Chemical fractionation of Cu, Fe and Mn in canned Polish beers

A dual-column solid-phase extraction (SPE) was applied to study the distribution of Cu, Fe and Mn among the species of different charge and hydrophobicity in canned Polish lager-type beers. In addition, an original open vessel wet digestion method, aimed at decreasing the reagent amounts and the decomposition time, was devised for the determination of the total Cu, Fe and Mn concentrations in the analyzed beers by means of air–acetylene flame atomic absorption spectrometry (F-AAS) and compared with the method of direct beer analysis. To separate distinct Cu, Fe and Mn species, 50-mL portions of degassed beers were passed through a column containing a non-ionic adsorbing resin Amberlite XAD-16, and then the effluents from this column were directly driven through the second column filled with a gel-type strong cation exchange resin Dowex 50W-x4-200. The content of Cu, Fe and Mn was determined in the effluents from both columns, and the eluates from the cation exchanger column achieved by passing 10 mL of a 2 mol L−1 HCl solution through its resin bed. It yielded the discrimination of the phenolic bound, the cationic and the residual species fractions of Cu, Fe and Mn in the beers studied. The results obtained were discussed with reference to the related literature and interpreted concerning possible classes of compounds capable of complexing Cu, Fe and Mn in the beer matrix.