Evaluation of the total content and the operationally defined species of copper in beers and wines.

A two-column solid phase extraction was used to determine the operationally defined speciation of Cu in lager beers and red wines. Applying a nonionic macroreticular adsorbing resin Amberlite XAD-16 and a gel type strong cation exchange resin Dowex 50Wx8-200, three different groupings of the chemical forms of Cu, including the hydrophobic, the cationic, and the residual species fractions, were separated and determined. The total content of Cu in the analyzed samples and its concentrations in the distinguished fractions were measured using flame atomic absorption spectrometry without any special preparation of the sample solutions. It was found that the residual species (72-82% of the total content), being polar and noncationic forms of Cu, are the most abundant fraction of Cu in the analyzed beers. In the case of wines, the fraction of the hydrophobic species was established to have the highest share in the total Cu content, that is, 27-77%. This fraction was presumed to contain relatively strong complexes of Cu with various flavonoids and other polyphenols.