ISO 19563:2017 pdf download.Determination of theanine in tea and instant tea in solid form using high-performance liquid chromatography
1 Scope
This document specifies a high-performance liquid chromatographic (HPLC) method for the determination of theanine content in tea (Camellia sinensis). It is applicable to both tea and instant tea samples. Separation of L- and D-theanine is not possible using this method; however, the L-enantiomer is the major form in tea.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 1572, Tea — Preparation of ground sample of known dry matter content
ISO 1573, Tea — Determination of loss in mass at 103 °C
ISO 1839, Tea — Sampling
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 7513, Instant tea in solid form — Determination of moisture content (loss in mass at 103 °C)
ISO 7516, Instant tea in solid form — Sampling
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
4 Principle
A reversed-phase (RP)-C18 column is used which is capable of separating more polar compounds using water as an eluent and UV detection at 210 nm. Theanine is separated from the other amino acids; however, the potential co-elution of theanine with methionine is not relevant due to the very small concentration of methionine in tea. It is recommended that polyamide column extract clean-up is used to remove interfering polyphenols for column protection when separation of theanine from other constituents in the extract sample is difficult. Alternatively, the column should be washed after each tea sample using acetonitrile.
5 Reagents
Use only reagents of recognized analytical grade, unless otherwise specified.
5.1 Water, conforming to grade 1 of ISO 3696.
5.2 Acetonitrile, HPLC grade (however, super grade is preferable).
5.3 Methanol, regular laboratory distilled grade.
5.4 Polyamide (Polyamide CC 6 1) , Particle size: 0,05 mm to 0,16 mm for column chromatography).
5.5 L-theanine reference standard, >99 %, anhydrous.
5.6 HPLC mobile phases.
WARNING — Wear gloves and eye protection and dispense reagents in a fume cupboard.
5.6.1 Mobile phase A, 100 % purified water (5.1).
5.6.2 Mobile phase B, 100 % acetonitrile (5.2).
ISO 19563:2017 pdf download
