Speciation of Zn, Fe, Ca and Mg in wine with the Donnan Membrane Technique

Publication date: 15 January 2018
Source:Food Chemistry, Volume 239
Author(s): Mireia Lao, Encarnació Companys, Liping Weng, Jaume Puy, Josep Galceran
Free concentrations of Zn²⁺, Fe³⁺, Ca²⁺ and Mg²⁺ in a red wine (Raimat, Catalonia, Spain) have been determined, with the Donnan Membrane Technique (DMT) for the first time. The required equilibration time benefits from the acceptor solution including major cations. K⁺ and Na⁺, mainly unbound to any ligand in the sample, have been identified as suitable reference ions. A free Zn concentration of 1.76μmolL⁻¹ determined with DMT was in excellent agreement with the free Zn concentration independently provided by the electroanalytical technique Absence of Gradients and Nernstian Equilibrium Stripping (AGNES), 1.7μmolL⁻¹, amounting to 14.4% of the total Zn. The free concentrations found in this wine were 1.79μmolL⁻¹ Fe³⁺, 1.11mmolL^–1 Ca²⁺ and 3.4mmolL⁻¹Mg²⁺ (8.82%, 40% and 57% of their total concentrations). Prior to the application of the techniques to the red wine, they had been cross-validated in Zn-tartrate solutions.



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