Influence of the type of titration and of data treatment methods on metal complexing parameters determination of single and multi-ligand systems measured by stripping voltammetry

Garnier, Cédric; Pižeta, Ivanka; Mounier, Stéphane; Bénaïm, J.; Branica, Marko

doi:10.1016/j.aca.2003.10.066

Cited by 50 publications

(74 citation statements)

References 34 publications

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“…Working electrode 25-μm gold-disk microelectrode metal is inertly complexed. At the end of the curve, a linear section allows determination of the microelectrode sensitivity [33]. In contrast, if the microelectrode response is linear over the whole concentration range scanned, the analysed metal should only be in the labile forms.…”

Section: Calibrationmentioning

confidence: 99%

See 1 more Smart Citation

Voltammetric procedure for trace metal analysis in polluted natural waters using homemade bare gold-disk microelectrodes

Garnier

Lesven²,

Billon³

et al. 2006

Anal Bioanal Chem

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To cite this version:Cédric Garnier, Lesven Ludovic, Billon Gabriel, Magnier Aurélie, Mikkelsen Øyvind, et al.. Voltammetric procedure for trace metal analysis in polluted natural waters using homemade bare gold-disk microelectrodes. Analytical and Bioanalytical Chemistry, Springer Verlag, 2006, 386 (2) Abstract Voltammetric procedures for trace metals analysis in polluted natural waters using homemade bare golddisk microelectrodes of 25-and 125-μm diameters have been determined. In filtered seawater samples, square wave anodic stripping voltammetry (SWASV) with a frequency of 25 Hz is applied for analysis, whereas in unfiltered contaminated river samples, differential pulse anodic stripping voltammetry (DPASV) gave more reliable results. . These microelectrodes have been validated for natural sample analysis by use in an on-site system to monitor Cu, Pb and Zn labile concentrations in the Deûle River (France), polluted by industrial activities. First results obtained on sediment core issued from the same location have shown the ability of this type of microelectrode for in situ measurements of Pb and Mn concentrations in anoxic sediments.

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Section: Calibrationmentioning

confidence: 99%

“…To calibrate the microelectrode over a wide concentration range, additions of the 6 metals were carried out from 0.2 to 50 μg L −1 (to 100 μg L −1 for Mn) in a decade mode [33]. For each addition, the SWASV measurements were repeated twice.…”

Section: -μM Gold-disk Microelectrodementioning

confidence: 99%

Voltammetric procedure for trace metal analysis in polluted natural waters using homemade bare gold-disk microelectrodes

Garnier

Lesven²,

Billon³

et al. 2006

Anal Bioanal Chem

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“…We found that problematic raw titration data in this study could not be fit with the Scatchard linearization method, possibly due to an inappropriate detection window or interference at the HMDE, so these plots appear particularly valuable in processing speciation data, at least in the case of a single ligand class. Future studies should consider evaluating these data interpretation techniques along with other numerical methods (Hudson et al 2003;Garnier et al 2004;Sander et al 2011) for open ocean samples.…”

Section: Comments and Recommendationsmentioning

confidence: 99%

The organic complexation of iron and copper: an intercomparison of competitive ligand exchange‐adsorptive cathodic stripping voltammetry (CLE‐ACSV) techniques

Buck

Moffett

Barbeau

et al. 2012

Limnology & Ocean Methods

108

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Competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV) is used in chemical oceanography to measure the organic complexation of metal ions in seawater. The bioactive trace metals iron, copper, cobalt, nickel, and zinc are all complexed (up to > 99% of iron and copper) by organic ligands in seawater (van den Berg and Nimmo 1987;Coale and Bruland 1988;Bruland 1989;Gledhill and van den Berg 1994;Rue and Bruland 1995;Wu and Luther 1995;Ellwood and van den Berg 2001), which can control solubility and bioavailability of these elements. Measuring the organic complexation of trace metals is, thus, an exceedingly important component of their biogeochemistry. To date, CLE-ACSV is the only widely accepted technique employed for measuring dissolved metalbinding ligand concentrations ([L i ]) in seawater and the conditional stability constants ( ) for their complexes with the metal of interest (M).To accomplish this, CLE-ACSV employs a well-characterized added ligand (AL) to compete against ambient ligands for M over a complete titration of a buffered seawater sample with additions of inorganic metal (M¢; typically from + 0 to + 10 ¥ [M]). Following equilibrium first with the metal additions (typically several hours) and then with the added ligand (minutes to hours), the resulting M(AL) x complex for each titration point is adsorbed to the surface of a hanging mercury drop electrode (HMDE) at a set voltage potential over a deposition time prede- AbstractCharacterization of the speciation of iron and copper is an important objective of the GEOTRACES Science Plan. To incorporate speciation measurements into such a multinational program, standard practices must be adopted that allow data from multiple labs to be synthesized. Competitive ligand exchange-adsorptive cathodic stripping voltammetry (CLE-ACSV) is the primary technique employed for measuring metal-binding ligands and determining metal speciation in seawater. The determination of concentrations and conditional stability constants of metal-binding ligands is particularly challenging, as results can be influenced both by experimental conditions and interpretation of titration data. Here, we report an investigation between four laboratories to study the speciation of iron and copper using CLE-ACSV. Samples were collected on the GEOTRACES II intercomparison cruise in the North Pacific Ocean in May 2009 at 30° N, 140° W. This intercomparison was carried out shipboard and included an assessment of the viability of sample preservation by freezing. Results showed that consensus values could be obtained between different labs, but that some existing practices were problematic and require further attention in future work. A series of recommendations emerged from this study that will be useful in implementing multi-investigator programs like GEOTRACES.

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“…(1) = 20 µmol L −1 ) was included in the simulation as an "overtitration" mechanism for validating the calibration of the slope (Pižeta et al, 2015). The added iron range was extended to cover the range 0.5-30 nmol L −1 (Garnier et al, 2004). Eleven separate titrations were simulated for initial dissolved iron (DFe) concentrations of between 0.05 nmol L −1 and 1.5 nmol L −1 .…”

Section: Methods and Approachmentioning

confidence: 99%

The Effect of Metal Concentration on the Parameters Derived from Complexometric Titrations of Trace Elements in Seawater—A Model Study

Gledhill

Gerringa

2017

Front. Mar. Sci.

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In this study we examine the impact of dissolved metal concentrations on the parameters that are commonly determined from complexometric titrations in seawater. We use the non-ideal competitive adsorption (NICA) model within the framework of the chemical speciation program visual MINTEQ with iron as a model metal. We demonstrate that dissolved iron concentrations effect the determined parameters for a heterogeneous binding site distribution with a fixed concentration of dissolved organic carbon. The commonly used terms "ligand concentration" and "binding constant" are therefore dependent on metal concentration, so we adopt the terminology suggested by Town and Filella (2000) and use the terms ligand quotient and stability quotient here. The systematic increase in the ligand quotient with dissolved iron concentration likely contributes toward the trend of increasing ligand quotient with dissolved iron concentration observed in field studies, and makes it hard to assign an objective meaning to the parameter. We suggest that calculation of the side reaction coefficient, a parameter that describes the probability that any added metal will be complexed, could be less prone to bias and misinterpretation than calculation of conditional stability and ligand quotients. We explore the impact of experimental design on side reaction coefficients by applying different detection windows, and multiwindow and reverse titration approaches. We identify the method that results in the best estimates of side reaction coefficients over a range of iron concentrations between 0.1 and 1.5 nmol L −1 . We find that single window titrations can only reliably estimate side reaction coefficients over a limited range of iron concentrations. Multiwindow titrations provided estimates of side reaction coefficients within the 99% confidence interval of the values calculated directly from the NICA model at all iron concentrations examined here. We recommend that future reports of speciation measurements consider the potential influence of metal concentrations on the determined parameters and future studies focus on developing and applying experimental designs that improve the robustness and rigor of chemical speciation analysis in the marine environment.

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Influence of the type of titration and of data treatment methods on metal complexing parameters determination of single and multi-ligand systems measured by stripping voltammetry

Cited by 50 publications

References 34 publications

Voltammetric procedure for trace metal analysis in polluted natural waters using homemade bare gold-disk microelectrodes

Voltammetric procedure for trace metal analysis in polluted natural waters using homemade bare gold-disk microelectrodes

The organic complexation of iron and copper: an intercomparison of competitive ligand exchange‐adsorptive cathodic stripping voltammetry (CLE‐ACSV) techniques

The Effect of Metal Concentration on the Parameters Derived from Complexometric Titrations of Trace Elements in Seawater—A Model Study

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