Variation of Trace Element Contents in Black Tea Infusion

Abstract

Contents of 12 trace elements (Na, Fe, Al, Zn, Mn, Cu, Ni, Cr, Se, As, Hg, Pb) in 30 black tea infusion samples were measured by inductively coupled plasma spectrometry or inductively coupled plasma mass spectrometry. The 30 tea samples consisted of Indian tea (9 samples), Ceylon tea (5 samples), Chinese tea (6 samples), Taiwan tea (3 samples), African tea (4 samples) and others (3 samples). The content of each element was as follows (mean±SD):Na, 2.19±2.33ppm; Fe, 0.077±0.036ppm; Mn, 3.83±2.31; Zn, 0.249±0.113 ppm; Al, 3.44±2.18ppm; Ni, 0.040±0.020 ppm; Cr, 0.002 ± 0.003 ppm; Cu, 0.042± 0.023 ppm; As, 1.52±2.31ppb; Hg, 0.027±0.021ppb; Se, 0.55±0.51ppb; Pb, 3.38±3.26 ppb. A regional variation was observed in Na and As contents; African tea showed higher Na contents and Chinese tea showed higher As values than other samples. Factorial analysis showed that the 12 elements were classified 3 groups; elements to belong to the same group showed a similar variation in their concentrations in the tea infusion each other. One group consisted of Mn, Zn, Al, Ni, Cr and Cu, and another group consisted of Fe, Se, As, Hg and Pb. Variation of Na was independent of those of other elements.