AGNES at vibrated gold microwire electrode for the direct quantification of free copper concentrations.
The free metal ion concentration and the dynamic features of the metal species are recognized as key to predict metal bioavailability and toxicity to aquatic organisms. Quantification of the former is, however, still challenging. In this paper, it is shown for the first time that the concentration of free copper (Cu(2+)) can be quantified by applying AGNES (Absence of Gradients and Nernstian equilibrium stripping) at a solid gold electrode. It was found that: i) the amount of deposited Cu follows a Nernstian relationship with the applied deposition potential, and ii) the stripping signal is linearly related with the free metal ion concentration. The performance of AGNES at the vibrating gold microwire electrode (VGME) was assessed for two labile systems: Cu-malonic acid and Cu-iminodiacetic acid at ionic strength 0.01 M and a range of pH values from 4.0 to 6.0. The free Cu concentrations and conditional stability constants obtained by AGNES were in good agreement with stripping scanned voltammetry and thermodynamic theoretical predictions obtained by Visual MinteQ. This work highlights the suitability of gold electrodes for the quantification of free metal ion concentrations by AGNES. It also strongly suggests that other solid electrodes may be well appropriate for such task. This new application of AGNES is a first step towards a range of applications for a number of metals in speciation, toxicological and environmental studies for the direct determination of the key parameter that is the free metal ion concentration.
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Torre Sul Lab 11-6.3, Av. Rovisco Pais #1, 1049-001 Lisbon, Portugal. Electronic address: rdomingos@ipgp.fr.
Rute F
RF
Domingos
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Torre Sul Lab 11-6.3, Av. Rovisco Pais #1, 1049-001 Lisbon, Portugal.
Sara
S
Carreira
Department of Chemistry, University of Lleida and Agrotecnio, Rovira Roure 191, 25198 Lleida, Spain.
Josep
J
Galceran
School of Environmental Sciences, University of Liverpool, 4 Brownlow Street, Liverpool L693 GP, United Kingdom.
Pascal
P
Salaün
LIEC/ENSG, UMR 7360 CNRS - Université de Lorraine, 15 Avenue du Charmois, 54500 Vandoeuvre-les-Nancy, France.
José P
JP
Pinheiro
D003300:Copper / Q000032:analysis*; D055664:Electrochemical Techniques / Q000295:instrumentation*; D004566:Electrodes; D004595:Electroplating; D006046:Gold / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D057230:Limit of Detection; D009994:Osmolar Concentration; D014867:Water / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*
D014874:Water Pollutants, Chemical; D014867:Water; D006046:Gold; D003300:Copper
AGNES; Copper; Gold electrode; Speciation; Stripping scanned voltammetry; VGME