ISO 18447:2021
Tea — Determination of theaflavins in black tea — Method using high performance liquid chromatography
This document specifies a high performance liquid chromatography (HPLC) or ultra-high performance liquid chromatography (UHPLC) method for the determination of content of the four major theaflavins of tea.
It is applicable to both leaf and instant black and oolong teas. The method is currently not validated for ready-to-drink (RTD) beverages.
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Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Principle
5 Reagents
5.1 General
5.2 HPLC mobile phases
5.3 Stock standard solutions
5.3.1 General
5.3.2 Preparation of individual theaflavin stock standard solutions
5.4 Mixed standard solutions
5.5 Caffeine standard — Preparation of caffeine stock solution, corresponding to 2,00 mg/ml
6 Apparatus
7 Sampling
8 Preparation of test samples
9 Procedure
9.1 General
9.2 Determination of dry matter content
9.3 Test portion
9.3.1 Instant tea
9.3.2 Leaf tea
9.4 Extraction of theaflavins
9.4.1 Instant tea
9.4.2 Leaf tea
9.5 Dilution
9.6 Determination
9.6.1 General
9.6.2 Adjustment of the apparatus
9.6.3 HPLC analysis
9.6.4 Identification
10 Calculation
10.1 General
10.2 Quantitation using theaflavin standards
10.3 Quantitation using a caffeine standard and theaflavin RRFs
11 Precision
11.1 Interlaboratory test
11.2 Repeatability
11.3 Reproducibility
12 Test report
Annex A (informative) Results of interlaboratory tests
Annex B (informative) Assessment of the purity of standards used in the RRF work
Annex C (informative) Typical HPLC chromatograms
Bibliography
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Related Information
Similar Standards
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BS 5987:1980
Methods for sampling tea
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BS 6049-1:1981
Methods of test for tea, Preparation of ground sample of known dry matter content
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BS 6049-2:1981
Methods of test for tea, Determination of loss in mass at 103°C
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BS 6049-3:1994
Methods of test for tea, Determination of water extract
Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Principle
5 Reagents
5.1 General
5.2 HPLC mobile phases
5.3 Stock standard solutions
5.3.1 General
5.3.2 Preparation of individual theaflavin stock standard solutions
5.4 Mixed standard solutions
5.5 Caffeine standard — Preparation of caffeine stock solution, corresponding to 2,00 mg/ml
6 Apparatus
7 Sampling
8 Preparation of test samples
9 Procedure
9.1 General
9.2 Determination of dry matter content
9.3 Test portion
9.3.1 Instant tea
9.3.2 Leaf tea
9.4 Extraction of theaflavins
9.4.1 Instant tea
9.4.2 Leaf tea
9.5 Dilution
9.6 Determination
9.6.1 General
9.6.2 Adjustment of the apparatus
9.6.3 HPLC analysis
9.6.4 Identification
10 Calculation
10.1 General
10.2 Quantitation using theaflavin standards
10.3 Quantitation using a caffeine standard and theaflavin RRFs
11 Precision
11.1 Interlaboratory test
11.2 Repeatability
11.3 Reproducibility
12 Test report
Annex A (informative) Results of interlaboratory tests
Annex B (informative) Assessment of the purity of standards used in the RRF work
Annex C (informative) Typical HPLC chromatograms
Bibliography