This standard specifies the principle, instruments and utensils, reagents and solutions, operation methods and result calculation methods for the determination of tea polyphenols in tea. This standard is applicable to the determination of tea polyphenols in tea, but not to the determination of tea polyphenols in tea extract products. GB/T 8313-2002 Determination of tea polyphenols GB/T8313-2002 standard download decompression password: www.bzxz.net

GB/T 8313-2002
This standard is a revision of GBT8313--1987 "Determination of Tea Polyphenols".
This revision only makes some changes to the format and text of GB/T8313-1987, and the specific technical content remains unchanged. This standard will replace GB/T8313-1987 from the date of implementation. This standard is proposed by the All-China Federation of Supply and Marketing Cooperatives. This standard is under the jurisdiction of the Hangzhou Tea Research Institute of the All-China Federation of Supply and Marketing Cooperatives. The drafting unit of this standard: Hangzhou Tea Research Institute of the All-China Federation of Supply and Marketing Cooperatives. The main drafters of this standard: Zhou Weilong, Sun Anhua, Zhong Luo. The Hangzhou Tea Research Institute of the All-China Federation of Supply and Marketing Cooperatives is responsible for the interpretation of this standard. 149
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National Standard of the People's Republic of China
Deterrn i nation of tea polyphenols content
Tea--- Deterrn i nation of tea polyphenols contentGB/T 8313—2002
Replaces GB/T8313--1987
This standard specifies the principle, instruments and utensils, reagents and solutions, operation methods and result calculation methods for the determination of tea polyphenols in tea. This standard is applicable to the determination of tea polyphenols in tea, but not to the determination of tea polyphenols in tea extract products. 2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T8302—2002 Tea sampling
GB/T8303--2002 Preparation of ground tea samples and determination of their dry matter content GB/T8312—2002 Determination of caffeine in tea
3 Definitions
This standard adopts the following definitions.
Tea polyphenols
Phenolic compounds in the tea water overflow that react with ferrous ions to form a complex. 4 Principle
Polyphenols in tea can form purple-blue complexes with ferrous ions. Determine their content by spectrophotometry. 5 Instruments and equipment
Routine laboratory instruments and the following items:
5.1 Analytical balance: sensitivity 0.001
5.2 Spectrophotometer.
6 Reagents and solutions
The reagents used should be analytical grade (AR) and the water should be distilled water. 6.1 Ferrous tartrate solution: weigh 1.0g ferrous sulfate (FeSO.7HO) and 5.0g potassium sodium tartrate (CH.OKNa*4H.0), dissolve in water and dilute to 1L (10 days of validity when stored at low temperature). 6.2 pH 7.5 phosphate buffer solution
6.2.1 1/15mol/L disodium hydrogen phosphate: weigh 23.9g disodium hydrogen phosphate dodecahydrate (Na2HPO,*12H2O), dissolve in water and dilute to 1L.
6.2.2 1/15mol/L potassium dihydrogen phosphate: weigh 9.08g potassium dihydrogen phosphate (KHPO) dried at 110C for 2h, dissolve in water and dilute to 1.
GB/T8313—2002
Take 85mL of the above 1/15mol/L disodium hydrogen phosphate solution and 15mL of 1/15mol/L potassium dihydrogen phosphate solution and mix them evenly. 7 Operation method
7.1 Sampling
According to the provisions of GB/T8302.
7.2 Sample preparation
According to the provisions of GB/T8303.
7.3 Determination steps
7.3.1 Test solution preparation
According to the provisions of 11.1 of GB/T8312—2002. 7.3.2 Determination
Accurately pipette 1 ml of the test solution (7.3.1) into a 25-ml volumetric flask, add 4 ml of water and 5 ml of ferrous tartrate solution (6.1), mix thoroughly, then add pH 7.5 phosphate buffer (6.2) to the scale, and measure the absorbance (A) in a 10 mm cuvette at a wavelength of 540 nm, using the reagent solution as a reference.
8 Calculation of results
8.1 Calculation method
The content of tea polyphenols in tea is expressed as dry mass fraction, calculated according to formula (1): A×1.957×2
Tea polyphenols (%)-
Where: L,-total test solution, mL;
L-volume of liquid used in the determination, mL
Mmass of the sample, g
m-dry matter content of the sample, %:
A-absorbance of the sample;
XMX m
1.957~-Using a 10mm colorimetric cup, when the absorbance is equal to 0.50, each milliliter of tea contains 1.957mg of tea polyphenols. If the requirements of repeatability (8.2) are met, the arithmetic mean of the two determinations is taken as the result, and the result is rounded to one decimal place. 8.2 Repeatability
The difference between two measured values ​​of the same sample shall not exceed 0.5g for every 100 samples. 151
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