摘要:

AbstractThe electroanalytical utility of electrodes modified with inorganic films is reviewed. Various types of inorganic layers (metal oxides, polynuclear transition metal cyanides, zeolites, metal porphyrins and phthalocyanines) are assessed. Various detection schemes based on these modified surfaces are described in 129 references.

ISSN:1040-0397    

DOI:10.1002/elan.1140030902

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractThe synthesis and utilization of electrodes modified with conducting polymers is reviewed. Specific issues evaluated include the various approaches available to produce the required functionality at the electrode surface and the practical considerations to be addressed during synthesis, both in terms of hardware requirements and the chemistry of electropolymerization. The review concludes with a survey of the many applications of polymer‐modified electrodes and includes 112 reference

ISSN:1040-0397    

DOI:10.1002/elan.1140030903

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractThe cathodic current for the reduction of benzoquinone at a glassy carbon electrode was increased in the presence of nucleoside oxidase and inosine. This was attributed to the regeneration of benzoquinone from hydroquinone by the laccaselike reaction of the enzyme, the rate of which depended on the concentration of inosine in the solution. Accordingly, an enzyme electrode for nucleosides was constructed by immobilizing nucleoside oxidase behind a dialysis membrane on a carbon paste electrode containingp‐benzoquinone or hydroquinone. The current response of the electrode to nucleosides was studied and the results were discussed on the basis of the laccaselike activity of the enzyme. The nucleoside oxidase‐modified electrode was tested as an amperometric enzyme electrode for nucleosides and could be used at least for three we

ISSN:1040-0397    

DOI:10.1002/elan.1140030904

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractElectrochemical anodic treatment at ultrasmall carbon ring electrodes appears to result in the formation of an oxide film that displays charge‐selective and pH‐dependent enhancements following treatment. Voltammetry after treatment in pH 7.4 citrate‐phosphate buffer is more Nernstian for dopamine (DA) and less Nernstian for 3,4‐dihydroxyphenylacetic acid (DOPAC). However, oxidation in pH 2.8 buffer gives rise to voltammetry that is less Nernstian for both DA and DOPAC. Extensive surface oxidation in potassium hydroxide apparently forms a thick layer that acts like a thin layer reservoir for adsorbed analyte. Voltammetry following extensive treatment is attenuated and peak shaped. Minimal surface oxidation in KOH results in more Nernstian sigmoidal voltammetry with only light current attenuation. The data suggest that an oxide layer formed following anodic treatment is non‐uniform and leaves sites of activated carbon exposed on the surface. Furthermore, it appears that this layer has cation‐exchange properties giving rise to charge transfer selectivity. A model of the surface formed following anodic oxidation is consistent with previous models involving both surface cleanliness and carbon structure

ISSN:1040-0397    

DOI:10.1002/elan.1140030905

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractThe potentiometric anion responses of polymeric membranes doped with various indium (III)‐porphyrin structures are examined. The appropriate membranes are prepared by incorporating 1.0 wt % of the In(III)‐porphyrins in plasticized poly(vinyl chloride) films. When such membranes are incorporated within standard ion selective electrode bodies, the resulting electrodes display non‐Hofmeister anion selectivity, with a particularly enhanced and super‐Nernstian response to chloride. Among those porphyrins investigated, membranes doped with chloro(octaethylporphyrinato)indium(III) yield the largest and most reproducible potentiometric anion responses. These same membrane electrodes exhibit negligible response to protons (or hydroxide) in the range of pH 4.5–9.0. When utilized as a flow‐injection detector in conjunction with a protein diluent/buffer stream, the In(III)‐porphyrin based electrodes may be used to determine chloride levels in human

ISSN:1040-0397    

DOI:10.1002/elan.1140030906

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractThe quasi‐reversible electron transfer of monosubstituted ferrocenes at a gold electrode in acetonitrile, water, and an aqueous surfactant solution is characterized by formal potentials, diffusion coefficients, heterogeneous electron transfer rate constants, and transfer coefficients. These system parameters are calculated from peak potentials, peak currents, and peak potential differences by means of the multiparameter estimation technique. The results are compared with those of a combined evaluation of rotating disk electrode (rde) and cyclic voltammetric data. The former method can be used even if the rde results are distorted by filming of the electrode. The size of the molecules and, in the case of surfactant addition, the size of micelles containing the ferrocenes is estimated from diffusion coefficients. The electrochemical properties are discussed in view of future applications of these compounds as mediators in amperometric biosensor

ISSN:1040-0397    

DOI:10.1002/elan.1140030907

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractAmalgam‐forming metals can be determined by anodic stripping voltammetry in solutions containing dissolved oxygen. The procedure uses a modified mercury film electrode prepared by deposition of mercury on the surface of a silica‐gel/carbon composite electrode. Between determinations the film is removed from the electrode surface either mechanically or by a potential pulse. Lead was determined over the concentration range from 0.01 to 250 μM, with relative standard deviation values not exceeding ± 5%. The method was applied for the determination of metals in used moto

ISSN:1040-0397    

DOI:10.1002/elan.1140030908

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractThe preparation, properties, and response characteristics of polymeric ion‐selective membrane electrodes prepared from poly(vinylbenzyl chloride) functionalized with quaternary ammonium groups are described. Notably, a carbon‐support electrode coated with a film of poly(trihexylvinylbenzylammonium thiocyanate) yielded a highly selective Nernstian response to thiocyanate in the concentration range 5 × 10−5−0.1 M. The selectivity of this membrane electrode can be favorably compared with that of conventional thiocyanate ion‐selective electrodes. The use of functionalized polymer membranes with solid‐support electrodes represents an interesting alternative to conventional polymer

ISSN:1040-0397    

DOI:10.1002/elan.1140030909

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractThe application of quaternary ammonium functionalized polymers to voltammetric analysis is described. A glassy carbon electrode coated with a thin film of poly(trihexylvinylbenzylammonium chloride) exhibited attractive permselectivity to uric acid. Typically, this polymer‐modified electrode yielded a linear voltammetric response to uric acid in the concentration range of 1–10 μM. The ion exchange properties of poly(trihexylvinylbenzylammonium chloride) was related to the Gibbs‐Donnan equation. Also, chronoamperometry was used to probe the charge‐transport and response mechanisms within this type of ionic poly

ISSN:1040-0397    

DOI:10.1002/elan.1140030910

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY

摘要:

AbstractNovel solvent systems have been developed for the casting of size exclusion electrode modifications by the phase‐inversion process. Solvent systems studied were (solvent/nonsolvent): pyridine/2‐octanol, pyridine/cyclohexanol, acetone/2‐octanol, tetrahydrofuran/aqueous Mg(ClO4)2, and tetrahydrofuran/toluene. These were compared to modifications made from the solvent system acetone/aqueous Mg(ClO4)2. The membranes were cast onto Pt microelectrodes embedded in glass. Cyclic voltammograms were recorded once per min after immersing the membrane‐modified electrode into a solution containing an electroactive species. Modified electrode response time to a concentration perturbation is correlated with the percent nonsolvent and percent polymer in the casting solution. The magnitude of the current from a solution of a 1500 dalton polyethylene glycol ferrocene carboxylate ester solute, and good casting reproducibility. This formulation is recommended for permselective coating applications; applications to biosensors are env

ISSN:1040-0397    

DOI:10.1002/elan.1140030911

出版商:VCH Verlagsgesellschaft mbH    

年代:1991

数据来源: WILEY