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GB/T 6438-2025Determination of crude ash in feeds (English PDF)

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Issued by

State Administration for Market Regulation

Level / Type

National · Recommended

Issue date

August 1, 2025

Implementation date

February 1, 2026

Scope

GB/T 6438-2025 (Determination of crude ash in feeds) is available as an English-translated PDF.

GB/T 6438-2025 — This document describes a method for the determination of crude ash in feeds. This document applies to the determination of crude ash in compound feeds, concentrate feeds, concentrate supplements, additive premixes, and feed ingredients.

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Document preview — GB/T 6438-2025

National Standard of the People's Republic of China

ICS: 65.120

Issued by: State Administration for Market Regulation

Foreword...3
1 Scope...6
2 Normative references...6
3 Terms and definitions...6
4 Principle...6
5 Reagents or materials...6
6 Apparatus...7
7 Samples...7
8 Test procedure...7
9 Test data processing...8
10 Precision...9
Bibliography...10

Foreword

This document was drafted in accordance with the provisions of GB/T 1.1-2020

"Directives for standardization - Part 1.Rules for the structure and drafting of

standardizing documents".

This document replaces GB/T 6438-2007, "Determination of crude ash in feeds."

Compared with GB/T 6438-2007, in addition to structural adjustments and editorial

changes, the main technical changes are as follows.

a) MODIFY the scope of application (see Clause 1 of this document; Clause 1 of the

2007 edition);

b) MODIFY the principle (see Clause 4 of this document; Clause 4 of the 2007

edition);

c) ADD the "Reagents or materials" (see Clause 5 of this document);

d) DELETE the "Sampling" (see Clause 6 of the 2007 edition);

e) MODIFY the technical requirements for box-type resistance furnace and

incineration dish (see 6.2 and 6.5 of this document; 5.2 and 5.5 of the 2007

edition);

f) MODIFY the "Sample preparation" to "Samples" (see Clause 7 of this document;

7.1 of the 2007 edition);

g) MODIFY the sample mass (see 8.1 of this document; 7.2 of the 2007 edition);

h) MODIFY the "Determination" to "Carbonization and incineration" (see 8.2 of

this document; 7.3 of the 2007 edition);

i) MODIFY the requirements for precision (see Clause 10 of this document; 9.2 of

the 2007 edition);

j) DELETE the "Interlaboratory test," "Reproducibility," and "Test report" (see 9.1,

9.3, and Clause 10 of the 2007 edition).

This document has modified and adopted ISO 5984.2022, "Animal feeding stuffs -

Determination of crude ash."

Compared with ISO 5984.2022, this document has made the following structural

adjustments.

- ADD "Reagents or materials" as Clause 5;

- Clause 6 corresponds to Clause 5 of ISO 5984.2022;

Determination of crude ash in feeds

1 Scope

This document describes a method for the determination of crude ash in feeds.

This document applies to the determination of crude ash in compound feeds,

concentrate feeds, concentrate supplements, additive premixes, and feed ingredients.

2 Normative references

The following referenced documents are indispensable for the application of this

document. For dated references, only the edition cited applies. For undated references,

the latest edition of the referenced document (including any amendments) applies.

GB/T 6682 Water for analytical laboratory use - Specification and test methods

(GB/T 6682-2008, ISO 3696.1987, MOD)

GB/T 20195 Animal feed - Preparation of test samples (GB/T 20195-2024, ISO

6498.2012, MOD)

3 Terms and definitions

For the purpose of this document, the following terms and definitions apply.

3.1

crude ash

Residue obtained after incineration at 550 °C ± 25 °C under the conditions specified in

this document.

NOTE. Crude ash is usually expressed as a percentage by mass.

4 Principle

A test specimen is carbonized and then incinerated at 550 °C ± 25 °C; after cooling,

weigh the mass of the ash and calculate its percentage of the sample mass.

5 Reagents or materials

Unless otherwise specified, only analytically pure reagents shall be used.

5.1 Water. GB/T 6682, Grade 3.

5.2 Hydrochloric acid solution (3 mol/L). Measure 250 mL of hydrochloric acid, dilute

to 1000 mL with water, and mix thoroughly.

6 Apparatus

6.1 Analytical balance. accuracy of 0.001 g.

6.2 Box-type resistance furnace. electrically heated, with temperature control and

display functions, or capable of programmable temperature control; the temperature at

the sample location can be maintained at a stable 550 °C ± 25 °C.

6.3 Electric constant temperature drying oven. capable of being controlled at 103 °C ±

2 °C.

6.4 Electric hot plate or electric furnace.

6.5 Incineration dish. porcelain crucible, quartz crucible, platinum crucible, or platinum

alloy (e.g., 10 % Pt, 90 % Au) crucible, volume 30 mL ~ 50 mL. For samples with a

low specific gravity that are inclined to swell on carbonization (e.g., whey powder), it

should use crucibles with a larger bottom area.

NOTE. Before use, new porcelain or quartz crucibles shall be boiled in hydrochloric acid solution

(5.2), cleaned with water (5.1), and then dried.

6.6 Desiccator. with an effective desiccant, such as color-changing silica gel.

7 Samples

Prepare according to GB/T 20195.For solid samples, take at least 200 g, crush so that

it passes through a 1.0 mm test sieve, mix thoroughly, and store in a sealed container

until ready for use. For uniformly distributed liquid and semi-solid samples, take at least

200 g, directly store in a sealed container until ready for use; for non-uniformly

distributed liquid and paste samples, homogenize before testing.

8 Test procedure

8.1 Sample weighing

Perform two parallel tests. Place the incineration dish (6.5) in a box-type resistance

furnace (6.2) at 550 °C ± 25 °C for at least 30 min, transfer to a desiccator (6.6) and

cool to room temperature, and weigh to the nearest 0.001 g. Weigh 2 g (to the nearest

0.001 g) of specimen (weigh approximately 1 g for samples that are inclined to swell

on carbonization) and place it in the incineration dish (6.5).

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This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 10 pages — is available in the English PDF.

Referenced standards

Normative references

ISO 3696.1987

Cited by

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