High performance liquid chromatography (HPLC) coupled with evaporative light scattering detector ( ELSD-2000 ) was used for the determination of theanine in tea without derivatization. A Polaris-C18 column (250 mm×4.6 mm) was used with the mobile phase of 0.1%trifluoroacetic acid water solution and 0.1% trifluoroacetic acid acetonitrile solution .The flow rate was at 0.5 ml/min. The linear response ranged from 0.062-0.450 mg/mL for theanine. The recovery was 9...