DETERMINATION OF MINERALS AND TRACE-ELEMENTS IN SELENIUM TEA FROM THE ENSCHI DISTRICT, PEOPLES-REPUBLIC-OF-CHINA, AND IN ITS INFUSIONS BY ICP-AES, GFAAS AND INAA

The Enschi district in Hubei province, Peoples Republic of China is geochemically one of the two seleniferous regions, producing both selenium (Se) black tea and the Se green tea. Three samples of green tea with different Se contents and one non-Se tea were analysed. The following mineral and trace elements were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES): K, Ca, Mg, Na, P, S, Al, Mn, Fe, Ba, Sr, Co, Ni, Cu, Zn, Mo, and Cr. Except for Mo, Co, and Cr, all other elements in infusions of the samples analysed were also measured, since their concentrations are lying over their detection limits. The Se content in the tea samples and in the infusions were measured with graphite furnace atomic absorption spectrometry (GFAAS). The accuracy of Se determination was tested by measuring untreated tea samples with instrumental neutron activation analysis (INAA). The Se content in the measured samples was 1 to 8.5 mug/g. In addition to Se, 17 other elements were measured in the tea samples and 14 others in the infusions. With this data the extractible part of this elements in the infusion were calculated. Up to 10% of the Se was found in a first infusion.