Direct ICP-OES multielement analysis of infused black and green teas and chemical fractionation of selected essential and non-essential elements prior to evaluation of their bioavailability and classification of teas by pattern recognition

Abstract

Operationally defined chemical fractionation of Al, Ba, Ca, Cu, Fe, Mg, Mn, Ni, Sr and Zn in infusions of loose leaf and bagged black and green teas was carried out. It was based on tandem-column solid phase extraction using reverse-phase and strong cation-exchange extraction tubes connected in series. Concentrations of elements in resultant infusions as well as column effluents and eluates were determined with the aid of inductively coupled plasma optical emission spectrometry and a newly developed simplified sample preparation procedure. It was established that information on separated chemical fractions, particularly the fraction of residual species of elements, had better discrimination power than information about total concentrations of these elements. Differences in chemical fractionation patterns of elements in infusions of analyzed four types of tea led to simple classification of different black and green teas by principal component analysis and linear discriminant analysis. Keywords: Infusions, Black tea, Green tea, Elements, Solid phase extraction, Chemical fractionation