Measurement of theanine using reverse-phase ion-pair liquid chromatography with photodiode array detection

► A efficient and inexpensive chromatographic method was developed for the detection and quantitation of theanine in tea. ► Sonication is recommended for tea sample preparation, resulting in a rapid, simple sample preparation procedure. ► The purity of the theanine peak in the tea samples was determined by using HPLC-MS. ► The recoveries and RSD values were obtained acceptable for analysis.