研究目的
To develop a simple spectrophotometric method for iron speciation in both white and red wines with minimal disturbance of wine conditions, stabilization against redox drift of iron species during analysis, allowing for single-point measurements, and utilization of reagents and equipment accessible in a wine production environment.
研究成果
The proposed spectrophotometric method using ferrozine and EDTA effectively stabilizes iron speciation in wine, preventing redox drift and enabling accurate measurements. It agrees with previous methods and FAAS, shows good precision, low detection limits, and high spike recoveries. The method is accessible for wineries and useful for monitoring iron speciation during processes like oxygenation, providing insights into wine oxidation dynamics. Future studies should explore its application in environmental samples and further investigate the mechanisms of iron complexation.
研究不足
The method may be affected by interference from other metals like copper, magnesium, and calcium that form colored complexes with ferrozine. The effectiveness of bisulfite in mitigating color interference depends on the wine's chemical composition and age, with potential issues in older wines due to resistant pigments. The stability constants for iron complexes in wine matrices were not quantitatively determined, and electrochemical measurements of reduction potential were not conducted due to interference from ethanol oxidation.
1：Experimental Design and Method Selection:
The study designed a spectrophotometric method using ferrozine and EDTA to stabilize iron species, with bisulfite added for red wines to mitigate color interference. The rationale was to prevent redox drift and enable single-point measurements.
2：Sample Selection and Data Sources:
White and red wine samples were donated or produced by the Department of Viticulture and Enology at the University of California, Davis. Model wine was prepared with ethanol and tartaric acid.
3：List of Experimental Equipment and Materials:
Equipment included an Agilent Technologies 8453 spectrophotometer, Varian SpectrAA 220 flame atomic absorption spectrometer, Innova 2300 platform shaker, and disposable acrylic cuvettes. Materials included ferrozine, EDTA, ascorbic acid, sodium metabisulfite, tartaric acid, ferrous sulfate heptahydrate, ferric chloride hexahydrate, hydrochloric acid, sodium hydroxide, and ethanol.
4：Experimental Procedures and Operational Workflow:
For iron(II) determination in white wine, 1000 μL of wine was mixed with 10 μL of ferrozine solution, then 1500 μL of EDTA solution was added, and absorbance measured at 562 nm after 1 min. For red wines, 250 μL of wine was used with 750 μL sodium metabisulfite added after EDTA, and measurements taken after stabilization (up to 15 min). For total iron, EDTA was replaced with ascorbic acid solution, and measurements taken after stabilization (up to 30 min). Background absorbance corrections were applied.
5：Data Analysis Methods:
Data were analyzed using linear least-squares regression in Microsoft Excel for calibration curves, correlation coefficients, and t-tests. Precision was assessed via coefficients of variation, and limits of detection and quantification were calculated based on IUPAC recommendations.
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