摘要:

AbstractAn improved mathematical model of dynamic responses of a glass pH electrode and its correlation with that of a membrane‐mounted glass pH electrode on the basis of HCl diffusion through the stagnant layer is reported here. The application of such a model and its validity to aqueous and gel films, such as porcine gastric mucus, is evaluated across the pH spectrum. Dynamic responses of the membrane‐mounted glass pH electrode, modelled on this basis gave an excellent fit to the experimental data across the pH range for both films. The modified model described here takes into account the presence of any effect at the membrane/mucus interface for the experimental set‐up. The technique and model thus enables determination of ion flux in mucus or any coated ion selective elec

ISSN:1040-0397    

DOI:10.1002/elan.1140040702

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe binding of Hg(II) with humic acid, incorporated into the carbon paste electrode, was verified. This modified humic acid electrode was used for the trace determination of Hg(II). The differential‐pulse voltammetry on the electrode modified with humic acid yielded good performance over the concentration range 5 × 10−8–5 × 10−7M Hg(II). Only Cu(II) interferes with the dete

ISSN:1040-0397    

DOI:10.1002/elan.1140040703

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe anodic stripping voltammetry of selenium (IV) in a gold fiber electrochemical flow cell is described. The cell is simple to construct and flexible in its operation. The nonlinear diffusional mass transport characteristics of such small diameter electrodes influence the anodic stripping voltammetry of Se(IV) with the result that significant deposition of metal ions occurs during the scan period from the deposition potential to the peak potential. Therefore, an extremely short deposition period of the order of 20 seconds can be employed at the gold fiber electrode. The system described resulted in a linear working range from 0–15 ng/mL, a detection limit of 0.5 ng/mL Se(IV) and a relative standard deviation of 6% at 5 ng/mL (n = 7) in pure solutio

ISSN:1040-0397    

DOI:10.1002/elan.1140040704

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractA computational approach to the calculation of irreversible and quasi‐reversible current voltage curves at channel electrodes is presented. The method has generality since, in particular, no assumptions are made as to the electrode geometry or electrolyte flow rates so that both Lévěque and, with novelty, thin‐layer conditions may be explored. An approximate analytical theory for the shape of current‐voltage curves which predicts the flow rate dependence of the half‐wave potential is presented for the latter case and found to be in good agreement with rigorous computation

ISSN:1040-0397    

DOI:10.1002/elan.1140040705

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractCadmium complexation in chloride‐bromide and chloride‐iodide mixtures of a high ionic strength (I = 4 mol/L) was studied by polarographic/voltammetric methods. In the first case, statistically expected formation constants of mixed‐ligand complexes were confirmed. The presence of iodide ions, however, makes interpretation of the experimental data more difficult because the electrode process becomes complex. In addition to CdI2, which is a well‐known surface‐active species, CdClaI2a−seems to be adsorbed at the merc

ISSN:1040-0397    

DOI:10.1002/elan.1140040706

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractIn acidic chloride media (pH 2), a chelate of Mo(VI) with 1, 10‐phenanthroline is adsorbed on a hanging mercury drop electrode and reduced at −0.575 V. In presence of fulvic acids, the signal is strongly enhanced owing to the formation of a mixed complex which is more readily adsorbed. The effect of various operational parameters (pH, ligand, and molybdenum concentrations, potential and time collection) on the response is discussed, and a sensitive adsorptive voltammetric procedure is develo

ISSN:1040-0397    

DOI:10.1002/elan.1140040707

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe polarograms of mixtures of the cocoa flavor compounds, pyrazines, consist of overlapping peaks. This generally precludes the direct analysis of these compunds without prior separation. In this paper, polarographic conditions for the analysis of up to four component mixtures of pyrazines present at trace levels (150 ppb‐1 ppm) were investigated using differential pulse polarography (DPP) at a static mercury drop electrode (SMDE). A series of pyrazine mixtures were analyzed at pH 4.8 (phosphate/citric acid buffer) and the results were interpreted using partial least squares (PLS), principal component regression (PCR), and multiple linear regression (MLR) chemometric routines. In each case an orthogonally designed training set was used to facilitate predictions. The PLS and the PCR models produced acceptable results with recoveries, in general, being in the 97–104% range and RSD in the 4–10% range depending on the nature and complexity of the mixture ana

ISSN:1040-0397    

DOI:10.1002/elan.1140040708

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe anodic oxidation kinetics of hydrazine (N2H4) on glassy carbon (GC) electrode was examined by cyclic voltammetry, rotating disk and ring‐disc electrode techniques. The possible mechanisms of N2H4oxidation in both aqueous and nonaqueous solutions are propose

ISSN:1040-0397    

DOI:10.1002/elan.1140040709

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe electrochemical reduction behavior of nicoumalone has been studied by using dc polarography, cyclic voltammetry, ac polarography, differential pulse polarography, millicoulometry, and controlled potential electrolysis in universal buffers ranging from pH 2.0 to 12.0 in DMF—water mixtures. Kinetic parameters such as diffusion coefficient (D) and forward rate constant (k f, ho) values are evaluated and a reduction mechanism is proposed. A simple and rapid differential pulse polarographic method has been developed for the determination of nicoumalone in pharmaceutical formulations using the standard addition method. The detection limit is 2.7 ng m

ISSN:1040-0397    

DOI:10.1002/elan.1140040710

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe electroanalytical study of the behavior of 7‐(1′‐vinyl‐3′,3′,5′,5′‐tetramethylhexyl)‐8‐quinolinol, the active component of the commercial extractant Kelex 100 (Ashland Chemicals), at a glassy carbon electrode has been carried out using different voltammetric techniques. The compound is oxidized giving rise to a voltammetric peak in the pH range 1.03–7.27. The plot of the variationEpversus pH shows two straight lines intercepting at 3.46, which corresponds to thepKaivalue of the component. The oxidation process of the compound is irreversible (ān = 1.32) and predominantly diffusion controlled, although with an important adsorptive component. The electrode process can be attributed to the oxidation of the hydroxyl group of the quinolinic ring. A voltammetric method for the determination of the extra

ISSN:1040-0397    

DOI:10.1002/elan.1140040711

出版商:VCH Verlagsgesellschaft mbH    

年代:1992

数据来源: WILEY