GB/T 8303-2013Tea -- Preparation of ground sample and determination of dry matter content (English PDF)

Foreword

This standard was drafted in accordance with GB/T 1.1-2009 given rules.

This standard replaces GB/T 8303-2002 "ground tea preparation and determination of dry matter content in the sample." This standard and GB/T 8303-Compared to 2002, the main technical changes are as follows.

--- Modify the requirements of the sample container, brown glass vials can be used to delete or metal-like cartridge;

--- Increased quality glass baking dish;

--- Modify the repeatability requirement. the difference between the results of two measurements per 100g sample shall not exceed 0.2g, modified to duplicate conditions the absolute difference between the measurement results of the same sample must not exceed 5% of the arithmetic mean.

This standard uses redrafted law revision adopted ISO 1572. 1980 "Tea milled sample preparation and determination of dry matter content." this standard and ISO 1572. 1980 as compared to the main technical differences are as follows.

--- Pulverized sample through a pore size of 500µm sieve modified to grind the sample through a pore size of 600µm ~ 1000µm sieve;

--- Remove the pre-drying process;

--- Increasing the preparation of pressed tea;

--- Measured in the sample drying time constant weight in water method 103 °C ± 2 °C modified to 4h from 6h;

--- Repeatability. the difference between the results of two measurements per 100g sample shall not exceed 0.3g, modify the conditions of the same sample in duplicate eligible Measurement results obtained absolute difference should not exceed 5% of the arithmetic mean;

--- Increased 120 °C drying method (rapid method) as the second law of this standard.

This standard also made the following structural modifications.

--- The International Standard Preparation of samples and sampling Chapter 6 Chapter 7 grated modify this standard 6.1 6.2 Sampling and sample preparation.

This standard also made the following editorial changes.

--- Remove the ISO 1573. 1980 Foreword.

The standard proposed by China Federation of Supply and Marketing Cooperatives.

This standard by the National Standardization Technical Committee of tea (SAC/TC339) centralized.

This standard was drafted. China Federation of Supply and Marketing Cooperatives Hangzhou Tea Research Institute, the National Tea Quality Supervision and Inspection Center.

1 Scope

This standard specifies the sample preparation and tea ground dry matter content measured approach.

This standard applies to the dry state shows the results of the analysis.

2 Normative references

The following documents for the application of this document is essential. For dated references, only the dated version suitable for use herein Member. For undated references, the latest edition (including any amendments) applies to this document.

GB/T 8302 sampling Tea (GB/T 8302-2013, ISO 1839. 1980, NEQ) GB/T 8304 Determination of tea division (GB/T 8304-2013, ISO 1573. 1980, MOD)

3 Terms and Definitions

The following terms and definitions apply to this document.

Dry drymatter

Pulverized sample at a predetermined temperature, heating to constant weight of the remaining material.

Principle 4

Ground samples and at a predetermined temperature, with electric oven heated to remove moisture to constant weight and weighed.

5 Apparatus and appliances

5.1 mill. the material does not absorb moisture made; dead as small as possible, easy to clean; keep the ground sample completely through a pore size of 600µm ~ 1000µm sieve.

5.2 Sample container. should be clean, dry, dark, airtight glass or other material does not react with the sample made; sized to fill grind Sample is appropriate.

5.3 Quality aluminum or glass baking dish. a cover, an inner diameter of 75mm ~ 80mm.

5.4 blast electric oven. 103 °C ± 2 °C.

5.5 dryer. built effective desiccant.

5.6 Analysis of balance. a sense of the amount of 0.001g.

6 Grinding sample preparation