Dynamic Speciation Analysis of Heterogeneous Metal Complexes with Natural Ligands by Stripping Chronopotentiometry at Scanned Deposition Potential (SSCP)

2004 ◽  
Vol 57 (10) ◽  
pp. 983 ◽  
Author(s):  
Raewyn M. Town ◽  
Herman P. van Leeuwen
Keyword(s):  
Metal Complexes ◽  
Humic Substances ◽  
Metal Binding ◽  
Metal Speciation ◽  
Speciation Analysis ◽  
Deposition Potential ◽  
Stripping Chronopotentiometry ◽  
Determination Of Parameters ◽  
Apparent Stability

Stripping chronopotentiometry at scanned deposition potential (SSCP) allows chemical heterogeneity in metal speciation to be unambiguously identified. In the labile regime, use of the Freundlich binding isotherm allows straightforward determination of parameters to describe the apparent stability and heterogeneity of metal complexes with humic substances. The extent of heterogeneity of metal binding by several humic substances follows the order Cu(ii) >> Pb(ii) > Cd(ii). The lability of metal complexes decreases from the foot to the top of the wave, and the greater the degree of heterogeneity, the more readily lability is lost. In the kinetic current regime, the Koutecký–Koryta approximation allows an expression to be obtained for the SSCP wave that provides a good estimate of the experimental data for metal complexes with moderate degrees of heterogeneity.

Scanned stripping chronopotentiometry at bismuth film rotating disc electrodes: a method for quantitative dynamic metal speciation

2014 ◽  
Vol 11 (2) ◽  
pp. 150 ◽  
Author(s):  
Jose Paulo Pinheiro ◽  
Luciana S. Rocha ◽  
Danielle Goveia ◽  
Raewyn M. Town
Keyword(s):  
Metal Speciation ◽  
Speciation Analysis ◽  
Deposition Potential ◽  
Bismuth Film ◽  
Rotating Disc ◽  
Stripping Chronopotentiometry ◽  
Mercury Electrodes ◽  
Disc Electrodes ◽  
Bismuth Electrodes

Environmental context Electroanalytical methods have found wide application in trace metal speciation analysis in environmental systems. The need to find functional alternatives to mercury electrodes for in situ speciation studies has encouraged the use of bismuth as a solid-state electrode substrate. We demonstrate the utility of bismuth electrodes for quantitative dynamic speciation analysis. Abstract Bismuth film electrodes are employed for dynamic metal speciation analysis of PbII complexes by stripping chronopotentiometry at scanned deposition potential (SSCP). Their performance is found to be comparable to that of mercury-film electrodes. The quantitative SSCP expressions that describe the thermodynamic and kinetic complexation parameters are straightforwardly applicable to this solid electrode.

Lead electrochemical speciation analysis in seawater media by using AGNES and SSCP techniques

2014 ◽  
Vol 11 (2) ◽  
pp. 137 ◽  
Author(s):  
Margarita Díaz-de-Alba ◽  
M. Dolores Galindo-Riaño ◽  
José Paulo Pinheiro
Keyword(s):  
Natural Organic Matter ◽  
Metal Ion ◽  
Metal Speciation ◽  
Speciation Analysis ◽  
Deposition Potential ◽  
Visual Minteq ◽  
Ph Values ◽  
Stripping Chronopotentiometry ◽  
Theoretical Predictions ◽  
Free Metal

Environmental context Metal contamination of seawater can present severe environmental problems owing to the high toxicity of metals and their persistence in the environment. This study explores the possibility of analysing lead in seawater media using two recently developed electrochemical methods. The methods are shown to be very useful tools to monitor the behaviour and fate of lead and other metals in seawater. Abstract The speciation of PbII in synthetic and real seawater is studied by absence of gradients and Nernstian equilibrium stripping (AGNES) and stripping chronopotentiometry at scanned deposition potential (SSCP). The usefulness of the combination of both techniques in the same electrochemical cell for trace metal speciation analysis is assessed at different pH values (2.7, 5.0, 6.0, 7.0 and 8.6). The AGNES (free metal ion concentrations) and SSCP (stability constants) results for synthetic seawater agree reasonably with each other and with the theoretical predictions of the software Visual MINTEQ 3.0. This is also true for real seawater media below pH 7.0. Because of the influence of natural organic matter (2.01mgL–1 total organic carbon) in the real seawater at pH 7.0 and 8.6 the SSCP signal showed that the PbII complexes became less labile and were formed by chemically heterogeneous ligands. At these pH values, free metal concentrations determined by AGNES agreed with concentrations predicted by Visual MINTEQ using a generic fulvic acid concentration.

Determination of diffusion coefficients of nanoparticles and humic substances using scanning stripping chronopotentiometry (SSCP)

2007 ◽  
Vol 295 (1-3) ◽  
pp. 200-208 ◽  
Author(s):  
José P. Pinheiro ◽  
Rute Domingos ◽  
Rocio Lopez ◽  
Roberta Brayner ◽  
Fernand Fiévet ◽  
...  
Keyword(s):  
Humic Substances ◽  
Diffusion Coefficients ◽  
Stripping Chronopotentiometry

Gel–water partitioning of soil humics in diffusive gradient in thin film (DGT) analysis of their metal complexes

2012 ◽  
Vol 9 (1) ◽  
pp. 24 ◽  
Author(s):  
Pascal L. R. van der Veeken ◽  
Herman P. van Leeuwen
Keyword(s):  
Thin Film ◽  
Metal Complexes ◽  
Metal Speciation ◽  
Speciation Analysis ◽  
Fulvic Acids ◽  
Metal Species ◽  
Environmental Media ◽  
Gel Layer ◽  
Basic Features ◽  
Flux Response

Environmental contextMetal species can have significant toxic effects in aquatic systems, and therefore their occurrence should be reliably monitored. Although many methods to measure metal species are available, they all have limitations and are sensitive to physicochemical complications. It is shown that, in techniques based on diffusive gradients in thin films, sorption of humic acids affects metal speciation inside the diffusive gel layer and the nature of the ensuing flux response. AbstractMetal complexes of humic and fulvic acids are ubiquitous in aqueous environmental media. In metal speciation analysis by DGT (diffusive gradient in thin film) with polyacrylamide hydrogels, soil humic acid species have been shown to significantly accumulate in the diffusive gel layer. As a result, the speciation of their metal complexes inside the gel is changed with respect to that in the sample medium. In low ionic strength samples, the effects of sorption of the charged humic species are compounded by Donnan partitioning. Here we lay out the basic features that govern the partition of humic species between gel and water, and discuss their effect on the properties of the DGT metal flux.

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