Textiles -- Determination of stable nitrogen isotope ratio in cotton fibres

This document specifies the determination of the ratio of nitrogen isotopes in cotton fibres that are used for textile production. It applies not only to cotton textiles but also to raw cotton taken from cotton fields.

Textiles -- Détermination du rapport isotopique stable de l'azote dans les fibres de coton

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Status
Published
Publication Date
30-Jan-2019
Current Stage
6060 - International Standard published
Start Date
01-Jan-2019
Completion Date
31-Jan-2019
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ISO 20921:2019 - Textiles -- Determination of stable nitrogen isotope ratio in cotton fibres
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INTERNATIONAL ISO
STANDARD 20921
First edition
2019-02
Textiles — Determination of stable
nitrogen isotope ratio in cotton fibres
Textiles — Détermination du rapport isotopique stable de l'azote
dans les fibres de coton
Reference number
ISO 20921:2019(E)
ISO 2019
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ISO 20921:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

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Published in Switzerland
ii © ISO 2019 – All rights reserved
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ISO 20921:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 2

5 Reagent ........................................................................................................................................................................................................................... 2

6 Apparatus ..................................................................................................................................................................................................................... 2

7 Preparation ................................................................................................................................................................................................................ 3

7.1 Sampling of test specimen ............................................................................................................................................................ 3

7.2 Pre-treatment of test specimen ................................................................................................................................................ 3

8 Test procedure ........................................................................................................................................................................................................ 3

8.1 Weighing of aliquot ............................................................................................................................................................................. 3

8.1.1 Determination of weighing amount needed ............................................................................................ 3

8.1.2 General weighing procedure ................................................................................................................................. 3

8.2 Natural N abundance analysis .............................................................................................................................................. 4

8.2.1 Instrumentation ............................................................................................................................................................... 4

8.2.2 General analytical procedure ................................................................................................................................ 4

9 Precision ....................................................................................................................................................................................................................... 5

10 Test report ................................................................................................................................................................................................................... 5

Annex A (normative) Identification procedure of organic raw cotton fibres by using stable

nitrogen isotope ratios ................................................................................................................................................................................... 6

Annex B (informative) Analytical results of cotton fibres of various origin and process stage ..............8

Bibliography .............................................................................................................................................................................................................................10

© ISO 2019 – All rights reserved iii
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ISO 20921:2019(E)
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

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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).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

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.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 38, Textiles.

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 2019 – All rights reserved
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ISO 20921:2019(E)
Introduction

Nitrogen (N) is the most essential element for cotton fibre production, since cotton crops require large

amounts of N to sustain their growth and productivity. For this purpose, considerable amounts of

nitrogen are applied to the soil as chemical fertilizers (e.g. urea) or organic fertilizers (e.g. composted

manure).

The nitrogen applied in the form of a chemical fertilizer or a composted manure is absorbed from the

soil to cotton crops through their root systems during cultivation, leaving a fertilizer-specific nitrogen

isotopic signature in cotton tissues (particularly in cotton fibres). The inerasable nitrogen isotopic

fingerprint engraved in cotton fibres remains unchanged during manufacturing of yarns, textiles and

fabrics.

This document employs the principle of nitrogen isotope discrimination that fractionates against N

15 15

(heavier nitrogen isotope), resulting in N-enriched reactants and N-depleted products. In general,

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composted manure has a much higher δ N (natural N abundance, defined hereinafter) than chemical

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fertilizer due to faster NH (ammonia) volatilization of the lighter nitrogen isotope ( N) than N during

the composting process. In contrast, chemical fertilizers (e.g. urea) are produced from the atmospheric

N via the Haber-Bosch process, resulting in low δ N values close to atmospheric N , which means that

2 2

similar isotopic nitrogen compositions of chemical fertilizers to the atmospheric N .

Organic farming strictly bans the use of genetically modified crops (GMO), synthetic pesticides, and

chemical fertilizers. Therefore, the use of chemical fertilizer during organic cotton production can be

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detected by determining δ N of cotton fibres, since the difference in δ N values between the two

isotopically different nitrogen inputs (chemical vs. organic fertilizers) leaves a fertilizer-specific

isotopic fingerprint in cotton fibres that can thereafter provide a forensic evidence for organic cotton

fibre production.
© ISO 2019 – All rights reserved v
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INTERNATIONAL STANDARD ISO 20921:2019(E)
Textiles — Determination of stable nitrogen isotope ratio
in cotton fibres
1 Scope

This document specifies the determination of the ratio of nitrogen isotopes in cotton fibres that are

used for textile production. It applies not only to cotton textiles but also to raw cotton taken from

cotton fields.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
stable isotope

atom whose nucleus contains the same number of protons but a different number of neutrons

Note 1 to entry: Stable isotopes do not decay into other elements, while radioactive isotopes are unstable and

will decay into other elements.
3.2
isotope-ratio mass spectrometry
IRSM

specialization of mass spectrometry, in which mass spectrometric methods are used to measure the

relative abundance of isotopes in given sample

Note 1 to entry: The analysis of isotopes is normally related to measuring isotopic variations caused by mass-

dependent isotopic fractionation in natural systems.
3.3
isotopic fractionation
isotopic discrimination
process that affect the relative abundance of isotopes

Note 1 to entry: Normally, the focus is on stable isotopes (3.1) of the same element. Isotopic fractionation in the

natural environment can be measured by isotope analysis, using isotope-ratio mass spectrometry, to separate

different element isotopes on the basis of their mass-to-charge ratios.

Note 2 to entry: Both heavy and light stable isotopes participate freely in biochemical reactions and in

geochemical processes, but the rate at which heavy and light stable isotopes react differs. As a result, the lighter

isotopes react faster than the heavier isotopes leading to isotopic fractionation between reactant and product in

the reactions.
© ISO 2019 – All rights reserved 1
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ISO 20921:2019(E)
3.4
natural N abundance
relative amount of the isotopes of nitrogen, as it occurs in nature

Note 1 to entry: Natural N abundance is expressed in parts per thousand (‰, per mil) deviations from the

atmospheric N (a standard).
4 Principle

Isotope-ratio mass spectrometry (IRMS) measures the relative abundance of stable isotopes (e.g. N

and N for nitrogen) in a cotton fibre sample. The abundance of stable isotopes varies according to

physical, physiological and biochemical isotopic fractionation processes. Consequently, variations in

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the isotopic ratio of nitrogen (i.e. N/ N) can be used both as fingerprints of the nitrogen source and

to track the fate and transformation of nitrogen-containing compounds.

Nitrogen (N) is the most essential element that can increase the production of cotton fibres that are

used to manufacture cotton yarns, textiles and fabrics. To ensure cotton fibre production, sufficient

amount of nitrogen should be supplied as fertilizers (chemical or organic fertilizers) to the soil to meet

the nitrogen demand for the growth and productivity of cotton crops.

Since most of fertilizer-nitrogen released into the soil is absorbed through root systems, translocated,

and stored in the cotton fibres during cultivation, the isotopic nitrogen composition of the cotton fibre,

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expressed as δ N, reflects the type of fertilizer from which it originated. In general, δ N of chemical

fertilizers is close to 0 ‰, ranging from −3,9 ‰ to +0,5 ‰, while that of composted manure is much

higher, ranging between +15,4 ‰ and +19,4 ‰. Cotton fibres harvested are processed to produce cotton

yarns, textiles, and fabrics. Therefore, it is believed that δ N of a cotton fibre that contains information

about the type of nitrogen fertilizers can serve as an isotopic fingerprint to identify authenticity and

trace origin of cotton products, such as yarns, textiles and fabrics.

An accurate measurement of δ N of an aliquot of the dried cotton fibres can be obtained by using a

continuous-flow type isotope ratio mass spectrometer li
...

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