This document specifies a high-performance liquid chromatographic (HPLC) method for the determination of theanine content in tea (Camellia sinensis). It is applicable to both tea and instant tea samples. Separation of L- and D-theanine is not possible using this method; however, the L-enantiomer is the major form in tea.st edition 2017-01 Determination of theanine in tea and instant tea in solid form using high- performance liquid chromatography Détermination de la théanine dans le thé et le thé instantané sous forme solide en utilisant la chromatographie en phase liquide à haute performance Reference number ISO 19563:2017(E) ？ ISO 2017 ISO 19563:2017(E) COPYRIGHT PROTECTED DOCUMENT ？ ISO