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A straightforward method is presented for the operational fractionation of Mn and Zn in beer based on use of a tandem ion exchange column assemblage. Degassed beer samples were driven through the system comprising the weak anion exchanger Reillex 402 (first column) connected in a series with the strong cation exchanger Dowex 50Wx4 (second column). The relevant metal groupings retained on the exchangers, i.e., the fraction of the metals bound to the polyphenols, and the fraction of the cationic metal species, were determined respectively in the effluents (5-mL portions) sampled during the passage of the samples through the first column, and in the eluates obtained by the elution of Mn and Zn species (with 10 mL of 4.0 mol L−1 HCl) from the second column, after passing the samples through the tandem column system. Additionally, the effluents obtained after loading the tandem column system with the samples were also collected and taken to the analysis in order to asses the donation of the third, residual fraction. The usefulness of the fractionation scheme is illustrated by the analysis of three bottled beers produced by a local brewery. The fractionation patterns established for Mn and Zn are discussed regarding the possible associations of the metals under consideration with different endogenous beer ligands. [ABSTRACT FROM AUTHOR]

Abstract: The fractionation pattern of Mn and Zn in the infusions of black and green teas was studied using the Amberlite XAD7 and the Dowex 50Wx4 sorbents connected in a series, after the thorough examination of the sorption and the desorption characteristics of the resins applied. Under the optimized conditions, the one step two column approach developed enabled to distinguish three different operationally defined classes of the metal species, namely the polyphenolic, the cationic and the residual metal fractions. The results indicate that Mn and Zn in tea infusions are predominantly present in the form of the cationic species (up to 80% or more, especially in the green teas). Both metals are also attached to the polyphenolic compounds and possibly to other macromolecules. [Copyright &y& Elsevier]

Abstract: In the present article, a method of operational fractionation of Mn and Zn in beer using flame atomic absorption spectrometry was developed. The proposed fractionation scheme was based on use of a hydrophobic adsorbing resin Amberlite XAD7 (first column, 2g resin bed) connected in a series with a strong cation exchanger Dowex 50Wx4 (second column, 1g resin bed). After passing the samples of beers through the columns, distinct groupings of Mn and Zn species retained on the sorbents, i.e., hydrophobic fraction of polyphenols bound metal species and cationic metal species fraction, respectively, were determined in respective eluates obtained after complete recovery of Mn and Zn species with 10ml of 2.0moll−1 HNO3 (first column) and 10ml of 4.0moll−1 HCl (second column). In addition, the effluents collected were analyzed prior to the evaluation of the third, residual fraction, presumably attributed to any hydrophilic anionic and inert metal species. The established fractionation patterns for Mn and Zn were discussed in reference to likely associations of metals with endogenous food bioligands and possible availability of the distinguished metal species classes. The quality of the results was proved by the recovery experiments. [Copyright &y& Elsevier]