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.

scholarly journals Investigating the Binding Heterogeneity of Trace Metal Cations With SiO2 Nanoparticles Using Full Wave Analysis of Stripping Chronopotentiometry at Scanned Deposition Potential

2020 ◽  
Vol 8 ◽  
Author(s):  
Elise Rotureau ◽  
Luciana S. Rocha ◽  
Danielle Goveia ◽  
Nuno G. Alves ◽  
José Paulo Pinheiro
Keyword(s):  
Trace Metal ◽  
Metal Binding ◽  
Aqueous Dispersion ◽  
Sio2 Nanoparticles ◽  
Deposition Potential ◽  
Cation Binding ◽  
Mathematical Treatment ◽  
Wave Analysis ◽  
Stripping Chronopotentiometry ◽  
Full Wave Analysis

Silica oxides nano- and microparticles, as well as silica-based materials, are very abundant in nature and industrial processes. Trace metal cation binding with these bulk materials is generally not considered significant in speciation studies in environmental systems. Nonetheless, this might change for nanoparticulate systems as observed in a previous study of Pb(II) with a very small SiO2 particle (7.5 nm diameter). Besides, metal binding by those nanoparticles is surprisingly characterized by a heterogeneity that increases with the decrease of metal-to-particle ratio. Therefore, it is interesting to extend this study to investigate different trace metals and the influence of the nanoparticle size on the cation binding heterogeneity. Consequently, the Cd(II), Pb(II), and Zn(II) binding by two different sized SiO2 nanoparticles (Ludox LS30 and TM40) in aqueous dispersion was studied for a range of pH and ionic strength conditions, using the combination of the electroanalytical techniques Scanned Stripping ChronoPotentiometry and Absence of Gradients and Nernstian Equilibrium Stripping. The coupling of these techniques provides the free metal concentration in the bulk (AGNES) and information of the free and complex concentration at the electrode surface for each Stripping Chronopotentiometry at Scanned deposition Potential (SSCP). A recent mathematical treatment allows the reconstruction of a portion of the metal to ligand binding isotherm with the included heterogeneity information using the full SSCP wave analysis. In this work, we observed that the Zn(II) binding is homogeneous, Cd(II) is slightly heterogeneous, and Pb(II) is moderately heterogeneous, whereas the results obtained with the 7.5 nm diameter nanoparticle are slightly more heterogeneous than those obtained with the one of 17 nm. These findings suggest that the Zn(II) binding is electrostatic in nature, and for both Cd(II) and Pb(II), there should be a significant chemical binding contribution.

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