Fractionation analysis of manganese and zinc in tea infusions by two-column solid phase extraction and flame atomic absorption spectrometry

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.