摘要:

AbstractA review of the development and application of extended X‐ray absorption fine structure (EXAFS) spectroscopy for in situ structural characterization of chemical processes at he electrode surface is presented. The designs of the in situ electrochemical cells developed to date are shown. Applications are presented from the areas of metal passivation, spectroelectrochemistry, modified electrodes, underpotential deposition, and adsorptio

ISSN:1040-0397    

DOI:10.1002/elan.1140030303

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractThere is considerable interest in determining trace amounts of cobalt in highly concentrated zinc solutions. Existing commonly used voltammetric methods such as those based on formation of dimethlyglyoxime complexes and adsorptive stripping voltammetry, while very sensitive for the determination of cobalt, do not always provide the necessary discrimination against the zinc (and nickel) processes. In the present work a recently described method, based on the formation and adsorption of a cobalt–α‐benzil dioxime complex and catalyzed by nitrite, has been optimized so at a 106to 107M concentration excess of zinc can be tolerated. Since the method is also relatively insensitive to nickel, it can be applied to highly purified zinc electrol

ISSN:1040-0397    

DOI:10.1002/elan.1140030304

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractHighly sensitive (10−8mol/dm3) and selective voltammetric detection of dopamine can be carried out with a closely spaced planar interdigitated array (IDA) or vertically separated new IDA electrodes. The sensitivity of dopamine was improved up to 10−8mol/dm3as a result of high collection efficiency and redox cycling, because twin electrodes with a very small gap make it possible to collect most of the active species oxidized at adjacent electrodes and then to return them to dopamine by reverse reduction before the chemical reaction has terminated. The influence ofL‐ascorbic acid, which interferes with the detection of catecholamines, may be removed by oxidizing it at one electrode, because the oxidized acid converts rapidly to an electrochemically inactive species and is not detected at the other electrode. Dopamine was detected quantitatively in the presence of 10‐fold excess ofL‐ascorbic acid in the same

ISSN:1040-0397    

DOI:10.1002/elan.1140030305

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractA sensitive two‐site, enzyme‐linked immunoassay utilizing electrochemical detection has been developed forClostridium perfringensphospholipase C (α toxin). Alkaline phosphatase conjugated to a mouse monoclonal antibody is used as the enzyme label. The enzyme activity is measured using 1‐naphthyl phosphate as the enzyme substrate. The enzyme‐generated naphthol is detected amperometrically in a thin‐layer cell at a glassy carbon electrode after chromatography on a 50 mm C8 reverse phase column. Two assay formats are described, based on either microtiter plates or polydispersed polymeric microbeads. The limits of detection of the two assay formats were 67.1 and 13.0 ng/mL, respectively, with a total assay time of less than one hour. The performance characteristics of three possible substrates for the alkaline phosphatase catalyzed reaction are also

ISSN:1040-0397    

DOI:10.1002/elan.1140030306

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractThe potentiometric response of several polymer membrane based ion‐selective electrodes prepared with hydrophobic vitamin B12derivatives is described. The effect of different proteins on the properties of these electrodes is discussed. It is suggested that the observed changes in potential upon addition of proteins are due mainly to nonspecific interactions between the proteins and the polymer membrane. Reduction of the nonspecific binding effect is possible by using a polymer matrix that contains free hydroxyl groups. The observed results agree with a theoretical model, which predicts that the nonspecific binding effect is more evident when membranes loaded with relatively small amounts of ionophore are used. The implications of these observations for the development of biosensors are discusse

ISSN:1040-0397    

DOI:10.1002/elan.1140030307

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractThe electron transfer between excited‐state 9,10‐anthracenedione (325 nm) and sodium tetraphenylborate (tetraphenylboron sodium) in acetonitrile solution is shown to form the radical anion of 9,10‐anthracenedione together with the BPh 4˙radical. The latter is known to decompose to biphenyl and other Products. A new channel electrode methodology is developed and characterized to deduce the mechanism of the reaction and to quantify its

ISSN:1040-0397    

DOI:10.1002/elan.1140030308

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractThe determination of gold by the application of electrodes modified with anion exchangers is considered. Particular attention is paid to investigating the capability of these electrodes to determine gold(III) in the presence of copper(II). Electrodes modified with a film of poly(4‐vinyl‐pyridine) or either chemisorbed electrochemically generated were investigated. It was found that copper(II) caused little or no interference in chloride media. However, copper(II) cyanide complexes interfered with the determination of gold cyanide soluti

ISSN:1040-0397    

DOI:10.1002/elan.1140030309

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractX‐Ray photoelectron spectroscopic (XPS) data of AgCl‐coated, ion‐selective electrodes exposed to solutions containing high concentrations of bromide and iodide ions revealed that the surface properties of the original electrode changed. The mixed phases, AgBrsCl1–sand AgIsCl1–s, seem to form initially on the electrode surface, with the existence of the AgICl phase much shorter than that of the AgBrCl phase. This indicates that the formation of the Agl surface layer is kinetically faster than the formation of the AgBr layer. In both cases XPS data showed the ultimate formation of AgBr and AgI layers on top of the original AgCl‐coated, ion‐selective electrode surface after being subjected to solutions containing either bromide or iodide ions. The conversion of the crystalline‐coated, chloride‐selective electrode surfaces to AgBr and AgI layers, however, transformed the chloride‐selective electrodes into bromide‐ or iodide‐selective electrodes with electrode properties different from those of

ISSN:1040-0397    

DOI:10.1002/elan.1140030310

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractElectrodeposition of the phenothiazine mediator titrant toluidine blue onto a glassy carbon substrate at an appropriate potential was used to construct a toluidine blue chemically modified electrode (CME) exhibiting electrocatalytic reduction for myoglobin and hemoglobin. The CME catalyzed the hemoprotein electroreduction at the reduction potential of the mediator molecule. When the CME as used as a detector for flow injection analysis at a constant applied potential of −0.30 V vs. a saturated calomel electrode, it gave detection limits of 20 and 50 ng (1.2 and 0.78 pmol) injected myoglobin and hemoglobin, respectively, with a dynamic linear concentration range over 2 orders of magnitude. After a brief equilibration period, the CME retained nearly 90% of its initial myoglobin response over 8 hours of continuous exposure to the flow‐through sys

ISSN:1040-0397    

DOI:10.1002/elan.1140030311

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractElectrocatalytic oxidation of ascorbic acid (AA) in aqueous buffer solution at thep‐tetracyanoquinodimethane (TCNQ)‐, ferrocene (Fc)‐, 1,1′‐dimethylferrocene (DMFc)‐, and tetrathiafulvalene (TTF)‐modified graphite electrodes is carried out at each modifier's redox potentials. Over the linear range of current dependence on AA concentration, the sensitivity of the electrocatalytic systems corresponds to up to 0.1 A/M. At pH 6.5–8.0 a change in the electrocatalytic process rate is less evident (for TCNQ, TTF) or is increased by a factor of 4.9 (DMFc). The electrocatalytic current is only slightly dependent on electrode rotation speed. The electrodes retain about 80% of their initial response over a 2‐month pe

ISSN:1040-0397    

DOI:10.1002/elan.1140030312

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY