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GB/T 6432-2018 PDF English

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GB/T 6432-2018: Determination of crude protein in feeds -- Kjeldahl method
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GB/T 6432: Evolution and historical versions

Standard IDContents [version]USDSTEP2[PDF] deliveryName of Chinese StandardStatus
GB/T 6432-2018English105 Add to Cart 0-9 seconds. Auto-delivery Determination of crude protein in feeds -- Kjeldahl method Valid
GB/T 6432-1994English199 Add to Cart 2 days Method for the determination of crude protein in feedstuffs Obsolete
GB 6432-1986English199 Add to Cart 2 days Method for the determination of crude protein in feedstuffs Obsolete

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GB/T 6432-2018: Determination of crude protein in feeds -- Kjeldahl method

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GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA ICS 65.120 B 46 Replacing GB/T 6432-1994 Determination of crude protein in feeds - Kjeldahl method Issued on. SEPTEMBER 17, 2018 Implemented on. APRIL 01, 2019 Issued by. State Administration for Market Regulation; Standardization Administration of the People’s Republic of China.

Table of Contents

Foreword... 3 1 Scope... 4 2 Normative references... 4 3 Principle... 4 4 Reagents or materials... 4 5 Instruments and equipment... 5 6 Sample... 6 7 Test steps... 6 8 Test data processing... 8 9 Precision... 9

Foreword

This Standard was drafted in accordance with the rules given in GB/T 1.1-2009. This Standard replaces GB/T 6432-1994 Method for the determination of crude protein in feedstuffs. Compared with GB/T 6432-1994, the main technical changes, except editorial changes, are as follows. -- Modify the standard name (see cover); -- Modify the scope of application (see Chapter 1); -- Add provisions on significant figures of calculation results (see Chapter 8). This Standard shall be under the jurisdiction of National Technical Committee 76 on Feed Industry of Standardization Administration of China (SAC/TC 76). Drafting organizations of this Standard. Institute of Quality Standard and Testing Technology for Agro-Products of CAAS [China National Feed Quality Control Center (Beijing)] Chief drafting staffs of this Standard. Xiao Zhiming, Fan Xia, Ma Dongxia, Li Libei, Wang Shi, Jia Zheng, Liu Xiaolu, Wang Zhigang, Liu Jun. The previous versions of the standard which are replaced by this Standard are. -- GB 6432-1986, GB/T 6432-1994. Determination of crude protein in feeds - Kjeldahl method

1 Scope

This Standard specifies the Kjeldahl method for the determination of crude protein in feeds. This Standard applies to the determination of crude protein in feed raw materials, compound feeds, concentrated feeds, concentrate supplements and additive premixed feeds.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies to this document. For undated references, the latest edition (including any amendment) applies to this document. GB/T 601, Chemical reagent - Preparations of reference titration solutions GB/T 6682, Water for analytical laboratory use - Specification and test methods GB/T 14699.1, Feeding stuffs - Sampling GB/T 20195, Animal feeding stuffs - Preparation of test samples

3 Principle

The sample is digested by sulfuric acid under the action of the catalyst, and the nitrogen- containing compound is converted into ammonium sulfate. Add alkali to distill to make ammonia escape;

4 Reagents or materials

Unless otherwise stated, only use analytical reagents. 4.1 Water. GB/T 6682, grade 3. 4.2 Boric acid. chemical pure. 4.3 Sodium hydroxide. chemical pure. 4.4 Sulfuric acid. chemical pure. 4.5 Ammonium sulfate. 4.11 Hydrochloric acid standard titration solution. c(HCl) = 0.1 mol/L or 0.02 mol/L, prepared and calibrated according to GB/T 601. 4.12 Methyl red ethanol solution. Weigh 0.1 g of methyl red; use ethanol to dissolve and dilute to 100 mL. 4.13 Bromocresol green ethanol solution. Weigh 0.5 g of bromocresol green; use ethanol to dissolve and dilute to 100 mL.

5 Instruments and equipment

5.1 Analytical balance. sensitivity 0.000 1g. 5.2 Boiling sterilizer or electric furnace. 5.3 Kjeldahl flask. 250 mL. 5.4 Boiling and sterilization tube. 250 mL.

6 Sample

Take representative feed samples according to GB/T 14699.1; use the quartering method to reduce the sampling.

7 Test steps

7.1 Semi-micro method (arbitration method) 7.1.1 Sample boiling and sterilization 7.1.1.1 Kjeldahl flask boiling and sterilization Perform two tests in parallel. Weigh 0.5 g ~ 2 g of the sample (nitrogen content 5 mg ~ 80 mg, accurate to 0.000 1 g); 7.1.2 Distillation of ammonia After the boiled-and-sterilized solution of the sample is cooled, add 20 mL of water; transfer it to a 100 mL volumetric flask; after cooling, use water to dilute to the mark; shake well; use it as the sample decomposition solution. Immerse the end of the condenser tube of the semi-micro distillation device into the Erlenmeyer flask filled with 20 mL of boric acid absorption solution I (4.8) and 2 drops of mixed indicator (4.14). 7.1.3 Titration Immediately use 0.1 mol/L or 0.02 mol/L of hydrochloric acid standard titration solution (4.11) to titrate the absorption solution after distillation in 7.1.2.The solution changes from blue-green to gray-red as the titration end point. 7.2 Full volume method 7.2.1 Sample boiling and sterilization Follow the steps in 7.1.1. 7.2.2 Distillation of ammonia 7.2.2.3 When using an automatic Kjeldahl nitrogen analyzer, carry out the measurement according to the instrument operation manual. 7.2.3 Titration Use 0.1 mol/L hydrochloric acid standard titration solution (4.11) to titrate the absorption solution. The solution changes from blue-green to gray-red as the end point. 7.3 Distillation step verification Accurately weigh 0.2 g of ammonium sulfate (accurate to 0.000 1 g), to replace the sample; operate according to the steps in 7.1 or 7.2.The measured nitrogen content of ammonium sulfate shall be (21.19±0.2) %. Otherwise, check whether the steps of the addition of alkali, distillation and titration are correct. 7.4 Blank determination Accurately weigh 0.5 g of sucrose (accurate to 0.000 1 g), to replace the sample; carry out blank determination according to 7.1 or 7.2.

8 Test data processing

The crude protein content in the sample is expressed in mass fraction w, and the value is expressed in mass fraction (%), and calculated according to Formula (1).

9 Precision

Under repeatability conditions, the ratio of the absolute difference between two independent measurement results and their arithmetic mean TO the mean shall meet the following requirements. ......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.


      

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