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An LC-ESI/MS Method for Determining Theanine in Green Tea Dietary Supplements



Mary Bedner, Lane C. Sander, Katherine E. Sharpless


Theanine is the major amino acid present in Camellia sinensis, or green tea. A method for determining theanine in its native state using liquid chromatography with positive-mode electrospray ionization mass spectrometric detection was developed. Quantitation of theanine was achieved using isotope dilution with labeled theanine as an internal standard. This approach was utilized on different green tea matrix materials that are commonly used as dietary supplements including powdered plant leaves, a powdered plant leaf extract, and an oral dosage form that contains green tea. Excellent measurement precision was obtained for all three materials using the developed method. The theanine response was linear over several orders of magnitude, and the calculated limit of detection and limit of quantitiation were 0.5 ng and 1.5 ng, respectively.
Analytical and Bioanalytical Chemistry


Theanine, green tea, Camellia sinensis, liquid chromatography, mass spectrometry, standard reference material


Bedner, M. , Sander, L. and Sharpless, K. (2010), An LC-ESI/MS Method for Determining Theanine in Green Tea Dietary Supplements, Analytical and Bioanalytical Chemistry, [online], (Accessed July 14, 2024)


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Created April 28, 2010, Updated February 19, 2017