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Development of a methodology using gas chromatography‐combustion‐isotope ratio mass spectrometry for the determination of the carbon isotope ratio of caffeine extracted from tea leaves ( Camellia sinensis )
Author(s) -
Wu Chen,
Yamada Keita,
Sumikawa Osamu,
Matsunaga Akiko,
Gilbert Alexis,
Yoshida Naohiro
Publication year - 2012
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6177
Subject(s) - isotope ratio mass spectrometry , chemistry , caffeine , isotopes of carbon , chromatography , mass spectrometry , isotope , isotope analysis , gas chromatography , carbon fibers , stable isotope ratio , extraction (chemistry) , environmental chemistry , total organic carbon , medicine , ecology , physics , materials science , quantum mechanics , composite number , composite material , biology , endocrinology
RATIONALE Compound‐specific isotope analysis (CSIA) of the extracted caffeine can be used to determine the authenticity of the origin of tea. Elemental analysis‐isotope ratio mass spectrometry (EA‐IRMS), which is widely used to measure the carbon isotope ratio of caffeine, has a strict requirement for the purity of the extracted caffeine. To obtain high‐purity caffeine from tea leaves, the conventional extraction process has to be repeated and usually takes about 5–6 h. To improve the measurement of the carbon isotope ratio of caffeine, a more rapid and accurate measuring method is needed. METHODS An analytical protocol was developed for the determination of the carbon isotope ratio of caffeine from tea leaves using gas chromatography‐combustion‐isotope ratio mass spectrometry (GC‐C‐IRMS) combined with our extraction process. The procedure to extract caffeine and determine its carbon isotope ratio takes around 1.5 h. RESULTS The standard deviation of the method is less than 0.1‰ (1σ). The measured carbon isotope ratios were not influenced by the amount of caffeine injected (0.08–0.62 µg) or by the extraction yield of caffeine from the tea leaves. CONCLUSIONS The carbon isotope ratios of caffeine from eight tea cultivars were determined using the protocol. Copyright © 2012 John Wiley & Sons, Ltd.