Comparison of AGNES (absence of gradients and Nernstian equilibrium stripping) and SSCP (scanned stripping chronopotentiometry) for trace metal speciation analysis

Domingos, Rute F.; Huidobro, C.; Companys, Encarnació; Galceran, Josep; Puy, Jaume; Pinheiro, José Paulo

doi:10.1016/j.jelechem.2008.02.002

Cited by 38 publications

(35 citation statements)

References 33 publications

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“…The dissolution of the QD was followed by the electroanalytical technique scanned stripping chronopotentiometry (SSCP) (Pinheiro and van Leeuwen 2004). The free Cd in solution was quantified by the absence of gradients and Nernstian equilibrium stripping (AGNES) technique (Domingos et al 2008). Special emphasis was placed on (1) precisely quantifying the free Cd in solution; (2) determining the Cd concentration in solution arising from the dissolution of the CdS shell; (3) determining the role of pH and exposure time (until 48 h); and (4) determining the effect of the presence of small organic ligands, such as histidine, glycine, and citric acid.…”

Section: Responsible Editor: Philippe Garriguesmentioning

confidence: 99%

“…The SSCP (Pinheiro and van Leeuwen 2004;Domingos et al 2007Domingos et al , 2008 and AGNES techniques (Companys et al 2005;Domingos et al 2008) are described in the Supporting information. SSCP and AGNES experiments were performed using an Eco Chemie μAutolab III potentiostat in conjunction with a Metrohm 663VA stand and a personal computer using the GPES 4.9 software (Eco Chemie).…”

Section: Sscp and Agnesmentioning

confidence: 99%

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Stability of core/shell quantum dots—role of pH and small organic ligands

Domingos¹,

Franco²,

Pinheiro

2013

Environ Sci Pollut Res

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The improvement of knowledge about the toxicity and even processability, and stability of quantum dots (QD) requires the understanding of the relationship between the QD binding head group, surface structure, and interligand interaction. The scanned stripping chronopotentiometry and absence of gradients and Nernstian equilibrium stripping techniques were used to determine the concentration of Cd dissolved from a polyacrylate-stabilized CdTe/ CdS QD. The effects of various concentrations of small organic ligands such as citric acid, glycine, and histidine and the roles of pH (4.5-8.5) and exposure time (0-48 h) were evaluated. The highest QD dissolution was obtained at the more acidic pH in absence of the ligands (52 %) a result of the CdS shell solubility. At pH 8.5 the largest PAA ability to complex the dissolved Cd leads to a further QD solubility until the equilibrium is reached (24 % of dissolved Cd vs. 4 % at pH 6.0). The citric acid presence resulted in greater QD dissolution, whereas glycine, an amino acid, acts against QD dissolution. Surprisingly, the presence of histidine, an amino acid with an imidazole functional group, leads to the formation of much strong Cd complexes over time, which may be non-labile, inducing variations in the local environment of the QD surface.

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Section: Responsible Editor: Philippe Garriguesmentioning

confidence: 99%

Section: Sscp and Agnesmentioning

confidence: 99%

Stability of core/shell quantum dots—role of pH and small organic ligands

Domingos¹,

Franco²,

Pinheiro

2013

Environ Sci Pollut Res

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“…This equilibrium can, in the simplest implementation of AGNES, be achieved by applying a potential E 1 , just a few millivolts more negative than the standard formal potential of the couple E8', for a sufficiently long time t 1 . A more elaborate potential program ("2 pulses") has been suggested [14] and applied to different systems such as humic acids [15][16][17] or wine [18]. Regardless of the number of pulses, at the end of the deposition stage, Nernstian equilibrium is reached and there is no gradient in the concentration profiles at each side of the electrode surface.…”

Section: The Charge As Response Function Of Agnesmentioning

confidence: 99%

Determination of Free Metal Ion Concentrations Using Screen‐Printed Electrodes and AGNES with the Charge as Response Function

et al. 2011

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AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) has been implemented with screen-printed electrodes (SPE) for the determination of the free concentration of Zn 2 + , Cd 2 + and Pb 2 + . For SPE, the stripped charge is a suitable response function which does not require the second stage of AGNES to be under diffusion limited conditions. This property can be used in the avoiding of the interference of Pb on [Cd 2 + ] determination. The proportionality factor between stripped charge and concentration of amalgamated metal depends on the volume of mercury and opens the way to a future calibrationless strategy. Zn and Cd complexation with oxalate at various pH-values confirms the suitability of the developed methodology, which compares favourable with the standard one based on the Hanging Mercury Drop Electrode.

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“…Em sistemas heterogêneos, o sinal de SSCP torna-se mais difícil de analisar, tornando-se necessário complementar esta técnica com outras para compreender a especiação, tornando AGNES extremamente interessante, 59 pois permite determinar o íon metálico livre usando o mesmo sistema experimental e com limites de detecção similares.…”

Section: Interpretação Do Sinal De Sscp Para O íOn Metálico Em Presenunclassified

Especiação Dinâmica De Metais Traço Em Ambiente Aquático Usando Cronopotenciometria De Redissolução Anódica

Monteiro¹,

Goveia²,

Rotureau³

et al. 2018

Quim. Nova

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Recebido em 26/01/2018; aceito em 12/04/2018; publicado na web em 22/05/2018 DYNAMIC SPECIATION OF TRACE METALS IN AQUATIC ENVIRONMENT USING ANODIC STRIPPING CHRONOPOTENTIOMETRY. The contamination of natural environments by trace metals has several adverse effects on human health, which is mainly due to the high toxicity, persistence and reactivity of these species in the environment. To understand the bioavailability of trace metals, it is necessary to know the speciation in equilibrium and the dynamic behavior of the system. In this context, the present work aims to present a bibliographic review about the potentialities of the Stripping Chronopotentiometry (SCP) and Stripping Chronopotentiometry at Scanned Deposition Potential (SSCP) in the study of dynamic trace metal speciation. These techniques have low detection limits and do not suffer interference due to the adsorption of organic matter on the surface of the working electrode. Coupling these techniques with the Absence of Gradients and Nernstian Equilibrium Stripping (AGNES) enables simultaneous determination of free ions, complexation equilibrium constants and diffusion coefficients of the complexes, thus providing information on the dynamic and heterogeneity of the metal complexes in the presence of macromolecules or particles. In this paper we will present the theory of dynamic speciation of trace metals, a detailed description of how to use the techniques to obtain this information, and examples of application in model systems and natural samples.Keywords: metal complexes; metal ions; lability; redissolution techniques; deposition time. INTRODUÇÃOO interesse no estudo de metais traço em solução provém da elevada toxicidade, persistência e reatividade de muitos destes no ambiente. Em ambientes aquáticos naturais, os íons metálicos podem se distribuir em diferentes espécies como resultado das interações com componentes da matriz (matéria orgânica, partículas inorgâni-cas) e das características físico-químicas (temperatura, força iônica, pH, potencial redox, presença de outros íons) do meio. A maioria das espécies formadas tem caráter polifuncional e polieletrolítico, apresentando ampla faixa de constantes de velocidade de formação/ dissociação e de tamanhos, que controlam a biodisponibilidade, toxicidade e mobilidade dos íons metálicos. 1O estudo da distribuição dessas espécies é denominado de especiação de metais. O termo especiação foi definido como a descrição da abundância de um elemento numa amostra (distribuição da espé-cie), enquanto a análise de especiação se refere aos procedimentos analíticos de identificação e/ou medida quantitativa de uma ou mais espécies químicas numa amostra. Cada uma destas espécies pode se comportar de forma diferente em termos de mobilidade e biodisponibilidade em sistemas aquáticos naturais, portanto, estão sujeitas à mudança de condições e praticamente nunca atingem o equilíbrio químico. Isto torna o estudo da especiação muito mais complicado, uma vez que se faz necessária uma compreensão da cinética das reações do ...

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Comparison of AGNES (absence of gradients and Nernstian equilibrium stripping) and SSCP (scanned stripping chronopotentiometry) for trace metal speciation analysis

Cited by 38 publications

References 33 publications

Stability of core/shell quantum dots—role of pH and small organic ligands

Stability of core/shell quantum dots—role of pH and small organic ligands

Determination of Free Metal Ion Concentrations Using Screen‐Printed Electrodes and AGNES with the Charge as Response Function

Especiação Dinâmica De Metais Traço Em Ambiente Aquático Usando Cronopotenciometria De Redissolução Anódica

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