摘要:

AbstractThe properties and applications of amperometric gas sensors are reviewed. An introductory discussion of the general mechanism of electrochemical gas reactions and an outline of the construction of amperometric gas sensors is presented. The performance of sensors and the relationship of the sensor's performance to the materials of construction and sensor components are described. The analytical characteristics of a sensor such as sensitivity, selectivity, response time and noise are intimately related to the materials chosen for membranes, conductive electrolytes, and active electrocatalysts, as well as the choice of effective operating conditions. The applications of amperometric gas sensors to specific analytical problems are discussed in the context of required performance. Finally, this article points out technical gaps and the future direction of amperometric gas sensor research including some potential applications. References that are relevant to the field of amperometric gas sensors are summarized in a table which contains the author's name, the electrochemical reaction, and an exemplary application.

ISSN:1040-0397    

DOI:10.1002/elan.1140040302

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractMedium exchange between electrolysis and stripping steps affords numerous advantages in both voltammetric and potentiometric stripping techniques. A new electrode design for batch mode stripping analysis that allows simple medium exchange under potentiostatic control is described. This is achieved by adherence of a drop of sample to a glass tube containing a glassy‐carbon disc working electrode and a porous ceramic plug, which is in liquid contact with the inner solution in which the reference and counter electrodes are situated. The electrode can be used both for manual operation and for an automated system with a sample changer. Its use is demonstrated in the constant‐current stripping potentiometry determination of the dimethylglyoxime complexes of nickel(II) and cobalt(II) after medium exchange with stripping in 5 M CaCl2, thus avoiding interferences from dissolved oxygen and excessive amounts of zinc(

ISSN:1040-0397    

DOI:10.1002/elan.1140040303

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractA novel glucose biosensor has been prepared by deposition of a mixture containing glucose oxidase dissolved in water and Nafion dissolved in methanol at the surface of a platinum disk electrode. Glucose concentration is evaiuated by measuring the amperometric current corresponding to hydrogen peroxide electrooxidation at 0.7 V vs. SCE. The addition of glucose oxidase to Nafion resulted in a Nafion‐glucose oxidase film that was more permeable to anionic species than Nafion alone. The calibration curve for glucose is linear from 5 μM up to about 10 mM. In oxygen‐saturated solution, the linear range extended to 15 mM. The optimum pH for the assay was found to be 5.5. The enzyme is not stabilized against temperature deactivation when it is immobilized in Nafion. The Pt/Nafion‐glucose oxidase electrodes showed good stability when stored dry at room temperature with 80% of the initial response retained after 25

ISSN:1040-0397    

DOI:10.1002/elan.1140040304

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractAn electrochemical assay for tissue plasminogen activator (t‐PA) is described. The activity of t‐PA is measured in a coupled assay following the amidolytic cleavage of a synthetic tripeptide by the enzyme plasmin. The released electroactive label, p‐aminophenol, is detected anodically either at a glassy carbon indicator electrode or at a platinized activated carbon electrode in a specially constructed perspex cell. Calibration plot data for t‐PA are presented for buffered samples using the perspex block‐type cell. The limit of detection for t‐PA in this assay is 0.25 IU/ml. In addition, the assay format is adapted to yield kinetic information using repetitive square wave voltammetry as the mode o

ISSN:1040-0397    

DOI:10.1002/elan.1140040305

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe electrochemical behavior and the analytical utility of hydrous oxide films, formed on iridium by voltammetric cycling, have been studied by evaluating the dependence of the apparent Standard Electrode Potential (E°′) and the ratio of protons to electrons (p/e) participating in the potential determining equilibria on the charge storage capacity. A model based on electron exchange involving protons in solution and conductive sites on the hydrous oxide surface is proposed and it is shown that an increase in population of the conductive sites can be correlated with an enhancement in proton exchange capacity. The influence of the pretreatment is shown to be an important factor in determining bothE°′ and p/e. The implications of these results for the use of hydrous iridium oxide electrodes as potentiometric pH sensors are consi

ISSN:1040-0397    

DOI:10.1002/elan.1140040306

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe systematic characterization and optimization of bovine erythrocyte glutathione peroxidase is described, together with its application in an assay employing amperometry in stirred solutions for the determination of endogenous levels of reduced glutathione (GSH). Initial studies employed UV spectroscopy, cyclic voltammetry, and amperometry in stirred solutions (to construct hydrodynamic voltammograms) for several investigations including the selection of a suitable hydroperoxide second substrate, the investigation of solution conditions on the enzyme reaction rate, and reconstituted enzyme stability. Subsequently, amperometry in stirred solutions was used to monitor the enzyme‐catalyzed rate of GSH oxidation and to construct calibration plots over the concentration range 10 to 50 μM (corresponding to normal circulating GSH levels after the envisaged sample preparation step consisting of a simple twenty fold dilution of whole blood). Enzyme selectivity studies were performed using several potential physiological interferents and selected pharmaceuticals that may be encountered in the circulation of patients being treated for rheumatoid arthritis. The coefficient of variation for the enzyme linked amperometric assay was 7.28% (n= 5) for solutions containing 40 μM

ISSN:1040-0397    

DOI:10.1002/elan.1140040307

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractA computational strategy is presented for the simulation of current‐voltage curves of electrode processes with very fast coupled homogeneous kinetics at the channel electrode. The approach is illustrated by consideration of the EC′ mechanism that relates to the homogeneous catalysis of electrochemical reactions. It is shown that for fast catalytic reactions “split” voltammetric waves are observed where the two components of the wave result first from the direct reduction (oxidation) of a mediator and, secondly, to a prewave in which mediated reduction of a substrate take

ISSN:1040-0397    

DOI:10.1002/elan.1140040308

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractRegeneration of the initial concentrations at a solid, stationary disk electrode after each reverse pulse in the reverse pulse voltammetry simplifies interpretation of the experimental data but requires modification of the waveform. The modification examined in this work involved inserting a waiting period after each reverse pulse at the potential where the initial concentrations could be reproduced. For conventional disk sizes and a wide range of τ, which is the sum of generating time and pulse time, the minimum length of the waiting time was found theoretically to be 12

ISSN:1040-0397    

DOI:10.1002/elan.1140040309

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractA method for the on‐line removal of dissolved oxygen has been developed and applied to the determination of metals by anodic stripping voltammetry in flowing solutions. The removal of oxygen results from a photochemical reaction between the supporting electrolyte and oxygen, induced by ultraviolet light directed into the detector flow cell. Organic acids such as citric, formic, and oxalic acids have been used as supporting electrolytes. Citric acid was found to be the most efficient oxygen scavenger. The removal of oxygen with this acid was also more efficient than conventional removal with nitrogen gas. The determination of Cu, Cd, and Pb was used to demonstrate the metho

ISSN:1040-0397    

DOI:10.1002/elan.1140040310

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractA model of cathodic stripping square‐wave voltammetry (SWV) of insoluble mercuric salt accumulated at the mercury drop electrode surface is developed. Theoretical relationships between the properties of responses and the parameters of both the redox reaction and the SWV signal are analyzed. Both reversible and quasireversible redox reactions are considered. The nature of quasireversible maximum is discussed. Numerical simulations are compared qualitatively with the SW stripping voltammograms of electrodeposited Hg

ISSN:1040-0397    

DOI:10.1002/elan.1140040311

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY