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

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

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GB/T 6434-2022: Determination of crude fiber content in feeds

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%.
GB/T 6434-2022
GB
NATIONAL STANDARD OF THE
PEOPLE 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 potassium hydroxide solution (5.1.7), heat it, make it boil as soon as possible, and keep boiling for 30 min??1 min. After boiling begins, swirl the beaker every 5 min. Turn on the cooling device (5.2.5 and 5.2.10) during boiling to keep the volume of the boiling liquid constant.
5.4.1.8 Second filtration
The sample digestion solution is filtered through the filter crucible (5.2.2), and 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) is spread in the crucible, and a sieve plate (5.2.3) is covered on the filter aid 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. The filter residue is washed with hot water until it is neutral. Connect the filter crucible containing the filter residue of the sample to the cold extraction device (5.2.9), add 30 mL of acetone (5.1.3), soak for 5 min, and dry it by vacuum suction; repeat 3 times. 5.4.1.9 Drying
Place the filter crucible in the ashing dish (5.2.4), and dry at 130 ?????2 ??? for 2 h. Take it out, place it in a desiccator (5.2.6), cool to room temperature, and weigh quickly, accurate to 0.0001 g.
5.4.1.10 Ashing
Ash the filter crucible and ashing dish at 500 ??C??25 ??C for 30 min, take it out, and put the filter crucible and ashing dish in a desiccator (5.2.6) after preliminary cooling; cool wash the filter residue with hot water at least 3 times, each time with 30 mL of water, dry it by vacuum suction, and wash it until it is neutral. If the fat contained in the sample cannot be directly extracted with petroleum ether (5.1.2), proceed according to 5.4.2.6; otherwise, proceed according to 5.4.2.7.
NOTE 1: If the filtration blocks, blow air through carefully to remove the blockage. NOTE 2: The samples containing fat that cannot be directly extracted with petroleum ether refer to Type B samples that need to be hydrolyzed before fat extraction as specified in GB/T 6433. 5.4.2.6 Degreasing
Connect the filter crucible to the cold extraction device (5.2.9), wash the filter residue with acetone (5.1.3) three times, 30 mL each time, and dry it by vacuum suction; then, wash the filter residue with petroleum ether (5.1.2) for 3 times, each time 30 mL, and dry it by vacuum suction.
5.4.2.7 Alkaline digestion
Close the tap of the outlet, add 150 mL of boiling potassium hydroxide solution (5.1.7), add a few drops of defoamer (5.1.9), heat to make the solution boil as soon as possible, and keep boiling vigorously for 30 min??1 min.
5.4.2.8 Second filtration
Stop heating, open the tap of the discharge pipe, and drain the potassium hydroxide solution; wash with hot water at least 3 times, 30 mL each time, and dry it by vacuum suction; wash it until it is neutral. Connect the filter crucible to the cold extraction device (5.2.9), wash the filter residue 3 times with acetone (5.1.3), 30 mL each time, and dry it by vacuum suction.
NOTE: If it is difficult to filter, blow air through carefully to remove the blockage. 5.4.2.9 Drying
It is the same as 5.4.1.9.
5.4.2.10 Ashing
It is the same as 5.4.1.10.
5.4.2.11 Blank determination
Use the same quantity of filter aid (5.1.8), without the sample, to carry out a blank determination according to 5.4.2.4~5.4.2.10. The mass loss caused by ashing (5.4.2.10) shall not exceed 2 mg.
6.1.4 Hydrochloric acid solution ??? (0.5 mol/L): Measure 41.7 mL of hydrochloric acid, dilute it with water and make up to 1000 mL, and mix well.
6.1.5 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 according to GB/T 601. 6.1.6 Potassium hydroxide solution (0.23 mol/L??0.005 mol/L): Weigh 15.18 g of potassium hydroxide, dissolve it in water, dilute it to 1000 mL, and mix well. Calibrate it according to GB/T 601.
6.1.7 Filter paper.
6.2 Instruments and equipment
6.2.1 Analytical balance: The precision is 0.01 g and 0.0001 g.
6.2.2 Filter bag: The pore size is 20 ??m~25 ??m; it shall be heat stable, resistant to acid and alkaline digestion, or with equivalent performance.
6.2.3 Beaker.
6.2.4 Crucible.
6.2.5 Desiccator.
6.2.6 Drying oven: The temperature control accuracy is ??2 ??C.
6.2.7 Muffle furnace: The temperature control accuracy is ??25 ???.
6.2.8 Heating and cooling device: It shall be equipped with an independent heating unit and an appropriate cooling device to keep the volume of the liquid constant when boiling.
6.3 Samples
They are the same as 5.3.
6.4 Test procedure
6.4.1 Weighing
Carry out two experiments in parallel. Take the filter bag (6.2.2) that has been dried at 105 ??C??2 ??C for 2 h and cooled to room temperature in a desiccator, and weigh it to the nearest 0.0001 g. Weigh 1 g of the sample, accurate to 0.0001 g, put it into the filter bag, the volume of the sample is generally not more than 1/2 of the capacity of the filter bag, and seal it. If it is too full, the amount of sample can be appropriately reduced, but not less than 0.2 g. If the fat content of the sample exceeds 5% and the carbonate content exceeds 5%, start the processing from 6.4.2; if the fat content of the sample exceeds 5% and the carbonate content is less than 5%, proceed according to 6.4.2, and then continue the processing according to 6.4.4; if the fat content of the sample is less than 5% and the carbonate content exceeds 5%, start the processing from 6.4.3; if the fat content of the sample is less than 5% and the carbonate content is less than 5%, start the processing from 6.4.4.
6.4.2 Pre-degreasing
Put the filter bag containing the sample into a beaker (6.2.3), place it in a fume hood, add acetone (6.1.3) or petroleum ether (6.1.2) to completely submerge the sample; soak for 5 min, and during the period, use a glass rod to gently stir twice, or take out the filter bag and immerse it repeatedly twice; then, pour out the acetone or petroleum ether from the beaker. Repeat the operation 3 times. Take out the filter bag, put it on the filter paper (6.1.7), squeeze gently to remove the acetone or petroleum ether from the filter bag, and then let it volatilize in the fume hood for 30 min to remove the residual acetone or petroleum ether.
6.4.3 Removal of carbonates
Put the filter bag containing the sample in the beaker (6.2.3), add 100 mL of hydrochloric acid solution ??? (6.1.4), and soak for 5 min; take out the filter bag, wash it with water until it is neutral, and then gently squeeze out the water from the bag with filter paper (6.1.7).
6.4.4 Acid digestion
Put the filter bag containing the sample into the beaker (6.2.3), add the sulfuric acid solution (6.1.5) according to the ratio of the amount of 100 mL to 1 filter bag, heat to a slight boil, and keep for 30 min??1 min. Turn on the cooling device (6.2.8) during boiling to keep the volume of the boiling liquid constant. After boiling, take out the filter bag, wash it with hot water until it is neutral, and then gently squeeze out the water from the bag with filter paper (6.1.7).
6.4.5 Alkaline digestion
Put the acid-digested filter bag into a clean beaker (6.2.3), add the potassium hydroxide solution (6.1.6) according to the ratio of the amount of 100 mL to 1 filter bag, heat to a slight boil, and keep for 30 min??1 min. Turn on the cooling device (6.2.8) during boiling to keep the volume of the boiling liquid constant. After boiling, take out the filter bag, wash it with hot water until it is neutral, and then gently squeeze out the water from the bag with filter paper (6.1.7).
6.4.6 Degreasing
Put the alkaline-digested filter bag into a clean beaker, place it in a fume hood, and add m6 -- the mass of the filter bag and sample filter residue after drying, the unit is gram (g);
m8 -- the mass of crucible, filter bag, and sample filter residue after ashing, the unit is gram (g);
m7 -- the mass of the crucible, in grams (g);
m5 -- the mass of the filter bag after drying, in grams (g);
f -- the ashing correction factor for the blank filter bag, calculated according to formula (3);
m4 -- the mass of the sample, in grams (g);
mb6 -- the mass of the filter bag after drying in the blank test, in grams (g); mb8 -- the mass of the crucible and filter bag after ashing in the blank test, in grams (g);
mb7 -- the mass of the crucible in the blank test, in grams (g);
mb5 -- the mass of the filter bag in the blank test, in grams (g).
The determination result is expressed as the arithmetic mean of parallel determination results and is rounded to one decimal place.
6.6 Precision
The results of two independent determinations obtained under repeatability conditions shall meet the following requirements:
-- When the crude fiber content is < 5%, the absolute difference shall not be more than 0.6%;
-- When the crude fiber content is 5%~10%, the absolute difference shall not be more than 10% of the arithmetic mean;
-- When the crude fiber content is >10%, the absolute difference shall not be more than 6% of the arithmetic mean.

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