This standard specifies the principle, instruments and utensils, determination steps and result calculation methods for the determination of water-soluble ash and water-insoluble ash in tea. This standard is applicable to the determination of water-soluble ash and water-insoluble ash in tea. GB/T 8307-2002 Determination of water-soluble ash and water-insoluble ash in tea GB/T8307-2002 Standard download decompression password: www.bzxz.net

GB/T8307--2002
This standard is a revision of GB/T8307-1987 "Determination of water-soluble ash and water-insoluble ash of tea". This standard is equivalent to ISO1576:1988 "Tea - Determination of water-soluble ash and water-insoluble ash". The main differences between this standard and ISO1576:1988 are: the mass of the sample is 2, and the total volume of the water washing paint solution in the main steamer of the determination liquid is 150ml
This standard is revised mainly in accordance with the requirements of GB/T1.11993 "Guidelines for Standardization Work Unit 1: Drafting and Expression Rules of Standards Part 1: Basic Regulations for Standardization Writing", and some modifications have been made to the format and text of GBT8307-1987, but the specific technical content has not changed.
This standard will replace GB/T8307-1987 from the date of implementation. This standard was proposed by the All-China Federation of Supply and Marketing Cooperatives. This standard is under the jurisdiction of Hangzhou Tea Research Institute of China National Federation of Supply and Marketing Cooperatives. Drafting unit of this standard: Hangzhou Tea Research Institute of China National Federation of Supply and Marketing Cooperatives. Main drafters of this standard: Guan Huixian, Sha Haitao. Hangzhou Tea Research Institute of China National Federation of Supply and Marketing Cooperatives is responsible for the interpretation of this standard. 125
GB/T8307-2002
ISO Foreword
International Organization for Standardization (ISO) is a world federation composed of ISO member groups of various international standardization organizations. The work of formulating international standards is usually completed by the technical committee of ISO. Member groups interested in the work of a technical committee have the right to participate in the technical committee. Other international organizations, whether official or unofficial, also participate in its work through liaison with ISO. After the international standard is approved by the ISO committee meeting, the draft international standard is formally adopted by the technical committee and submitted to the member groups for voting. The ISO procedure requires at least 75% of the member groups participating in the voting to agree before it can be formally adopted. International Standard ISO1576 was formulated by ISO/TC34 Agricultural Products Technical Committee. This second revised edition replaces the first edition of ISO 1576:1975, which has been slightly revised. 126
1 Scope
National Standard of the People's Republic of China
Tea--Determination of water-soluble ash and water-insoluble ash content GB/T 8307—2002
eqISO1576:1988
Replaces GB/T83071987
This standard specifies the principle, instruments and utensils, determination steps and result calculation methods for the determination of water-soluble ash and water-insoluble ash in tea.
This standard is applicable to the determination of water-soluble ash and water-insoluble ash in tea. 2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. At the time of publication of this standard, 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/T8306-2002 Determination of total ash in tea
3 Definitions
This standard adopts the following definitions.
3.1 Water-soluble ash water-soluble ash The part of total ash that is soluble in water under specified conditions. 3.2 Water-insoluble ash water-insoluble ash The part of total ash that is insoluble in water under specified conditions. 4 Principle
Total ash is extracted with hot water, filtered through ash-free filter paper, burned, and the residue is weighed to determine the water-insoluble ash: the water-soluble ash is calculated from the difference in mass between the total ash and the water-insoluble ash. 5 Instruments and appliances
Routine laboratory instruments and the following items:
5.1 Floor cradle: porcelain, high type, capacity 30mlL. 5.2 Electric heating plate.
5.3 High temperature electric furnace: 525C ± 25C.
5.4 Crucible tongs.
5.5 Water bath.
5.6 Desiccant: filled with effective desiccant.
5.7 Analytical balance: sensitivity 0.001.g.
Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on June 17, 2002, implemented on December 1, 2002
5.8 Ash-free filter paper.
6 Determination steps
6.1 Sampling
According to the provisions of GB/T8302.
6.2 Sample preparation
According to the provisions of GB/T8303.
6.3 Total ash preparation
According to the provisions of GB/T8306.
6.4 Determination
GB/T 8307—2002Www.bzxZ.net
Use 25mL hot distilled water to wash the ash into a 100mL beaker. Heat to a slight boil (splash-proof), filter with ash-free filter paper while hot, and wash the residue on the beaker and filter paper with hot distilled water repeatedly until the volume of the filtrate and washing liquid reaches 150mL. Transfer the filter paper and the residue into the original crucible, and carefully evaporate the water in a boiling water bath. Move it into a high-temperature furnace and burn it at 525℃±25C until there is no carbon particles in the ash (about 1h). When the furnace temperature drops to about 300℃, take out the crucible, cool it to room temperature in a desiccator, and weigh it. Move it into the high temperature furnace and burn for 30 minutes, take out the crucible, cool and weigh it. Repeat this operation until the difference between two consecutive weighings does not exceed 0.001g, which is the constant weight. The minimum weighing shall prevail.
6.5 Others
If necessary, retain the filtrate to determine the alkalinity of water-soluble ash. 7 Result calculation
7.1 Calculation method
7.1.1 Water-insoluble ash
The water-insoluble ash in tea leaves is expressed as dry mass fraction and calculated according to formula (1): M1-M2×100
Water-insoluble ash (%)=
M. Xm
Where: M,---the mass of the crucible and water-insoluble ash, g; the mass of the crucible, g;
M. The mass of the sample.g;
The dry matter content of the sample, %.
7.1.2 Water-soluble ash
The water-soluble ash in tea, expressed as dry mass fraction, is calculated according to formula (2): Water-soluble ash (%) -
Mass of total ash, g;
Wherein: M -
Mass of water-insoluble ash, g,
Mass of sample, g;
mDry matter content of sample, %.
M, - M2
M. Xm
7.1.3 If the requirements of repeatability (7.2) are met, take the arithmetic mean of the two measurements as the result (keep one decimal place). 7.2 Repeatability
The difference between the two measured values ​​of the same sample shall not exceed 0.2g for every 100g of sample. 128
(2)
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