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Method Abstracts 378

MA 378 / 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 its known relaxation effect. Theanine also has been proven to reduce physical and mental stress, and improve cognition and mood.

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.

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

METHOD

Sample Preparation

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

Analytical Conditions

Column: High-efficiency Lithium cation-exchange column,
       4.6×75 mm, Catalog number 0354675T
Flow Rate: 0.55 mL/min
Mobile Phase: see methodL
FLD: Excitation 365 nm, Emission 430 nm

Post-Column Conditions

Post-column System: Pinnacle PCX
Reactor Volume: 0.5 mL
Reactor Temperature: 130 °C
Reagent: Trione® Ninhydrin reagent
Flow Rate: 0.3 mL/min
Detection: UV/VIS 570 nm for primary amino acids,
       440 nm for secondary amino acids

HPLC GRADIENT

TIME (Min)

1700-1125, %

Li365, %

Li375, %

RG003, %

0

100

0

0

0

10

1000

0

0

0

19

40

60

0

0

32

0

100

0

0

43

0

100

0

0

43.1 0 0 100 0
57 0 0 100 0
57.1 0 0 70 30
72 0 0 70 30

COLUMN OVEN PROGRAM

TIME (Min)

Temperature, °C

0

34

6

34

17

65

25

70

70

70

71

34

RUN TIME: 72 min
EQUILIBRATION TIME: 12 min


 

M_378

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