Theanine is a kind of amino acid contained in tea and has mainly anti-stress and relaxation effects. The analysis of theanine in commercially available supplements was performed in HILIC mode using Asahipak NH2P-50 4E. A calibration curve with high linearity was obtained in the concentration range of 0.001 to 1 mg/mL, and the recovery rate was confirmed to be good at approximately 90 %.
(Pretreatment for sample solution of commercial supplement)
(1) Add 5 mL eluent to 5 mg sample and sonicate for 10 minutes
(2) Filtrate the supernatant with a 0.45 μm filter
Sample : 20 μL
1. Theanine 0.1 mg/mL
Column : Shodex Asahipak NH2P-50 4E (4.6 mm I.D. x 250 mm) Eluent : 20 mM NaH2PO4 + 30 mM H3PO4 aq./CH3CN=25/75 Flow rate : 1.0 mL/min Detector : UV (210 nm) Column temp. : 30 °C