A Production-Accessible Method: Spectrophotometric Iron Speciation in Wine Using Ferrozine and Ethylenediaminetetraacetic Acid

Wine oxidation is reported to be linked to the iron species present in the wine, but spectrophotometric speciation is plagued by unstable measurements due to alterations to the reduction potential of iron by complexing agents. Ferrozine raises the reduction potential of iron by complexing preferentially to iron(II), inducing the reduction of iron(III) during analysis; here, EDTA is added to chelate iron(III) and to stabilize the forms of iron. Bisulfite addition allows the use of ferrozine for red wine analysis by mitigating color interference. Measurements agree with values from a previous method for iron(II) and from FAAS for total iron. Spike recoveries were in the range of 103.5-110.1%. The method is linear for iron concentrations in the range of 0.10-6.00 mg L-1 and offers good precision (CV 0.4-10.1%) and low limits of detection (0.02 mg L-1) and quantification (0.06 mg L-1). The method demonstrated changes to iron speciation during the oxygenation of red wines.