by fluorescence in the neutral state. In this system selective and linear dependences of fluorimetric signal on logarithm of chloride ions concentration in turn‐on mode were recorded for optimized external voltage applied. Alternatively, a concept of cascade bipolar electrode system with incorporation of additional bipolar electrode being a polarization source for the sensing bipolar electrode with ISE and POT layer was also tested. A significant advantage of the cascade system is its possibility to work spontaneously without external polarization. For this case also linear calibration plots of fluorimetric signal vs. logarithm of analyte concentration were recorded.