This standard specifies the method for preparing ground tea samples and determining their dry matter content. This standard is applicable to the analysis and determination of dry state results. GB/T 8303-2002 Preparation of ground tea samples and determination of their dry matter content GB/T8303-2002 standard download decompression password: www.bzxz.net

GB/T8303---2002
This standard is a revision of GB/T 8303--1987 "Preparation of ground tea samples and determination of dry matter content" while adopting IS01572:1980 "Tea-specific·Preparation of ground samples with known dry matter content" equivalently. The main difference between this standard and ISO1572:1980 is that the drying time is changed from 6h to 4h in the dry matter determination of the 103℃ constant weight method. The main differences between this standard and GB/T8303-1987 are: 1. The preparation of compressed tea ground samples is revised. 2. The pre-drying operation is deleted in the preparation of ground samples when the sample moisture is too high. 3. The second method for the determination of substance content is added: 120℃ drying method (quick method)". This standard will replace GB/T8303-1987 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. Drafting position of this standard: Hangzhou Tea Research Institute of the All-China Federation of Supply and Marketing Cooperatives. The main drafters of this standard are: Sun Anhua, Zhou Weilong, and Yang Shangxin. The Hangzhou Tea Research Institute of the All-China Federation of Supply and Marketing Cooperatives is responsible for the interpretation of this standard. 109
GB/T8303-
ISO Foreword
ISO (International Organization for Standardization) is an international federation of national standards organizations (ISO member bodies). Normally, the work of preparing international standards is undertaken by ISO technical committees. Each member body has the right to be represented on the committee if interested. Official or non-official international standards organizations affiliated with ISO also participate in the work. ISO cooperates closely with the International Electrotechnical Commission (IEC) on electrotechnical standards documents.
Draft international standards adopted by the technical committees are submitted to the member bodies for voting. Publication of international standards requires approval by not less than 75% of the member bodies.
International Standard ISO 1572 was prepared by Technical Committee IS0/TC32, Agricultural Products. 110
1 Scope
National Standard of the People's Republic of China
Preparation of ground sample and determinationof dry matter
Tea \ - Preparation of ground sample and determinationof dry matter content
This standard specifies the methods for preparing ground tea samples and determining their dry matter content. This standard is applicable to analytical determinations in which the results are expressed in dry form. 2 Referenced standards
GB/T 8303—2002
eqv ISO 1572:1980
Replaces GB/T8303---1987
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T8302-2002 Tea sampling
GB/T8304—2002 Tea moisture determination
3 Definitions
This standard adopts the following definitions.
fMaterialdry matter
Grind the sample and heat it to constant weight at a specified temperature, and the remaining material. 4 Principle
Grind the sample and heat it in an electric constant temperature drying oven at a specified temperature to remove moisture to constant weight, and weigh it. 5 Instruments and appliances
Conventional laboratory instruments and the following items:
5.1 Crusher: Made of materials that do not absorb moisture; dead corners as small as possible, easy to clean; so that the ground sample can completely pass through the sieve with an aperture of 600 μm~1 000 μm.
5.2 Sample container: Brown glass sample bottle or metal sample box can be used. It should be clean, dry and airtight; made of materials that do not react with the sample; the size should be large enough to fill the ground sample.
5.3 Aluminum drying oven: Its cover, inner diameter 75mm~80mm. 5.4 Blower electric constant temperature drying oven: can automatically control the temperature of ±2°C. 5.5t Desiccant: Contains effective desiccant.
5.6 Analytical balance: sensitivity 0.001g.
Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on 2002-06-17, implemented on 2002-12-01
Preparation of ground samples
6.1 Sampling
Sampling shall be carried out in accordance with the provisions of GB/T8302.
6.2 Preparation of samples
GB/T8303-
All kinds of tea other than compressed tea: First grind a small amount of sample with a grinder (5.1), discard it, and then grind the rest as the sample to be tested in 6.2.1
.
Compressed tea: Divide the compressed tea into 4 to 8 portions with a hammer and chisel, then take samples from different places in each portion, crush them with a hammer, mix them, and prepare samples in accordance with the provisions of 6.2.2
6.2.1.
Dry matter determination
7.1 Preparation of aluminum baking dish
Perform according to 6.3 of GB/T8304--2002. 7.2 Determination steps
7.2.1 Method 1: 103°C constant weight method (arbitration method) Determine according to 6.4.1 of GB/T8304-2002. 7.2.2 Method 2: 120°C drying method (quick method) Determine according to 6.4.2 of GB/T8304-2002. 8 Result calculation
8.1 Calculation method
The dry matter content of the ground sample is expressed as mass fraction and is calculated according to formula (1): Dry matter content (%) =
Where: M. —Original mass of the sample, g; M.
Mass of the dried sample, g.
× 100
If the repeatability requirement (8.2) is met, the arithmetic mean of the two determinations shall be taken as the result (keep one decimal place). 8.2 RepeatabilityWww.bzxZ.net
The difference between the two determinations of the same sample shall not exceed 0.2g per 100g of sample. Note: When the second method is used to determine the dry matter of tea, if the repeatability requirement is not met, the first method shall be used for determination. 112
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