GB/T 21727-2008 English PDF (GB/T21727-2008)

GB/T 21727-2008: Instant tea in solid form -- Determination of catechins content
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GB/T 21727-2008
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 67.140.10
X 04
Instant tea in solid form - Determination of catechins
content
(ISO 14502-2:2005, Determination of substances characteristic of green and
black tea - Part 2: Content of catechins in green tea - Method using high-
performance liquid chromatography, MOD)
ISSUED ON: MAY 04, 2008
IMPLEMENTED ON: OCTOBER 01, 2008
Issued by: General Administration of Quality Supervision, Inspection
and Quarantine;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Principle ... 4 
4 Apparatus ... 4 
5 Reagents ... 5 
6 Operating methods ... 6 
7 Result calculation ... 7 
Instant tea in solid form - Determination of catechins
content
1 Scope
This Standard specifies the determination of catechins content in instant tea in
solid form by high-performance liquid chromatography (HPLC).
This Standard applies to the determination of catechins content in instant tea in
solid form.
2 Normative references
The terms in the following documents become the terms of this Standard by
reference to this Standard. For dated references, all subsequent amendments
(not including errata content) or revisions do not apply to this standard. However,
parties to agreements that are based on this Standard are encouraged to study
whether the latest versions of these documents can be used. For undated
references, the latest edition applies to this Standard.
GB/T 18798.1, Instant tea in solid form - Part 1: Sampling (GB/T 18798.1-
2002, eqv ISO 7516:1984)
GB/T 18798.3, Instant tea in solid form - Part 3: Determination of moisture
content (GB/T 18798.3-2002, eqv ISO 7513:1990)
3 Principle
Instant teas are dissolved in hot water with 10% acetonitrile. The catechins are
determined by HPLC on a C18 column using gradient elution with UV detection
at 278 nm. External standards of catechin standards are used for quantitation
directly; alternatively, caffeine may be used as a standard in conjunction with
individual catechin Relative Response Factors (RRFStd) established by an ISO
international interlaboratory test (see 7.2).
4 Apparatus
4.1 Analytical balance: sensitivity of 0.000 1 g.
4.2 Water bath.
5.9.2 Gallic acid (GA) stock standard solution: 0.100 mg/mL.
5.9.3 Catechin stock standard solutions: +C 1.00 mg/mL, +EC 1.00 mg/mL,
+EGC 2.00 mg/mL, +EGCG 2.00 mg/mL, +ECG 2.00 mg/mL.
5.10 Standard working solution: use the stabilizing solution (5.7) to prepare.
Concentrations of standard working solutions: gallic acid 5 μg/mL ~ 25 μg/mL,
caffeine 50 μg/mL ~ 150 μg/mL, +C 50 μg/mL ~ 150 μg/mL, +EC 50 μg/mL ~
150 μg/mL, +EGC 100 μg/mL ~ 300 μg/mL, +EGCG 100 μg/mL ~ 400 μg/mL,
+ECG 50 μg/mL ~ 200 μg/mL.
6 Operating methods
6.1 Sampling
In accordance with the provisions of GB/T 18798.1.
6.2 Determination steps
6.2.1 Determination of dry matter content
In accordance with the provisions of GB/T 18798.3.
6.2.2 Preparation of test solution
Weigh 0.5 g (accurate to 0.000 1 g) of uniform instant tea into a 50 mL
volumetric flask; add water of ≤60 °C to dissolve; add 5 mL of acetonitrile (5.1);
use water to dilute to the mark; shake well. Use a pipette to transfer 2 mL of the
above extraction solution to a 10 mL volumetric flask; use the stabilizing solution
(5.7) to dilute to the mark; shake well; pass through a 0.45 μm membrane, for
later measurement.
6.2.3 Chromatographic conditions
Mobile phase flow rate: 1 mL/min.
Column temperature: 35 °C.
Ultraviolet detector: λ = 278 nm.
Gradient conditions: Keep at 100% phase A for 10 min
From 100% phase A → 68% phase A, 32% phase B within
15 min
GB/T 21727-2008
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 67.140.10
X 04
Instant tea in solid form - Determination of catechins
content
(ISO 14502-2:2005, Determination of substances characteristic of green and
black tea - Part 2: Content of catechins in green tea - Method using high-
performance liquid chromatography, MOD)
ISSUED ON: MAY 04, 2008
IMPLEMENTED ON: OCTOBER 01, 2008
Issued by: General Administration of Quality Supervision, Inspection
and Quarantine;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Principle ... 4 
4 Apparatus ... 4 
5 Reagents ... 5 
6 Operating methods ... 6 
7 Result calculation ... 7 
Instant tea in solid form - Determination of catechins
content
1 Scope
This Standard specifies the determination of catechins content in instant tea in
solid form by high-performance liquid chromatography (HPLC).
This Standard applies to the determination of catechins content in instant tea in
solid form.
2 Normative references
The terms in the following documents become the terms of this Standard by
reference to this Standard. For dated references, all subsequent amendments
(not including errata content) or revisions do not apply to this standard. However,
parties to agreements that are based on this Standard are encouraged to study
whether the latest versions of these documents can be used. For undated
references, the latest edition applies to this Standard.
GB/T 18798.1, Instant tea in solid form - Part 1: Sampling (GB/T 18798.1-
2002, eqv ISO 7516:1984)
GB/T 18798.3, Instant tea in solid form - Part 3: Determination of moisture
content (GB/T 18798.3-2002, eqv ISO 7513:1990)
3 Principle
Instant teas are dissolved in hot water with 10% acetonitrile. The catechins are
determined by HPLC on a C18 column using gradient elution with UV detection
at 278 nm. External standards of catechin standards are used for quantitation
directly; alternatively, caffeine may be used as a standard in conjunction with
individual catechin Relative Response Factors (RRFStd) established by an ISO
international interlaboratory test (see 7.2).
4 Apparatus
4.1 Analytical balance: sensitivity of 0.000 1 g.
4.2 Water bath.
5.9.2 Gallic acid (GA) stock standard solution: 0.100 mg/mL.
5.9.3 Catechin stock standard solutions: +C 1.00 mg/mL, +EC 1.00 mg/mL,
+EGC 2.00 mg/mL, +EGCG 2.00 mg/mL, +ECG 2.00 mg/mL.
5.10 Standard working solution: use the stabilizing solution (5.7) to prepare.
Concentrations of standard working solutions: gallic acid 5 μg/mL ~ 25 μg/mL,
caffeine 50 μg/mL ~ 150 μg/mL, +C 50 μg/mL ~ 150 μg/mL, +EC 50 μg/mL ~
150 μg/mL, +EGC 100 μg/mL ~ 300 μg/mL, +EGCG 100 μg/mL ~ 400 μg/mL,
+ECG 50 μg/mL ~ 200 μg/mL.
6 Operating methods
6.1 Sampling
In accordance with the provisions of GB/T 18798.1.
6.2 Determination steps
6.2.1 Determination of dry matter content
In accordance with the provisions of GB/T 18798.3.
6.2.2 Preparation of test solution
Weigh 0.5 g (accurate to 0.000 1 g) of uniform instant tea into a 50 mL
volumetric flask; add water of ≤60 °C to dissolve; add 5 mL of acetonitrile (5.1);
use water to dilute to the mark; shake well. Use a pipette to transfer 2 mL of the
above extraction solution to a 10 mL volumetric flask; use the stabilizing solution
(5.7) to dilute to the mark; shake well; pass through a 0.45 μm membrane, for
later measurement.
6.2.3 Chromatographic conditions
Mobile phase flow rate: 1 mL/min.
Column temperature: 35 °C.
Ultraviolet detector: λ = 278 nm.
Gradient conditions: Keep at 100% phase A for 10 min
From 100% phase A → 68% phase A, 32% phase B within
15 min