Analysis of L-Theanine in Tea by HPLC with Post- Column Derivatization

Theanine is a neurologically active amino acid found in tea plants. L-Theanine is a dominant amino acid in green tea and is responsible for its unique pleasant taste as well as known relaxation effect. Theanine also has been proven to reduce physical and mental stress, and improve cognition and mood.

Table I: Column oven program

Cation-exchange chromatography using post-column Ninhydrin reagent Trione and UV detection has shown unmatched reproducibility and selectivity in the analysis of free amino acids in complex matrices. The Pinnacle PCX post-column derivatization system allows shortening run times by utilizing column temperature gradients.

Table II: HPLC gradient

We introduce a simple and robust method for analysis of L-Theanine in addition to the other free amino acids in tea leaves.

Figure 1: Chromatogram of green tea sample.

Method

Sample Preparation

Homogenize 2 g of dry tea leaves with 25 mL of Li220 for 5 min. Centrifuge and filter through 0.45 µm nylon filter.

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Figure 2: Chromatogram of white tea sample.

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