GB/T 6434-2022 English PDF (GBT6434-2022)

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GB/T 6434-2022: Determination of crude fiber content in feeds
GB/T 6434-2022
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 65.120
CCS B 46
Replacing GB/T 6434-2006
Determination of crude fiber content in feeds
(ISO 6865:2000, Animal feeding stuffs - Determination of crude fiber content -
Method with intermediate filtration, MOD)
ISSUED ON: DECEMBER 30, 2022
IMPLEMENTED ON: JULY 1, 2023
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 6
2 Normative references ... 6
3 Terms and definitions ... 6
4 Principles ... 7
5 Filter crucible method (arbitration method) ... 7
6 Filter bag method ... 13
References ... 18
Determination of crude fiber content in feeds
1 Scope
This document describes the filter crucible and filter bag methods for the determination
of crude fiber content in feeds.
This document is applicable to the determination of crude fiber content in compound
feeds, concentrated feeds, concentrate supplements, additive premix feeds, and feed
raw materials.
The limit of quantitation for crude fiber in this document is 1.0%.
2 Normative references
The following documents contain the provisions which, through normative reference in
this document, constitute the essential provisions of this document. For the dated
referenced documents, only the versions with the indicated dates are applicable to this
document; for the undated referenced documents, only the latest version (including all
the amendments) is applicable 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 6682-2008, ISO 3696:1987, MOD)
GB/T 20195 Animal feeding stuffs - Preparation of test samples (GB/T 20195-2006,
ISO 6498:2012, MOD)
3 Terms and definitions
The following terms and definitions apply to this document.
3.1 crude fiber content
According to the conditions specified in this document, the percentage of the mass lost
by ashing of the dry filter residue obtained after the sample is digested with acid and
alkali respectively to the mass of the sample.
4 Principles
The sample is treated with boiling dilute sulfuric acid, filtered to separate the filter
residue, and washed; it is treated with boiling potassium hydroxide solution, filtered to
separate the filter residue, washed, degreased, dried, weighed, and then ashed. The
percentage of mass lost by ashing to the sample mass is the crude fiber content in the
sample.
5 Filter crucible method (arbitration method)
5.1 Reagents or materials
Unless otherwise specified, only analytical reagents are used.
5.1.1 Water: Grade III specified in GB/T 6682.
5.1.2 Petroleum ether: The boiling range is 30 °C~60 °C.
5.1.3 Acetone.
5.1.4 Hydrochloric acid solution I (0.5 mol/L): Measure 41.7 mL of hydrochloric acid,
dilute it with water and make up to 1000 mL, and mix well.
5.1.5 Hydrochloric acid solution II (4 mol/L): Measure 333 mL of hydrochloric acid,
dilute it with water and make up to 1000 mL, and mix well.
5.1.6 Sulfuric acid solution (0.13 mol/L±0.005 mol/L): Measure 7.2 mL of sulfuric acid,
slowly inject it into 1000 mL of water, mix well, and calibrate the solution according to
GB/T 601.
5.1.7 Potassium hydroxide solution (0.23 mol/L±0.005 mol/L): Weigh 15.18 g of
potassium hydroxide, dissolve in water, dilute to 1000 mL, and mix well; calibrate the
solution according to GB/T 601.
5.1.8 Filter aid: Sea sand, diatomaceous earth, or other materials with equivalent
performance. Before use, sea sand is submerged in hydrochloric acid solution II (5.1.5),
boiled, and washed with water until it is neutral; then, it is burned at 500 °C±25 °C for
2 h, taken out, cooled, and placed in a desiccator for later use.
5.1.9 Defoamer: n-octanol or silicone oil.
5.2 Instruments and equipment
5.2.1 Balance: The precision is 0.01 g and 0.0001 g.
The sample is prepared according to GB/T 20195, at least 200 g, and crushed so that it
all passes through an analytical sieve with a pore size of 1 mm; then, it is mixed well
and put into a closed container for later use.
5.4 Test procedure
5.4.1 Manual operation method by using a filter crucible
5.4.1.1 Weighing
Carry out two experiments in parallel. Weigh about 1 g of the sample (accurate to
0.0001 g). If the fat content of the sample exceeds 10% and the carbonate content
exceeds 5%, put it in the filter crucible (5.2.2) and start the processing from 5.4.1.2; if
the fat content of the sample is more than 10% and the carbonate content is less than
5%, put it in the filter crucible (5.2.2), proceed according to 5.4.1.2, and then continue
the processing according to 5.4.1.4; If the fat content of the sample is less than 10% and
the carbonate content is more than 5%, put it in the beaker (5.2.5), start the processing
from 5.4.1.3; if the fat content of the sample is less than 10% and the carbonate content
is less than 5%, put it in the beaker (5.2.5) and start the processing from 5.4.1.4.
NOTE: The content of carbonate is calculated as calcium carbonate.
5.4.1.2 Pre-degreasing
Connect the filter crucible containing the sample to the cold extraction device (5.2.9),
add 30 mL of petroleum ether (5.1.2), soak for 5 min, and dry it by vacuum suction;
repeat 3 times, and then transfer all the filter residue to the beaker (5.2.5).
5.4.1.3 Removal of carbonates
Add 100 mL of hydrochloric acid solution I (5.1.4), stir continuously for 5 min, and
carefully transfer the mixture to the filter crucible (5.2.2), whose bottom is in advance
covered with a thin layer of filter aid (5.1.8, the thickness of the filter aid is about 1/5
of the height of the filter crucible); then, dry it by vacuum suction. Wash the beaker
with 100 mL of water, transfer the washing liquid to the filter crucible (5.2.2), dry it by
suction, and repeat washing with water once. Transfer all the sample and filter aid to
the original beaker.
5.4.1.4 Acid digestion
Add 150 mL of sulfuric acid solution (5.1.6), heat to make it boil as soon as possible,
and keep boiling for 30 min±1 min. After boiling begins, swirl the beaker every 5 min.
If necessary, add a few drops of defoamer (5.1.9). Turn on the cooling device (5.2.5 and
5.2.10) during boiling to keep the volume of the boiling liquid constant.
5.4.1.5 First filtration
Spread a layer of filter aid (5.1.8, the thickness of the filter aid is about 1/5 of the height
of the filter crucible) in the filter crucible (5.2.2), and cover the filter aid with a sieve
plate (5.2.3) to prevent splashing. After the digestion is completed, transfer the
digestion liquid to a filter crucible, filter the liquid in a vacuum, and dry it as much as
possible. Wash the filter residue 5 times with hot water, about 10 mL each time, and dry
it by vacuum suction. After stopping suction, add 30 mL of acetone (5.1.3) to cover the
filter residue, let it stand for 5 min, and dry it by suction.
NOTE: Make sure that the filter plate is always covered with filter aid so that crude fibers do not directly
contact the filter plate.
5.4.1.6 Degreasing
Connect the filter crucible containing the filter residue of the sample to the cold
extraction device (5.2.9), add 30 mL of petroleum ether (5.1.2), soak for 5 min, and dry
it by vacuum suction; repeat 3 times.
5.4.1.7 Alkaline digestion
Transfer all the filter residue to the same beaker used for acid digestion, add 150 mL of...