GB/T 8308-2002 Determination of the insoluble ash of thecacid

This standard specifies the principle, reagents and solutions, instruments and utensils, operation methods and result calculation for the determination of acid insoluble ash in tea. This standard is applicable to the determination of acid insoluble ash in tea. GB/T 8308-2002 Determination of acid insoluble ash in tea GB/T8308-2002 Standard download decompression password: www.bzxz.net

GB/T8308—2002
This standard is a revision of GB/T8308—1987 "Determination of insoluble ash content of tea acid". This standard is equivalent to ISO1577:1987 "Determination of insoluble ash content of tea acid". The main differences between this standard and ISO1577:1987 are: 1. No vegetable oil is added during the preparation of ash 2. When the solution changes from turbid to transparent during the determination, continue to heat for 5 minutes and then wash to neutral. The main difference between this standard and GB/T8308—1987 is: the sample weighing amount for total ash preparation is changed from 2g to 5g. This standard will replace GB/T8308--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: Guan Huixian and Sha Haitao. This standard is interpreted by the Hangzhou Tea Research Institute of the China National Federation of Supply and Marketing Cooperatives. 129
GB/T8308—-2002
ISO Foreword
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1 Scope
National Standard of the People's Republic of China
Tea-Determination of acid-insoluble ash content
Tea-Determination of acid-insoluble ash contentGB/T 8308—2002
eqyIS01577:1987
Replaces GB/T8308--1987
This standard specifies the principle, reagents and solutions, instrument group and application, determination steps and result calculation for the determination of acid-insoluble ash content in tea. This standard is applicable to the determination of acid-insoluble ash content in tea. 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 subtitles. GB/T8302--2002 Tea sampling
2 Preparation of ground tea sample and determination of dry matter content GB/T 8303---2002
GB/T 8306--2002
Determination of total ash in tea
3 Definitions
This standard adopts the following definitions.
Acid-insoluble ash Acid-insoluble ash The remaining part of the total ash after treatment with hydrochloric acid under specified conditions. 4 Principle
Treat the total carbon with hydrochloric acid solution, filter, burn and weigh the residue after burning. 5 Reagents and solutions
Hydrochloric acid (analytical grade) 10% solution: 24ml. Concentrated hydrochloric acid is diluted to 100mL with distilled water. 6 Instruments and appliances
Routine laboratory instruments and the following items:
6.1 Snail: porcelain, high type, capacity 50mL
6.2 Electric heating plate.
6.3 High temperature furnace: 525C±25C.
6.4 Water bath.
6.5 Desiccator: containing effective desiccant.
6.6 Folding balance: sensitivity 0.001g.
6.7 Ash-free filter paper.
6.8 Surface III: diameter 60mlc
Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on 2002-06-17 and implemented on 2002-12-01
6.9 Beaker: high type, capacity 100mL.
6.10 Ground crucible tongs.
7 Determination steps
7.1 Sampling
According to GB/T8302.
7.2 Sample preparation
According to GB/T8303.
7.3 Crucible preparation
GB/T 8308--2002
Place the clean crucible in a high-temperature furnace at 525℃±25℃ for 1h. When the furnace temperature drops to about 300℃, take out the crucible, cool it to room temperature in a desiccator, and weigh it (accurate to 0.001g). 7.4 Preparation of total ash
Weigh a uniformly ground sample 5 (accurate to 0.001g) and place it in the crucible. The other steps shall be in accordance with GB/T8306. Note: If the carbonization is not complete, a few drops of pure olive oil can be added to detect carbonization and ashification. 7.5 Determination
Wash the total ash content into a 100mL beaker with 25mL 10% hydrochloric acid solution, cover the surface, and carefully heat it in a water bath until the solution changes from turbid to transparent, and continue heating for 5 minutes. Filter it with ash-free filter paper while it is hot, and repeatedly wash the residue in the beaker and filter paper with hot distilled water in small amounts until the washing solution is no longer acidic (about 150mL). Move the filter paper and the residue into the original crucible, carefully evaporate the water in a water bath, move it into a high-temperature furnace, and burn it at 525℃±25C until there are no carbon particles (about 1h). When the furnace temperature drops to about 300, take it out, cool it to room temperature in a desiccator, and weigh it. Move it into a high-temperature furnace and burn it for 30 minutes, cool it and weigh it, and repeat this operation until the difference between two consecutive weighings does not exceed 0.001g, whichever is the smallest. 8 Calculation of results
8.1 Calculation method
The acid-insoluble ash in tea is expressed as dry mass fraction and calculated according to formula (1): Acid-insoluble ash (%) =
Wherein: M. mass of the acid-insoluble ash, g; M mass of the sample, g;
M mass of the sample, g,
m dry matter content of the sample, %. Www.bzxZ.net
If the requirements of repeatability (8.2) are met, take the arithmetic mean of the two measurements as the result (keep two decimal places). 8.2 Repeatability
The difference between the two measured values ​​of the same sample shall not exceed 0.02g per 100g sample. 132
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