Measurement of Free Zinc Concentration in Wine with AGNES

• Published in: Journal of agricultural and food chemistry Vol. 56; no. 18; pp. 8296 - 8302
• Main Authors: Companys, Encarnació, Naval-Sánchez, Marina, Martínez-Micaelo, Neus, Puy, Jaume, Galceran, Josep
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 24.09.2008
• Subjects: Absence of Gradients and Nernstian Equilibrium Stripping; AGNES; Analytical Methods; Biological and medical sciences; dietary minerals; Electrodes; ethanol; Ethanol - analysis; Fermented food industries; food analysis; food composition; Food industries; free Zn concentration; Fundamental and applied biological sciences. Psychology; heavy metals; measurement; mineral content; Potentiometry - methods; speciation; stripping analysis; Viscosity; Wine; Wine - analysis; wine quality; wines; Wines and vinegars; zinc; Zinc - analysis; Wine; free Zn concentration; AGNES; heavy metals; stripping analysis; ethanol; speciation; Ethanol; Concentration; Inorganic element; Zinc; Heavy metal; Concentration measurement; Alcoholic beverage; Speciation
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf8013475

AGNES (absence of gradients and Nernstian equilibrium stripping), a voltammetric technique recently introduced to measure free metal concentration in solution and checked with different natural and synthetic aqueous media, has been applied here to determine free Zn concentration in wine. The content of ethanol in a solution increases its viscosity, and, so, the diffusion coefficient decreases. Another added effect in ethanolic solutions is the increase of the activity of the metal ions, due to the decrease of the permittivity in the alcoholic medium with respect to the aqueous one. With this taken into account, a specific methodology has been developed to apply AGNES in ethanolic media. A relevant point in this methodology has been the introduction of a new kind of blank, the EDTA blank, able to be applied in the same natural sample and with the same potential program. The free Zn concentrations of the two wines analyzed, a red and a white Raimat wine, were 4.5(2) × 10−7 and 7.2(4) × 10−7 M, respectively. These represent around 5% of the total Zn content. In the wine samples analyzed, it was checked that intermetallic formation of Zn−Cu does not affect the measurement of free Zn in a significant way.