Analytical Sciences
Online ISSN : 1348-2246
Print ISSN : 0910-6340
ISSN-L : 0910-6340
Original Papers
Comparison of Heating Extraction Procedures for Al, Ca, Mg, and Mn in Tea Samples
Letícia M. COSTASandro T. GOUVEIAJoaquim A. NÓBREGA
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2002 Volume 18 Issue 3 Pages 313-318

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Abstract

A focused-microwave-assisted procedure was adopted for the extraction of Al, Ca, Mg, and Mn in tea leaves. The efficiency of extraction was evaluated using diluted acids and a water-soluble alkaline tertiary-amines solution. The extraction procedure was implemented in 5 min. A conventional hot-plate digestion procedure was employed for a comparison. A colorless digest was obtained for all tea samples and the total contents determined for each analyte were employed for estimating the efficiency of extraction. Tea infusions were also prepared. Subsequent determinations of Al, Ca, Mg, and Mn were carried out using flame atomic absorption spectrophotometry (FAAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). In most cases, quantitative, or at least semi-quantitative, extractions were attained for Ca, Mg, and Mn. Lower recoveries were attained to Al, which seems to be related to compounds that bind this element in the sample matrix. Large variations in the trace-element composition of teas were observed; these results are discussed with reference to both extraction media and type of tea.

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© 2002 by The Japan Society for Analytical Chemistry
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