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.

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.

scholarly journals Determination of the free-ion concentration of rare earth elements by an ion-exchange technique: implementation, evaluation and limits

2016 ◽  
Vol 13 (3) ◽  
pp. 478 ◽  
Author(s):  
Sébastien Leguay ◽  
Peter G. C. Campbell ◽  
Claude Fortin
Keyword(s):  
Ion Exchange ◽  
Natural Organic Matter ◽  
Metal Ion ◽  
Exchange Resin ◽  
Ion Exchange Resin ◽  
Ion Concentration ◽  
Free Ion ◽  
Free Metal ◽  
Free Metal Ion ◽  
Exchange Technique

Environmental context The lanthanides are a group of heavy elements (from lanthanum to lutetium) increasingly used in many electronic consumer products and little is known about their environmental mobility and toxicity. In natural systems, these elements will bind to natural organic matter but metal toxicity is usually defined by the free metal ion concentration. Here, we propose a method based on sample equilibration with an ion-exchange resin to measure the free lanthanide ion concentration in the presence of natural organic matter. Abstract An ion-exchange technique that employs a polystyrene sulphonate ion-exchange resin was developed for determining environmentally relevant free-ion concentrations of Ce, Eu, La and Nd. Owing to the high affinity of rare earth elements (REE) for the selected resin, this method requires the addition of an inert salt to increase the concentration of the counter-ions (i.e. cations that are exchanged with REE bound to the resin). The use of a batch equilibration approach to calibrate the resin allowed the implementation of the ion-exchange technique at reasonably low ionic strength (I = 0.1M). Several ligands were used to test the selectivity of the method, which proved to be highly selective for the free metal ion in presence of the tested cationic and anionic complexes (REE–nitrate, REE–malic acid and REE–nitrilotriacetic acid systems) and operational for very low proportions of REE3+, owing to the strong REE–resin interactions. The ion-exchange technique was also implemented to determine [Eu]inorg in the presence of natural humic matter (Suwannee River Humic Acid) and the results were compared with those obtained using equilibrium dialysis and those calculated with chemical equilibrium models. At pH 4.00, the measured [Eu]inorg values were in fairly good agreement with those predicted with the Windermere Humic Aqueous Model and Stockholm Humic Model, whereas the Non-Ideal Competitive Absorption model appeared to underestimate the [Eu]inorg. However, the inorganic europium concentrations were strongly underestimated (4 < [Eu]inorg, IET/[Eu]inorg, calc < 18) with the three prediction models at higher pH (5.3 and 6.2).

scholarly journals Metal speciation and bioavailability: revisiting the 'big questions'

2009 ◽  
Vol 6 (4) ◽  
pp. 290 ◽  
Author(s):  
Janet G. Hering
Keyword(s):  
Metal Ion ◽  
Environmental Chemistry ◽  
Metal Speciation ◽  
Environmental Context ◽  
Metal Stress ◽  
Metal Species ◽  
Sufficient Information ◽  
Analytical Approaches ◽  
Free Metal ◽  
Free Metal Ion

Environmental context. Four decades of research on metal speciation and bioavailability have failed to answer the ‘big questions’ of the ecological consequences of metal stress. Important, though still insufficient, insights have been gained from analytical approaches derived from inorganic environmental chemistry (targeting the quantification of free metal ion or ‘labile’ metal concentrations) and from organic environmental chemistry (focusing on the structure of ambient metal species). The ‘omics’ approach, not yet widely applied to this topic, offers the possibility of providing sufficient information to identify a quantitative signature of metal stress.

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