Determination of free metal ion concentrations with AGNES in low ionic strength media
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The determination of free metal ion concentrations of heavy metals, like Zn2+ or Cd2+, with AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) requires an adequate selection of parameters such as deposition potential (linked to the gain, [M-0]/[M2+]) and deposition time. In systems with low ionic strength, the peak potential of the Differential Pulse Polarogram (DPP) measured with low supporting electrolyte is not always suitable for the computation of the gain with existing expressions. The application of AGNES with a constant potential (regardless of the ionic strength) provides a direct measurement of the metal ion activity. When working with low ionic strength solutions, the selection of appropriate instrumentation is important to avoid changes in liquid junction potentials or leakages from the employed electrodes. The deposition times (for a given gain) have not been found to be greatly affected by the probed ionic strengths when working with just metal. A new strategy for the practical implementation of AGNES to measure free metal ion concentrations in samples with low KNO3 or Ca(NO3)(2) concentrations consists in the computation of the deposition potential (to reach a certain gain) from the DPP peak potential at a sufficiently high ionic strength using a new expression. A speciation experiment with Zn2+ and glycine at pHs between 4 and 7.5, where [KNO3] = 0.001 M, shows that this methodology works well and also proves that it is possible to perform AGNES in systems with very low ionic strength. (C) 2012 Elsevier B.V. All rights reserved.
Is part ofJournal of Electroanalytical Chemistry, 2013, vol. 689, num. 15, p. 276-283
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Determination of free metal ion concentrations using screen-printed electrodes and AGNES with the charge as response function Parat, C.; Aguilar Camaño, David; Authier, L.; Potin-Gautier, M.; Companys Ferran, Encarnació; Puy Llorens, Jaume; Galceran i Nogués, Josep (Wiley, 2011)AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) has been implemented with screen-printed electrodes (SPE) for the determination of the free concentration of Zn2+, Cd2+ and Pb2+. For SPE, the stripped charge ...
Direct determination of free metal concentration by implementing stripping chronopotentiometry as second stage of AGNES Parat, C.; Authier, L.; Aguilar, D.; Companys Ferran, Encarnació; Puy Llorens, Jaume; Galceran i Nogués, Josep; Potin-Gautier, M. (The Royal society of Chemistry, 2011)The electroanalytical technique Absence of Gradients and Nernstian Equilibrium Stripping (AGNES) has been extended by applying stripping chronopotentiometry (SCP) as the re-oxidation stage in the determination of the free ...
Free Zn2+ determination in natural freshwater of the Pyrenees: towards on-site measurements with AGNES Parat, C.; Authier, L.; Castetbon,A.; Aguilar Camaño, David; Companys Ferran, Encarnació; Puy Llorens, Jaume; Galceran i Nogués, Josep; Potin-Gautier, M. (CSIRO Publishing, 2015)An on-site methodology has been developed for the direct determination of free Zn2+ with AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) in freshwaters. This implementation includes: i) the use of screen ...