Determination of Iron, Copper and Manganese in Wine by Tandem Solid Phase Extraction and Atomic Absorption Spectroscopy
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Abstract:
A rapid and accurate method for the speciation analysis of iron (Fe), copper (Cu) and manganese (Mn) in wine was developed using a tandem column solid phase extraction (SPE) and an atomic absorption spectrometry (AAS). The optimization of SPE conditions, and the effects of pH values (3.00~4.00) and organic acids (single or blend) on recovery rates of metal fraction were investigated in wine-like solutions. Under the optimized activation conditions and flow rate (1 mL/min) of Polyclean X-HLB column linking the column of Superclean SCX at a flow rate of 2 mL/min, these metals were efficiently fractionated into hydrophobic, cationic and residual forms, with a subsequent direct determination of metal ions by graphite furnace AAS. The limit of detection for Fe, Cu and Mn was from 0.39 to 1.56 μg/L, obtaining the recoveries from 90.53% to 112.18%, with the relative standard deviation between 0.89% and 7.12%, suggesting the assay is sensitive with good reproducibility. In aqueous alcoholic solutions, significant effects of pH and organic acids on the distribution of ferric and cupric ions were observed, while few effects were found for manganous (II) ion. In real wine samples, the distributions of Fe, Cu or Mn were different between white and red wines, and were affected by chemical components and the redox state of a wine, present with the predominant residual (Fe, Mn) or hydrophobic (Cu) form.
