Application of the new electroanalytical technique AGNES for the determination of free Zn concentration in river water
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Absence of gradients and Nernstian equilibrium stripping (AGNES) is a recently developed electroanalytical technique specifically designed for the direct determination of free concentrations of metal ions. AGNES is applied here to the determination of free Zn concentration in a river water sample. The method has been validated with synthetic solutions of low ionic strengths containing Zn and 2,6-pyridinedicarboxylic acid and then applied to synthetic river waters and to a natural sample collected from Besòs River in Montcada i Reixac (Catalonia, North-Eastern Spain). In the river sample, an average free Zn concentration of 12.8(4) nM was obtained, while the total dissolved Zn concentration was 0.51(8) μM. To control and maintain pH and pCO2 constant during AGNES measurements, a novel device for N2/CO2 mixed purging has been developed.
KeywordsSpeciation AGNES River water Synthetic water Zn Purging system
We thank M.L. Tercier-Waeber and J. Buffle for detailed information on their N2/CO2 purging device. We acknowledge support of this research from the Spanish Ministry of Education and Science (Project CTQ2006-14385) and from the “Comissionat d’Universitats i Recerca de la Generalitat de Catalunya”. The authors greatly appreciate the financial support of FAR, Fondo Ateneo per la Ricerca, Università di Pavia, Italy.
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