prEN ISO 16634-1

Food products - Determination of the total nitrogen content by combustion according to the Dumas principle and calculation of the crude protein content - Part 1: Oilseeds and animal feeding stuffs (ISO/DIS 16634-1:2025)

ISO 16634-1:2008 specifies a method for the determination of the total nitrogen content and the calculation of crude protein content of oilseeds and animal feeding stuffs.
This method, like the Kjeldahl method, does not distinguish between protein nitrogen and non-protein nitrogen. For the calculation of protein content, various conversion factors are used.
This method is not applicable to milk and milk products.

Lebensmittelerzeugnisse - Bestimmung des Gehaltes an Gesamtstickstoff mit dem Verbrennungsverfahren nach Dumas und Berechnung des Gehaltes an Rohprotein - Teil 1: Ölsaatenschrote und Futtermittel (ISO/DIS 16634-1:2025)

Produits alimentaires - Détermination de la teneur en azote total par combustion selon le principe Dumas et calcul de la teneur en protéines brutes - Partie 1: Graines oléagineuses et aliments des animaux (ISO/DIS 16634-1:2025)

L'ISO 16634-1:2008 spécifie une méthode pour la détermination de la teneur en azote total et le calcul de la teneur en protéines brutes des graines oléagineuses et des aliments pour animaux.
Cette méthode, comme la méthode Kjeldahl, ne distingue pas l'azote protéique de l'azote non protéique. Divers facteurs de conversion sont utilisés pour le calcul de la teneur en protéines.
Cette méthode ne s'applique pas au lait et aux produits laitier.

Živila - Določevanje skupnega dušika s sežigom po Dumasu in izračunom deleža surovih beljakovin - 1. del: Oljna semena in krma (ISO/DIS 16634-1:2025)

General Information

• Status: Not Published
• Publication Date: 04-Apr-2027
• ICS: 65.120 - Animal feeding stuffs
• ICS: 67.060 - Cereals, pulses and derived products
• ICS: 67.200.20 - Oilseeds
• Technical Committee: CEN/TC 327 - Animal feeding stuffs - Methods of sampling and analysis
• Drafting Committee: CEN/TC 327 - Animal feeding stuffs - Methods of sampling and analysis
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 04-Dec-2025
• Completion Date: 04-Dec-2025
• Ref Project: oSIST prEN ISO 16634-1:2025 - Food products - Determination of the total nitrogen content by combustion according to the Dumas principle and calculation of the crude protein content - Part 1: Oilseeds and animal feeding stuffs (ISO/DIS 16634-1:2025)

Relations

• Revises: EN ISO 16634-1:2008 - Food products - Determination of the total nitrogen content by combustion according to the Dumas principle and calculation of the crude protein content - Part 1: Oilseeds and animal feeding stuffs (ISO 16634-1:2008)
• Effective Date: 28-Aug-2024

Overview

The prEN ISO 16634-1 standard, titled Food products - Determination of the total nitrogen content by combustion according to the Dumas principle and calculation of the crude protein content - Part 1: Oilseeds and animal feeding stuffs (ISO/DIS 16634-1:2025), is an updated international standard developed by CEN and ISO. It specifies a precise and reliable method for measuring the total nitrogen content in oilseeds and animal feeding stuffs using combustion analysis following the Dumas principle. Subsequently, it details how to calculate the crude protein content based on nitrogen results by applying standard conversion factors.

This method is recognized as a faster, safer, and environmentally friendlier alternative to the traditional Kjeldahl method, widely used in laboratories for protein analysis. It is important to note that the method does not differentiate between protein and non-protein nitrogen, and it is not applicable to milk or milk products.

Key Topics

• Scope of Application

  • Oilseeds and oilseed meals
  • Compound feed and feed raw materials (plant origin)
  • Premixtures and excreta (accuracy to be checked for excreta)
  • Not suitable for milk and dairy products

• Analytical Principle

  • Combustion of samples at ≥850°C in the presence of pure oxygen
  • Conversion of nitrogen in the sample to nitrogen gas measured quantitatively
  • Resulting total nitrogen content used to estimate crude protein by multiplication with factor 6.25

• Comparison with Kjeldahl Method

  • Both measure total nitrogen, but Dumas is faster and does not use hazardous chemicals
  • Dumas measures total nitrogen including all non-protein nitrogen, often giving slightly higher results
  • Kjeldahl measures only part of the non-protein nitrogen content

• Standard Compliance and Accuracy

  • Sampling and sample preparation according to referenced ISO standards (e.g., ISO 664, ISO 665)
  • Calibration and oxygen demand control are crucial for precision
  • Interlaboratory reproducibility and repeatability are validated

Applications

• Quality Control in Agriculture and Feed Production
  Monitoring crude protein content in oilseeds and animal feeds ensures compliance with nutritional standards and helps optimize feed formulation for livestock health and productivity.

• Regulatory and Trade Compliance
  Accurate protein content determination supports regulatory certification and trade documentation for seed and feed exports/imports.

• Research and Development
  Food and feed manufacturers utilize ISO 16634-1 method results to improve product formulations and verify ingredient quality.

• Environmental and Waste Monitoring
  The method applies to excreta analysis, aiding in studies involving nutrient cycling and environmental impact assessment.

Related Standards

This standard complements and integrates with other important ISO standards related to oilseed and feed quality analysis:

• ISO 664 - Reduction of oilseed laboratory samples to test samples
• ISO 665 - Determination of moisture and volatile matter content in oilseeds
• ISO 771 - Moisture content determination in oilseed meals
• ISO 6496 - Moisture and volatile matter content in animal feeding stuffs
• ISO 6498 - Guidelines for sample preparation of animal feeding stuffs
• ISO 12099 - Application of near infrared spectrometry for animal feeding stuffs, cereals, and milled products
• ISO 16634-2 - Determination of nitrogen and crude protein in cereals, pulses, and milled cereal products

By following the methodologies established in prEN ISO 16634-1, laboratories and industries benefit from standardized, reproducible, and internationally accepted protein content determination, enhancing food safety and quality management worldwide.

---

Keywords: Dumas method, crude protein content, total nitrogen determination, oilseeds, animal feeding stuffs, combustion analysis, ISO 16634-1, nitrogen content measurement, feed quality, protein analysis standard, CEN standard.

Standards Content (Sample)

SLOVENSKI STANDARD
01-november-2025
Živila - Določevanje skupnega dušika s sežigom po Dumasu in izračunom deleža
surovih beljakovin - 1. del: Oljna semena in krma (ISO/DIS 16634-1:2025)
Food products - Determination of the total nitrogen content by combustion according to
the Dumas principle and calculation of the crude protein content - Part 1: Oilseeds and
animal feeding stuffs (ISO/DIS 16634-1:2025)
Lebensmittelerzeugnisse - Bestimmung des Gehaltes an Gesamtstickstoff mit dem
Verbrennungsverfahren nach Dumas und Berechnung des Gehaltes an Rohprotein - Teil
1: Ölsaatenschrote und Futtermittel (ISO/DIS 16634-1:2025)
Produits alimentaires - Détermination de la teneur en azote total par combustion selon le
principe Dumas et calcul de la teneur en protéines brutes - Partie 1: Graines
oléagineuses et aliments des animaux (ISO/DIS 16634-1:2025)
Ta slovenski standard je istoveten z: prEN ISO 16634-1
ICS:
65.120 Krmila Animal feeding stuffs
67.200.20 Oljnice Oilseeds
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 16634-1
ISO/TC 34
Food products - Determination
Secretariat: AFNOR
of the total nitrogen content by
Voting begins on:
combustion according to the Dumas
2025-09-11
principle and calculation of the
Voting terminates on:
crude protein content —
2025-12-04
Part 1:
Oilseeds and animal feeding stuffs
Produits alimentaires - Détermination de la teneur en azote total
par combustion selon le principe Dumas et calcul de la teneur en
protéines brutes —
Partie 1: Graines oléagineuses et aliments des animaux
ICS: 65.120; 67.200.20
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document has not been edited by the ISO Central Secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 16634-1:2025(en)
DRAFT
ISO/DIS 16634-1:2025(en)
International
Standard
ISO/DIS 16634-1
ISO/TC 34
Food products - Determination
Secretariat: AFNOR
of the total nitrogen content by
Voting begins on:
combustion according to the Dumas
principle and calculation of the
Voting terminates on:
crude protein content —
Part 1:
Oilseeds and animal feeding stuffs
Produits alimentaires - Détermination de la teneur en azote total
par combustion selon le principe Dumas et calcul de la teneur en
protéines brutes —
Partie 1: Graines oléagineuses et aliments des animaux
ICS: 65.120; 67.200.20
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document has not been edited by the ISO Central Secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 16634-1:2025(en)
ii
ISO/DIS 16634-1:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents . 2
6 Apparatus . 3
7 Sampling . 4
8 Preparation of test sample . 4
9 Procedure . 5
9.1 General .5
9.2 Test portion .5
9.3 Control of oxygen demand .5
9.4 Calibration .5
9.5 Determination .5
9.6 Detection and integration .6
10 Calculation and expression of results . 6
10.1 Calculation .6
10.1.1 Nitrogen content .6
10.1.2 Crude protein content .6
10.2 Expression of results . .7
11 Precision . 7
11.1 Interlaboratory tests .7
11.2 Repeatability .7
11.3 Reproducibility .7
12 Test report . 8
Annex A (informative) Flowchart for the basic design of a Dumas apparatus . 9
Annex B (informative) Equipment calibration . 10
Annex C (informative) Result of collaborative studies .12
Bibliography .21

iii
ISO/DIS 16634-1:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO [had/had not] received notice of
(a) patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 10, Animal
feeding stuffs.
This second/third/… edition cancels and replaces the first/second/… edition (ISO #####:####), which has
been technically revised.
The main changes are as follows:
— Removal of informative annex B (Schemes of suitable types of Dumas apparatus), annex D (Examples of
factors for converting nitrogen content to protein content) and annex F (Relationship between Dumas
nitrogen and Kjeldahl nitrogen).
— Harmonization with ISO 16634-2.
A list of all parts in the ISO 16634 series can be found on the ISO website.
— Part 1 : Oilseeds and animal feeding stuffs
— Part 2 : Cereals, pulses and milled cereal products
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/DIS 16634-1:2025(en)
Introduction
For a long time the Kjeldahl method has been the most frequently used method for the determination of
protein content of food products. However, in recent years, the Kjeldahl method has increasingly been
replaced by the Dumas method, which is faster and does not use dangerous chemicals. Although the
principles of the two methods are different, both measure the nitrogen content of the product. Nitrogen can
be converted into protein content by using an appropriate factor. The value of this factor varies with the
relative amounts of different proteins and their amino-acid composition in the given product.
Neither the Dumas nor the Kjeldahl method distinguishes between protein and non-protein nitrogen. In
most cases, results obtained by the Dumas method are slightly higher than those of the Kjeldahl method.
This is due to the fact that the Dumas method measures almost all of the non-protein nitrogen, whereas the
Kjeldahl method measures only a part of it.
Taking into consideration that the calculated protein content of a product by both methods only approximates
the true value, it is a matter of discretion which one is accepted. The most appropriate solution should be the
use of a second factor for the elimination of the systematic error caused by the non-protein nitrogen content
of the different products. However, this second factor has to be determined for each product, like existing
factors, which show the ratio of the protein to the nitrogen content

v
DRAFT International Standard ISO/DIS 16634-1:2025(en)
Food products - Determination of the total nitrogen content
by combustion according to the Dumas principle and
calculation of the crude protein content —
Part 1:
Oilseeds and animal feeding stuffs
1 Scope
This part of ISO 16634 specifies a method for the determination of the total nitrogen content and the
calculation of crude protein content of oilseeds, oilseeds meals, compound feed, feed raw materials,
premixtures from plant origin, and excreta.
For mineral premixtures and feed additives, the method of determination of the total nitrogen content
described in this International Standard can be used. However, for these 2 matrices, the calculation of the
protein content described in this international standard do not apply.
For excreta, the accuracy of the method has to be checked individually
This method, like the Kjeldahl method, does not distinguish between protein nitrogen and non-protein
nitrogen. For the calculation of protein content, the conversion factors used is 6,25.
This method is not applicable to milk and milk products, for which a method is specified in
[10]
ISO 14891 | IDF 185 .
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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.
ISO 664, Oilseeds — Reduction of laboratory sample to test sample
ISO 665, Oilseeds — Determination of moisture and volatile matter content
ISO 771, Oilseed meals — Determination of moisture and volatile matter content
ISO 6496, Animal feeding stuffs — Determination of moisture and other volatile matter content
ISO 6498, Animal feeding stuffs — Guidelines for sample preparation
ISO 12099, Animal feeding stuffs, cereals and milled cereal products — Guidelines for the application of near
infrared spectrometry
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp

ISO/DIS 16634-1:2025(en)
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
nitrogen content
mass fraction of the total nitrogen determined by the procedure specified in this part of ISO 16634
Note 1 to entry: The mass fraction is expressed as a percentage.
3.2
crude protein content
nitrogen content (3.1) multiplied by a factor, equal to 6,25
3.3
excreta
substances released by the body; nutritional and metabolic waste (faeces, droppings, urine, etc.)
4 Principle
Food samples are combusted (burned) into gas in the furnace adjusted to greater than or equal to 850 °C under
a flow of pure oxygen in a combustion tube and carrier gas. Combusted gasses are swept passing through
copper oxide platinum catalyst to reduce any remining nitrogen oxide to N gas and remove excess oxygen.
Other interfering gas (CO and H O) are removed and then the nitrogen content is quantitatively determined
2 2
using a thermal conductivity detector cell. The nitrogen content is calculated by a microprocessor.
5 Reagents
Use only reagents of recognized analytical grade, or reagents of equivalent purity as specified by instrument
manufacturers. Except for the reference materials (5.12), all reagents shall be free from nitrogen.
5.1 Carrier gas(es): use one of 5.1.1, and 5.1.2 and 5.1.3.
5.1.1 Carbon dioxide, as pure as possible and of minimum volume fraction, ϕ (CO ) ≥ 99,99 %.
5.1.2 Helium, as pure as possible and of minimum volume fraction, ϕ (He) ≥ 99,99 %.
5.1.3 Argon, as pure as possible and of minimum volume fraction, ϕ (Ar) ≥ 99,99 %.
The collaborative data were obtained in the 1990s with helium and carbon dioxide as carrier gas. Some
devices (6.5) can be used with argon as carrier gas. If so, the results obtained with argon shall be verified by
the laboratory.
5.2 Oxygen, as pure as possible and of minimum volume fraction, ϕ(O2) ≥ 99,99 %.
5.3 Sulfur dioxide and halogen absorbent, to eliminate any sulfur from the sample [e.g. lead chromate
(PbCrO4) or steel wool].
5.4 Copper oxide platinum catalyst (filling material for the post-combustion tube).
Platinum catalyst [5 % of Pt on alumina (Al O )] is blended with CuO at a ratio of 1:7 parts or 1:8 parts
2 3
according to the manufacturer's recommendations.
To prevent separation as a result of the different bulk densities of the two materials, it is recommended not
to prepare the mixture before filling the tube. It is advisable to pour the platinum catalyst and copper oxide
simultaneously into the post-combustion tube using a suitable funnel.

ISO/DIS 16634-1:2025(en)
5.5 Silver or copper wool.
This should be disaggregated before being inserted in the post-combustion or reduction tube.
5.6 Silica (quartz) or glass wool or cotton wool, as recommended by the instrument manufacturer.
5.7 Copper (wire, cuttings, turnings or powder), or tungsten for the reduction tube.
The use of copper wires can improve the precision of analytical results for samples with low nitrogen
contents (about 1 % mass fraction).
5.8 Diphosphorus pentoxide (P O ) or granulated magnesium perchlorate [Mg(ClO ) ], or another
2 5 4 2
suitable support material, to fill the drying tubes.
5.9 Hollow corundum spheres or aluminium oxide pellets, for the combustion tube if recommended by
the instrument manufacturer.
5.10 Copper oxide (CuO), as filling material for the combustion tube if recommended by the instrument
manufacturer.
5.11 Sodium hydroxide (NaOH), on a support material.
5.12 Aspartic acid (C H NO ) or ethylenediaminetetraacetic acid (C H N O ) or glutamic acid
4 7 4 10 16 2 8
(C H NO ) or hippuric acid (C H NO ) standard, or other suitable reference materials with known,
5 9 4 9 9 3
constant, certified nitrogen content.
Minimum recovery should be 99 % mass fraction.
5.13 Light petroleum, with boiling range between 30 °C and 60 °C, or acetone or ethanol to clean
quartz tubes.
5.14 Nitrogen-free compound (ex. Sucrose)
6 Apparatus
Usual laboratory equipment and, in particular, the following.
6.1 Analytical balance, capable of weighing to the nearest 0,000 1 g.
6.2 Grinding device, appropriate to the nature of the sample to ensure homogeneity of ground sample.
6.3 Sieve, for grinding device control of nominal opening adapted to grating of the used mill made of
non-ferrous material.
6.4 Crucibles (e.g. made of stainless steel, quartz, ceramic or platinum) or tin capsules or tin foils or
nitrogen-free filter paper for pressing pellets, suitable for the Dumas apparatus used.
NOTE 1 Several commercial instruments are provided with an automatic sampler.
NOTE 2 Some solid samples (e.g. powders) can be pressed to form pellets.

ISO/DIS 16634-1:2025(en)
1)
6.5 Dumas apparatus , fitted with a furnace able to maintain a given temperature greater than or equal
to 850 °C, with a thermal conductivity detector and suitable device for signal integration.
Suitable Dumas apparatus operates according to the general flowchart given in Annex A, although different
arrangements and components may be used.
To avoid leaks, the sealing O-rings shall be slightly lubricated with high-vacuum grease prior to installation.
Experience has shown that it is important to clean all pieces of silica and glassware carefully, and to remove
fingerprints from the tubes using a suitable solvent (e.g. acetone) before inserting them in the furnace.
7 Sampling
A representative sample should have been sent to the laboratory. It should not have been damaged or
changed during transport or storage.
Sampling is not part of the method specified in this part of ISO 16634. Recommended sampling methods are
[1] [3]
given in ISO 542 for oilseeds, in ISO 5500 for oilseed residues, and in ISO 6498 for animal feeding stuffs.
8 Preparation of test sample
The laboratory sample shall be prepared in such a way that a homogeneous test sample is obtained, which is
representative of the oilseeds (see ISO 664) or animal feeding stuff (see ISO 6498).
To check grinded material compliance, particle size and homogeneity shall be controlled.
Using a suitable grinding device (6.2), grind the laboratory sample. To check grinding device, particle size
and homogeneity shall be controlled. Pass the ground material through a sieve (6.3) of nominal opening
[15]
adapted to the grating of the used mill. Mills that produce particle sizes meeting the specifications given
in Table 1 will give acceptable results.
Table 1 — Accepted particule size
Grinding device with a less than 1 mm sieve Grinding device with a 1 mm sieve
Nominal size of sieve Amount passing through Nominal size of sieve Amount passing through
openings sieve openings sieve
µm % mass fraction µm % mass fraction
710 100 > 1 000 100
500 95 to 100 1 000 95 to 100
200 85 or less 500 85 or less
Grinding may result in water loss and therefore the water content of the ground sample should also
be analysed when reporting nitrogen or protein values to dry matter or a constant moisture basis.
Determination of the moisture shall be carried out according to ISO 665 for oilseeds, ISO 771 for oilseeds
meals or ISO 6496 for animal feeding stuffs or by the way of a near infrared apparatus in accordance with
ISO 12099 whose performance has been validated and are consistent with tolerances from reference method
ISO 6496.
The homogeneity of grinded material produced by grinders shall also be verified.
NOTE One possible way to check grinded material homogeneity can be done by replicate preparation of ground
samples of a 2+1 mixture of corn and soya seeds and N determination. The expected coefficient of variation should be
less than 2 % mass fraction.
1) Elementar Analysensysteme, Sumika Chemical Analysis Service, and LECO Instruments produce suitable equipment
available commercially. This information is given for the convenience of users of this International Standard and does not
constitute an endorsement by ISO of this equipment. Equivalent products may be used if they can be shown to lead to the
same results.
...