Speciation of copper and zinc in natural freshwater: comparison of voltammetric measurements, diffusive gradients in thin films (DGT) and chemical equilibrium models

Meylan, Sébastien; Odžak, Nikša; Behra, Renata; Sigg, Laura

doi:10.1016/j.aca.2003.12.052

Cited by 100 publications

(79 citation statements)

References 29 publications

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“…[26] In aquatic systems, matrix characteristics (e.g. pH, organic matter, presence of other cations) have a strong effect on the chemistry, but this is relatively well integrated into the chemical equilibrium models and we observe acceptable correlations between the measured and the predicted concentrations of the target species, [19,23,27,28] but there are some observed discrepancies noted for soils. [29] Several authors [30][31][32] describe qualitatively the decreasing bioavailability (and toxicity) of a metal with increasing pH or increasing calcium treatment.…”

Section: Introductionmentioning

confidence: 86%

“…The most efficient remains the ion-selective electrode for the determination of free metal activities [12][13][14][15][16][17][18][19] and a variety of voltammetric methods that can measure pools of metals of variable lability. [20][21][22][23][24] All these methods give information on the most available fraction of the trace metals, assumed to be the sum of the free ion, the inorganic complexes and the weak organic complexes. The inert pool can be obtained by difference between total and labile concentrations.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of affinity constants of Cu, Cd, Ca and H for active soil surfaces for a solid phase-controlled soil ligand model

Rachou

Sauvé

2008

Environ. Chem.

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Environmental context. The speciation of metals in soils is controlled by the equilibrium between the solid and aqueous phases and by several parameters such as pH and total metal concentrations. The integration of affinity constants between several cations and active soil surfaces of different soils in the chemical equilibrium modelling software MINEQL+ allows a good evaluation of the chemical speciation of the metals. Abstract.A new approach, derived from the concept of the biotic ligand model, was used for the determination of the affinity constants of Ca, Cu, Cd and H to the active surfaces of different kinds of soils. This approach allowed us to obtain consistent data and to integrate these values in the chemical equilibrium modelling software MINEQL+ and eventually into a solid phase-controlled soil ligand model. This could then very easily be transformed into a terrestrial biotic ligand model by adding constants for biological components. We obtained the chemical speciation of the metals of interest by integrating the initial characteristics of the soil (pH; cation exchange capacity, CEC; total metal concentrations in soil extracts; ionic strength; and CO 2 pressure). Comparison of the predicted and measured values of free Cu 2+ is excellent using soil-specific affinity constants as well as average values. The average affinity constants between the active soil surfaces (S) and the target cations are log K Ca-S = −0.84 (±0.01), log K Cu-S = 5.3 (±0.1), log K Cd-S = 4.4 (±0.2) and log K H-S = 4.1 (±0.2). External soils have been used to validate the conceptual model and the results show a very good correlation between the predicted and the measured free Cu (pCu) except for an acidic soil (pH < 5.2), highlighting the importance of integrating Al into the model.

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Section: Introductionmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Evaluation of affinity constants of Cu, Cd, Ca and H for active soil surfaces for a solid phase-controlled soil ligand model

Rachou

Sauvé

2008

Environ. Chem.

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“…Através de um estudo de comparação de métodos analíticos para análise da especiação de cobre e zinco, Meylan et al 15 compararam a técnica de DGT na determinação de cobre e zinco lábeis com competição por troca de ligantes e voltametria de redissolução anódica para o zinco, e voltametria de redissolução catódica para cobre. A fração total dissolvida de ambos os metais foi determinada através de ICP-MS. Os autores confirmaram que técnicas baseadas em princípios distintos detectam quantidades de metais distintas.…”

Section: Introductionunclassified

“…Tem-se, por exemplo, que a especiação do cobre em águas naturais é frequentemente efetuada através da competição de ligantes com determinação por DPCSV, enquanto que para o zinco normalmente DPASV é usada. 1,[14][15][16][17][18][19] Skoog et al, 20 Harris 21 e Wang 22 relataram que a faixa de trabalho na voltametria é dependente não apenas das características do eletrodo de trabalho, mas igualmente do meio em que ele está imerso. Frequentemente, a faixa de trabalho é limitada por dois processos eletródicos.…”

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Análise de especiação de cobre e zinco empregando voltametria de redissolução anódica com pulso diferencial

Tonietto¹,

Grassi²

2012

Quím. Nova

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Recebido em 10/8/10; aceito em 3/6/11; publicado na web em 22/7/11 SPECIATION ANALYSIS OF COPPER AND ZINC USING DIFFERENTIAL PULSE ANODIC STRIPPING VOLTAMMETRY. This work describes methodologies for speciation analysis of the metals copper and zinc as total, total dissolved, labile, as well as complexation capacity (conditional stability constants and available ligand concentration), using the same technique, differential pulse anodic stripping voltammetry (DPASV). Several supporting electrolytes were tested, and the results showed that KNO 3 and HNO 3 resulted in voltamograms without interferences as well as excellent resolution for the total and labile fractions. The methodology using the DPASV technique allows a simple and low cost analysis of copper and zinc speciation, with high precision and sensitivity, with limits of quantification (LOQ) of 1.8 nmol L -1 for copper and 2.1 nmol L -1 for zinc.Keywords: anodic stripping voltammetry; speciation; trace metal. INTRODUÇÃOEstudos de especiação de metais são de grande importância para a avaliação de impactos ambientais, avaliações ecotoxicológicas, assim como para o entendimento do comportamento e destino dos metais em ambientes aquáticos.1 Informações sobre a reatividade, mobilidade e biodisponibilidade dos metais em águas naturais podem ser obtidas mediante estudos de especiação. A relação entre especiação dos elementos metálicos e toxicidade aos organismos é complexa e depende não somente da espécie química em questão, mas também do organismo exposto e da função fisiológica que o elemento metálico exerce no organismo.2 Sabe-se que os elementos cobre e zinco são essenciais aos organismos aquáticos, mas podem ser tóxicos quando encontrados em concentrações mais elevadas.3 Devido à complexidade da interação metais-organismo-ambiente, o uso de técnicas analíticas capazes de determinar diferentes espécies químicas com baixa manipulação amostral, tal qual a voltametria, assume destaque quanto à compreensão da dinâmica dos metais no ambiente.Sabe-se que o papel biogeoquímico dos metais correlaciona-se com suas formas físico-químicas, as quais incluem espécies associadas ao material particulado, coloidal e dissolvido.3,4 Portanto, avaliar a concentração total de um metal é insuficiente para inferir sobre seu comportamento e destino no ambiente, assim como sobre seus impactos na biota aquática. 1,3,5 Alguns autores consideram que espécies lábeis apresentam maior biodisponibilidade aos organismos aquáticos.6 Por outro lado, metais complexados a ligantes orgânicos são considerados de menor biodisponibilidade. 7A matéria orgânica dissolvida (MOD) exerce um papel fundamental na especiação dos metais-traço; os ligantes orgânicos possuem poder de complexação com metais, 8 cuja força de associação e quantidade de ligantes disponíveis variam com a categoria da MOD.9,10 Os estudos de especiação de metais podem ser realizados empregando-se diferentes abordagens e técnicas analíticas tais como a voltametria de redissolução anódica (DPASV) e voltametria de redissolução catódica (...

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“…Various techniques have been applied to the speciation of copper in environmental matrices, such as surface waters and soil solutions. The most often used are pH potentiometry, [6] cation-exchange resins, [7][8][9] charge separation (Donnan membrane), [10,11] anodic stripping voltammetry, [7,[12][13][14][15][16][17][18][19] diffusive gradients in thin films measurements [18] and cupric ion-selective electrodes (ISE). [3,14,15,[18][19][20][21][22][23][24][25] All these techniques have some advantages and disadvantages and none can be considered universal.…”

Section: Introductionmentioning

confidence: 99%

Use of an ion-selective electrode for free copper measurements in low salinity and low ionic strength matrices

2007

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Environmental context. The toxicity of metals in the environment is controlled by several parameters including total metal concentration, pH and organic and inorganic ligands (type and concentration). The characterisation of different metal pools in natural matrices (e.g. seawater, soil) is important for the evaluation of their toxic impact. The copper ion-selective electrode (Cu-ISE) is a method of choice for the analytical determination of the speciation (i.e. chemical forms) of divalent copper in natural matrices. This paper clarifies several operational parameters in the hope of decreasing variability of results and increasing the application domain of the Cu-ISE.Abstract. The determination of free copper concentrations in natural matrices is critical for the evaluation of copper toxicity. The ISE is one of the few analytical means for determining the direct speciation of free metal species. We have refined the method for low salinity and low ionic strength solutions for application with soil water extracts or fresh waters. Moreover, we have detailed and standardised a method for using a Cu-ISE with an autotitrator. The standardisation shows a good response and allows significant time saving (under 2 h for the calibration). The results obtained using the ISE are compared with those predicted in the presence of different organic ligands or even the lower free Cu 2+ activities resulting from the formation of Cu hydroxyl species. The method was validated for the determination of Cu speciation at environmentally relevant free Cu 2+ activity, i.e. ranging between 10 −14 and 10 −4 M. The chemical equilibrium calculations were made using the MINEQL+ software and the results agree well for pH values between 3 and 10. In terms of precision, the standard deviations of the measured values never exceed 0.1 units, and in terms of accuracy, the measured values were very close to the nominal values, within a range of 0.1. Outside the optimal pH range, the electrode yields higher activity than expected.

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Speciation of copper and zinc in natural freshwater: comparison of voltammetric measurements, diffusive gradients in thin films (DGT) and chemical equilibrium models

Cited by 100 publications

References 29 publications

Evaluation of affinity constants of Cu, Cd, Ca and H for active soil surfaces for a solid phase-controlled soil ligand model

Evaluation of affinity constants of Cu, Cd, Ca and H for active soil surfaces for a solid phase-controlled soil ligand model

Análise de especiação de cobre e zinco empregando voltametria de redissolução anódica com pulso diferencial

Use of an ion-selective electrode for free copper measurements in low salinity and low ionic strength matrices

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