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)
1. Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology, , Yokohama, Kanagawa, 226‐8503 Japan;2. National Institute of Vegetable and Tea Science, , Shizuoka, 428‐8501 Japan