Quality control of commercial tea by x‐ray fluorescence

Abstract

Abstract Based on the energy‐dispersive x‐ray fluorescence (EDXRF) technique, the concentrations of elements (22 ≤ Z ≤ 30) were assessed in five kinds of commercial tea from six commercial suppliers: Matricaria chamomilla L. (camomile), Mentha piperita L. (mint), Cymbopogon citratus (DC) Stapf. (herb ‘cidreira’), Malus domestica Borkh. (apple tea) and Camellia sinensis (L.) O. Kuntze (black tea). The samples were excited by an x‐ray tube with an Mo anode (25 kV and 10 mA), with a Zr filter, and the characteristic x‐ray were detected by an Si(Li) detector coupled to a multichannel analyzer. Using standard samples, the relationship between the detection limit and the atomic numbers of Fe, Co, Ni, Cu and Zn was determined. In some tea samples Ti was detected, but it is not an essential microelement for the plant growth. Fe, Ni and Cu were detected in all tea samples analyzed; Ti, Cr, Co and Zn were detected in Matricaria chamomilla and Malus domestica ; Ti, Co and Zn in Mentha piperita and Ti, Mn, Co and Zn in Cymbopogon citratus . The inorganic constitution profile of this matrix type and the fingerprints in the production process can be evaluated by employing the EDXRF quality control of the commercial products. Copyright © 2002 John Wiley & Sons, Ltd.