ISO 24187

Principles for the analysis of microplastics present in the environment

This document describes the principles to be followed in the analysis of microplastics in various environmental matrices. This includes the unique particle size classification of plastics, the use of certain apparatus with regard to sampling, sample preparation, and the determination of representative sample quantities. The purpose of this document is to specify minimum requirements until specific standards for the different case situations are available. This is important to ensure that the development of the specific standards is done on a consistent basis to ensure that comparison or correlation of results is possible. This document does not include requirements for monitoring actions.

Principes d'analyse des microplastiques présents dans l'environnement

Le présent document décrit les principes à suivre pour l’analyse des microplastiques dans diverses matrices environnementales. Cela implique une classification unique de la granulométrie des plastiques, l’utilisation de certains appareillages pour l’échantillonnage, la préparation des échantillons, et la détermination de quantités d’échantillon représentatives. L’objectif du présent document est de spécifier les exigences minimales jusqu’à ce que des normes spécifiques soient disponibles pour les différents cas de figure. Cela est important pour s’assurer que l’élaboration des normes spécifiques est réalisée sur une base cohérente qui garantit que la comparaison ou la corrélation des résultats est possible. Le présent document n’inclut pas d’exigences pour assurer le suivi des actions menées.

General Information

• Status: Not Published
• ICS: 13.020.01 - Environment and environmental protection in general
• ICS: 83.080.01 - Plastics in general
• Technical Committee: ISO/TC 61/SC 14 - Environmental aspects
• Drafting Committee: ISO/TC 61/SC 14/WG 4 - Characterization of plastics leaked into the environment (including microplastics) and quality control criteria of respective methods
• Current Stage: 6000 - International Standard under publication
• Completion Date: 23-Jun-2023

Standards Content (Sample)

ISO/DIS 24187:2021(E)
2022-12-0502-08
ISO/FDIS 24187:20222023
ISO TC 61/SC 14/WG 4
Secretariat: DIN
Principles for the analysis of microplastics present in the environment

---------------------- Page: 1 ----------------------
ISO/FDIS 24187:20222023(E)
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no
part of this publication may be reproduced or utilized otherwise in any form or by any means,
electronic or mechanical, including photocopying, or posting on the internet or an intranet, without
prior written permission. Permission can be requested from either ISO at the address below or
ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.orgwww.iso.org
Published in Switzerland
ii © ISO 2022 – All rights reserved
ii © ISO 2023 – All rights reserved

---------------------- Page: 2 ----------------------
ISO/FDIS 24187:2022(E)
Contents
Foreword . v
Introduction. vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General Aspects . 3
5 General requirements for all analytical steps . 4
6 Identification of appropriate detection methods . 5
6.1 General . 5
6.2 Classification of detection tools . 5
6.3 Identification of addressed objective . 6
7 Sampling of water . 7
7.1 General . 7
7.2 Sampling volume . 7
7.3 Mesh sizes . 7
7.4 Filter materials . 8
7.5 Sampling Devices . 8
8 Sampling of terrestric, semiterrestric and subhydric soils . 8
8.1 General aspects . 8
8.2 Sampling of terrestrial soils . 9
8.3 Sampling of semiterrestrial soils . 9
8.4 Sampling of subhydric soils (sediments) . 9
9 Sampling of air . 9
9.1 Indoor Air . 9
9.2 Outdoor Air . 10
10 Sampling of sludges and other similar materials . 10
11 Sampling of mineral and other inorganic materials . 10
12 Sampling of biota . 10
13 Sample preparation . 11
13.1 General aspects . 11
13.2 Drying . 11
13.3 Milling and grinding . 12
13.4 Removal of inorganic matter . 12
13.5 Removal of organic matter . 12
14 Data Processing . 12
14.1 General Aspects . 12
14.2 Single spectra / chromatogram interpretation . 13
14.3 Interpretation of large spectra / chromatogram datasets . 13
Formatted: Font: 11 pt
15 Aspects of analytical quality assurance . 13
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© ISO 2023 – All rights reserved iii

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ISO/FDIS 24187:20222023(E)
15.1 Reference Materials . 13
15.2 Performance of interlaboratory comparison tests . 15
Annex A (informative) Advanced Data Processing . 17
A.1 Introduction to advanced data processing . 17
A.2 Methods for determining particle number and sizes (Spectroscopic procedures) . 18
A.2.1 Chemical structure determination . 18
A.2.2 Spatial Analysis . 18
A.3 Methods for determining mass content (thermoanalytical and chemical methods) . 19
A.3.1 Chemical structure determination. . 19
A.3.2 Quantification of mass content . 19
A.3.3 General recommendations for evaluating databases and data processing approaches . 20
A.3.4 Classification . 20
A.3.5 Regression . 21
A.4 Data file formats . 21
A.5 A practical example for computing classification performance measures . 21
Bibliography . 23
Foreword . v
Introduction. vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General Aspects . 3
5 General requirements for all analytical steps . 4
6 Identification of appropriate detection methods . 5
6.1 General . 5
6.2 Classification of detection tools . 5
6.3 Identification of addressed objective . 6
7 Sampling of water . 7
7.1 General . 7
7.2 Sampling volume . 7
7.3 Mesh sizes . 7
7.4 Filter materials . 8
7.5 Sampling Devices . 8
8 Sampling of terrestric, semiterrestric and subhydric soils . 8
8.1 General aspects . 8
8.2 Sampling of terrestrial soils . 9
8.3 Sampling of semiterrestrial soils . 9
8.4 Sampling of subhydric soils (sediments) . 9
iv © ISO 2022 – All rights reserved
iv © ISO 2023 – All rights reserved

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ISO/FDIS 24187:2022(E)
9 Sampling of air . 9
9.1 Indoor Air . 9
9.2 Outdoor Air . 10
10 Sampling of sludges and other similar materials . 10
11 Sampling of mineral and other inorganic materials . 10
12 Sampling of biota . 10
13 Sample preparation . 11
13.1 General aspects . 11
13.2 Drying . 11
13.3 Milling and grinding . 12
13.4 Removal of inorganic matter . 12
13.5 Removal of organic matter . 12
14 Data Processing . 12
14.1 General Aspects . 12
14.2 Single spectra / chromatogram interpretation . 13
14.3 Interpretation of large spectra / chromatogram datasets . 13
15 Aspects of analytical quality assurance . 13
15.1 Reference Materials . 13
15.2 Performance of interlaboratory comparison tests . 15
Annex A (informative) Advanced Data Processing . 17
A.1 Introduction to advanced data processing . 17
A.2 Methods for determining particle number and sizes (Spectroscopic procedures) . 18
A.2.1 Chemical structure determination . 18
A.2.2 Spatial Analysis . 18
A.3 Methods for determining mass content (thermoanalytical and chemical methods) . 19
A.3.1 Chemical structure determination. . 19
A.3.2 Quantification of mass content . 19
A.3.3 General recommendations for evaluating databases and data processing approaches . 20
A.3.4 Classification . 20
A.3.5 Regression . 21
A.4 Data file formats . 21
A.5 A practical example for computing classification performance measures . 21
Bibliography . 23

Formatted: Font: 11 pt
Formatted: Line spacing: Exactly 11 pt
© ISO 2022 – All rights reserved v
© ISO 2023 – All rights reserved v

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ISO/FDIS 24187:20222023(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
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/directiveswww.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any
patent rights identified during the development of the document will be in the Introduction and/or on
the ISO list of patent declarations received (see www.iso.org/patentswww.iso.org/patents).
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.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 14,
Environmental aspects, in collaboration with the European Committee for Standardization (CEN)
Technical Committee CEN/TC 249, Plastics, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement).
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.htmlwww.iso.org/members.html.
vi © ISO 2022 – All rights reserved
vi © ISO 2023 – All rights reserved

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ISO/FDIS 24187:2022(E)
Introduction
The analysis of plastics and microplastics is a new field in relation to other areas of environmental
analysis. A large number of scientific publications exist, but they do not apply a uniform analysis, which
makes it difficult to compare the results.
This document sets out key principles for the investigation of microplastics in the environment, which
should be taken into account in the subsequent development of specific procedures for sampling, sample
preparation and detection. A large number of the principles described in this document can be applied,
analogously, to other matrices and products, including foodstuffs and drinking water. The objective is to
present a pool of methods and notes that is as harmonized as possible and to make it available for use in
science, businesses and administrations.
What is true for analytics is also true for definitions in the same way. On the one hand, the terms used in
this document are based on existing definitions in the subject area, but on the other hand, analytical
requirements are also taken into account. This applies, for example, to the term “large microplastics”. The
particle size to be investigated is closely related to the detection method to be selected. In the course of
future specific work, it can be necessary to modify existing definitions slightly and adapt them to new
knowledge and requirements.
With regard to the definitions, including the ideas of size classes, it is pointed out, that the discussion is
ongoing in various technical committees in ISO and other standardization bodies. The definitions in this
document show the status in ISO TC 61/SC 14. The definitions chosen in this document are adapted from
the ISO report on plastics. The basis of the classification is based on the metric sizes and the associated
designations. Microplastics is thus derived from micrometres.
NOTE Microplastics can also stem from different sources not specifically mentioned in this document, such as
textiles, paints and tyres.
Formatted: Font: 11 pt
Formatted: Line spacing: Exactly 11 pt
© ISO 2022 – All rights reserved vii
© ISO 2023 – All rights reserved vii

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FINAL DRAFT INTERNATIONAL STANDARD ISO/DISFDIS 24187:20222023(E)

Principles for the analysis of microplastics present in the
environment
1 Scope
This document describes the principles to be followed in the analysis of microplastics in various
environmental matrices. This includes the unique particle size classification of plastics, the use of certain
apparatus with regard to sampling, sample preparation, and the determination of representative sample
quantities.
The purpose of this document is to specify minimum requirements until specific standards for the
different case situations are available. This is important to ensure that the development of the specific
standards is done on a consistent basis to ensure that comparison or correlation of results is possible.
This document does not include requirements for monitoring actions.
2 Normative references
There are no normative references in this document.
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 472, Plastics — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 and the following 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/obphttps://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
3.1
large microplastic
any solid plastic particle insoluble in water with any dimension between 1 mm and 5 mm
Note 1 to entry: Microplastics may show various shapes.
Note 2 to entry: Typically, a large microplastics object represents an item consisting of plastics or a part of an end-
Formatted: Font: 11 pt
user product or a fragment of the respective item.
Formatted: Line spacing: Exactly 11 pt
© ISO 2022 – All rights reserved 1
© ISO 2022 – All rights reserved 1

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ISO/FDIS 24187:20222023(E)
[SOURCE: ISO/TR 21960:2020, 3.10, modified — term number in Note 1 to entry was removed.]
3.2
microplastic
any solid plastic particle insoluble in water with dimension between 1 µm and 1 000 µm (= 1 mm)
Note 1 to entry: Primary microplastics object represents a particle intentionally added to end-user products for
example cosmetic means, coatings, paints etc. Secondary microplastics object can also result as a fragment of the
respective item.
Note 2 to entry: Microplastics have regular and irregular shapes (see ISO 9276-6:20172008).
Note 3 to entry: The defined dimension is related to the longest length of the particle.
[SOURCE: ISO/TR 21960:2020, 3.9, modified — Note 1 to entry was removed, all other Notes to entry
were changed.]
3.3
additives
substances which are used to process plastics or to modify end use properties of plastics
Note 1 to entry: Important additives such as fillers/reinforced materials, softeners and flame retardants are
referenced according to ISO 1043-2 to ISO 1043-4.
4 General aspects
Microplastics is a term that comes along with different physical and chemical properties, such as shape,
size (range), type of polymer(s), presence of additives, presence of fillers, state of degradation and so on.
The amount of microplastics in a given matrix can be measured in different ways, i.e. as number (of
particles) or mass content/fraction in relation to the sample’s quantity, which itself can be based on
various units (volume, weight, etc.). Hence, before selecting a suitable (set of) method(s), the question(s)
to be answered and properties to be measured need to be specified carefully. This applies not only to
detection methods but also to the sampling and processing/preparation methods associated with them,
right up to the statistical evaluation of results.
A schematic representation of the interdependencies of microplastics analysis is shown in Figure 1. As a
rule, the objective or objectives of a measurement or a measurement program is/ are based on a clear
question/task or on an evaluation concept involving necessary assessment parameters, respectively (for
example integration into an overall ecological context, thresholds for monitoring). A suitable detection
method is then selected, which generates the desired result parameters (such as polymer type, mass
content, number, shape, size, degradation status).
2 © ISO 2022 – All rights reserved
2 © ISO 2023 – All rights reserved

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ISO/FDIS 24187:20222023(E)


Figure 1 — Schematic representation of interdependencies during microplastics analysis in
environmental and related matrices
5 General requirements for all analytical steps
All analytical steps (sampling, sample preparation, detection) shall be undertaken in plastics-free or low-
plastics working conditions. These include the avoidance of standard plastics products (for example
tubes, vessels). Contamination, especially cross-contamination shall be avoided, the user should avoid
using plastics equipment wherever possible. Instead, alternatives made of metal, glass or ceramics should
be used. As an exception and after it was proved by experiments (for example by characterizing the
container), types of plastics that are not to be detected or evaluated can be used as well. Care should be
taken that also personal protective equipment (e.g. lab coats, gloves) are also made of non-synthetic
material or material that does not interfere with the analyses. Recovery tests should be performed for
each analytical step.
If feasible, samples should be handled in laminar flow boxes in the laboratory or clean rooms (class 3
according to ISO 14644-1, especially during the preparation process of samples and during the
determination of particle numbers.
It shall be determined beforehand, whether a hygienization of samples is necessary. Sterilization is a
Formatted: Font: 11 pt
standard recommendation for the analysis of dry samples from wastewater, sewage sludge and organic
Formatted: Line spacing: Exactly 11 pt
© ISO 2022 – All rights reserved 3
© ISO 2023 – All rights reserved 3

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ISO/F
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 24187
ISO/TC 61/SC 14
Principles for the analysis of
Secretariat: DIN
microplastics present in the
Voting begins on:
2023-02-23 environment
Voting terminates on:
Principes d'analyse des microplastiques présents dans
2023-04-20
l'environnement
ISO/CEN PARALLEL PROCESSING
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 SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 24187:2023(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO 2023

---------------------- Page: 1 ----------------------
ISO/FDIS 24187:2023(E)
FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 24187
ISO/TC 61/SC 14
Principles for the analysis of
Secretariat: DIN
microplastics present in the
Voting begins on:
environment
Voting terminates on:
Principes d'analyse des microplastiques présents dans
l'environnement
COPYRIGHT PROTECTED DOCUMENT
© ISO 2023
ISO/CEN PARALLEL PROCESSING
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
RECIPIENTS OF THIS DRAFT ARE INVITED TO
ISO copyright office
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
CP 401 • Ch. de Blandonnet 8
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
CH-1214 Vernier, Geneva
DOCUMENTATION.
Phone: [phone]
IN ADDITION TO THEIR EVALUATION AS
Reference number
Email: [e-mail]
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/FDIS 24187:2023(E)
Website: www.iso.org
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
Published in Switzerland
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN­
DARDS TO WHICH REFERENCE MAY BE MADE IN
ii
  © ISO 2023 – All rights reserved
NATIONAL REGULATIONS. © ISO 2023

---------------------- Page: 2 ----------------------
ISO/FDIS 24187:2023(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General aspects . 2
5 General requirements for all analytical steps . 2
6 Identification of appropriate detection methods . 3
6.1 General . 3
6.2 Detection techniques . 4
6.3 Identification of objective to be addressed . 4
7 Sampling of water . 5
7.1 General . 5
7.2 Sampling volume . 5
7.3 Mesh sizes . 6
7.4 Filter materials . 6
8 Sampling of terrestrial, semiterrestrial and subhydric soils . 6
8.1 General . 6
8.2 Sampling of terrestrial soils . 6
8.3 Sampling of semiterrestrial soils . 7
8.4 Sampling of subhydric soils (sediments) . 7
9 Sampling of air . 7
9.1 Indoor air . 7
9.2 Outdoor air . 7
10 Sampling of sludges and other similar materials . 7
11 Sampling of mineral and other inorganic materials . 8
12 Sampling of biota . 8
13 Sample preparation .8
13.1 General aspects . 8
13.2 Drying . 9
13.3 Milling and grinding . 9
13.4 Removal of inorganic matter . 9
13.5 Removal of organic matter . 9
14 Data processing .10
14.1 General aspects . 10
14.2 Single spectra/chromatogram interpretation . 10
14.3 Interpretation of large spectra/chromatogram data sets . 10
15 Aspects of analytical quality assurance .11
15.1 Reference materials . 11
15.2 Performance of interlaboratory comparison tests.12
Annex A (informative) Advanced Data Processing .14
Bibliography .20
iii
© ISO 2023 – All rights reserved

---------------------- Page: 3 ----------------------
ISO/FDIS 24187:2023(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
committee has been established has the right to be represented on that committee. International
organizations, governmental and non­governmental, 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
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 61, Plastics, Subcommittee SC 14,
Environmental aspects, in collaboration with the European Committee for Standardization (CEN)
Technical Committee CEN/TC 249, Plastics, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement).
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 2023 – All rights reserved

---------------------- Page: 4 ----------------------
ISO/FDIS 24187:2023(E)
Introduction
The analysis of plastics and microplastics is a new field in relation to other areas of environmental
analysis. A large number of scientific publications exist, but they do not apply a uniform analysis, which
makes it difficult to compare the results.
This document sets out key principles for the investigation of microplastics in the environment, which
should be taken into account in the subsequent development of specific procedures for sampling, sample
preparation and detection. A large number of the principles described in this document can be applied,
analogously, to other matrices and products, including foodstuffs and drinking water. The objective is
to present a pool of methods and notes that is as harmonized as possible and to make it available for use
in science, businesses and administrations.
What is true for analytics is also true for definitions in the same way. On the one hand, the terms used
in this document are based on existing definitions in the subject area, but on the other hand, analytical
requirements are also taken into account. This applies, for example, to the term “large microplastics”.
The particle size to be investigated is closely related to the detection method to be selected. In the
course of future specific work, it can be necessary to modify existing definitions slightly and adapt
them to new knowledge and requirements.
With regard to the definitions, including the ideas of size classes, it is pointed out, that the discussion
is ongoing in various technical committees in ISO and other standardization bodies. The definitions in
this document show the status in ISO TC 61/SC 14. The definitions chosen in this document are adapted
from the ISO report on plastics. The basis of the classification is based on the metric sizes and the
associated designations. Microplastics is thus derived from micrometres.
NOTE Microplastics can also stem from different sources not specifically mentioned in this document, such
as textiles, paints and tyres.
v
© ISO 2023 – All rights reserved

---------------------- Page: 5 ----------------------
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 24187:2023(E)
Principles for the analysis of microplastics present in the
environment
1 Scope
This document describes the principles to be followed in the analysis of microplastics in various
environmental matrices. This includes the unique particle size classification of plastics, the use of
certain apparatus with regard to sampling, sample preparation, and the determination of representative
sample quantities.
The purpose of this document is to specify minimum requirements until specific standards for the
different case situations are available. This is important to ensure that the development of the specific
standards is done on a consistent basis to ensure that comparison or correlation of results is possible.
This document does not include requirements for monitoring actions.
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 472, Plastics — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 and the following 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 https:// www .electropedia .org/
3.1
large microplastic
any solid plastic particle insoluble in water with any dimension between 1 mm and 5 mm
Note 1 to entry: Microplastics may show various shapes.
Note 2 to entry: Typically, a large microplastics object represents an item consisting of plastics or a part of an
end­user product or a fragment of the respective item.
[SOURCE: ISO/TR 21960:2020, 3.10, modified — term number in Note 1 to entry was removed.]
3.2
microplastic
any solid plastic particle insoluble in water with dimension between 1 µm and 1 000 µm (= 1 mm)
Note 1 to entry: Primary microplastics object represents a particle intentionally added to end-user products for
example cosmetic means, coatings, paints etc. Secondary microplastics object can also result as a fragment of the
respective item.
Note 2 to entry: Microplastics have regular and irregular shapes (see ISO 9276-6:2008).
Note 3 to entry: The defined dimension is related to the longest length of the particle.
1
© ISO 2023 – All rights reserved

---------------------- Page: 6 ----------------------
ISO/FDIS 24187:2023(E)
[SOURCE: ISO/TR 21960:2020, 3.9, modified — Note 1 to entry was removed, all other Notes to entry
were changed.]
3.3
additives
substances which are used to process plastics or to modify end use properties of plastics
Note 1 to entry: Important additives such as fillers/reinforced materials, softeners and flame retardants are
referenced according to ISO 1043­2 to ISO 1043­4.
4 General aspects
Microplastics is a term that comes along with different physical and chemical properties, such as shape,
size (range), type of polymer(s), presence of additives, presence of fillers, state of degradation and so
on. The amount of microplastics in a given matrix can be measured in different ways, i.e. as number
(of particles) or mass content/fraction in relation to the sample’s quantity, which itself can be based on
various units (volume, weight, etc.). Hence, before selecting a suitable (set of) method(s), the question(s)
to be answered and properties to be measured need to be specified carefully. This applies not only
to detection methods but also to the sampling and processing/preparation methods associated with
them, right up to the statistical evaluation of results.
A schematic representation of the interdependencies of microplastics analysis is shown in Figure 1. As
a rule, the objective or objectives of a measurement or a measurement program is/ are based on a clear
question/task or on an evaluation concept involving necessary assessment parameters, respectively
(for example integration into an overall ecological context, thresholds for monitoring). A suitable
detection method is then selected, which generates the desired result parameters (such as polymer
type, mass content, number, shape, size, degradation status).
Figure 1 — Schematic representation of interdependencies during microplastics analysis in
environmental and related matrices
5 General requirements for all analytical steps
All analytical steps (sampling, sample preparation, detection) shall be undertaken in plastics-free
or low­plastics working conditions. These include the avoidance of standard plastics products (for
example tubes, vessels). Contamination, especially cross-contamination shall be avoided, the user
should avoid using plastics equipment wherever possible. Instead, alternatives made of metal, glass
or ceramics should be used. As an exception and after it was proved by experiments (for example by
characterizing the container), types of plastics that are not to be detected or evaluated can be used as
well. Care should be taken that personal protective equipment (e.g. lab coats, gloves) are also made of
non-synthetic material or material that does not interfere with the analyses. Recovery tests should be
performed for each analytical step.
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If feasible, samples should be handled in laminar flow boxes in the laboratory or clean rooms (class 3
according to ISO 14644-1, especially during the preparation process of samples and during the
determination of particle numbers.
It shall be determined beforehand whether hygienization of samples is necessary. Sterilization is a
standard recommendation for the analysis of dry samples from wastewater, sewage sludge and organic
wastes. Various methods can be applied, but each of them has specific impact on the integrity of
microplastics particles in the sample.
a) Steam sterilization: risk of melting microplastics (for example PE, PP).
b) Radiation sterilization (gamma, beta radiation, UV radiation): risk that the polymer structure is
degraded (cleavage of polymer chains and oxidation).
c) Chemical sterilization: risk that polymer structure or the particles’ surface is chemically modified.
Relevant information about the measurement conditions and control processes (quality assessment
and quality control/QAQC) shall be recorded, including all analytical steps. For general quality control
measures in laboratories, see ISO/IEC 17025:2017. For intercomparison tests, see ISO 13528.
Blank value determination for the applied detection methods is essential, since contamination
(for example by airborne particles) during sampling, preparation and detection can easily occur.
Determination of blank values is essential; the number of blanks depends on the concrete method to be
applied. More specific requirements have to be given in upcoming standards.
A classification of microplastics into size classes according to Table 1 is recommended. Small particles
that occur in higher quantities are grouped into narrower classification classes than the larger particles,
which are more relevant in terms of mass and classified into wider classes. This also enables a higher
methodological feasibility of processes (including feasibility of filtration, detection limits in analytics)
and a better integration of particle quantities/masses in impact analyses (i.e. for environmental
assessments). The proposed size classes are given in Table 1. The maximum dimension/diameter/
length of a particle defines the size class.
Table 1 — Particle size classification
Large mi-
Classification Microplastics
croplastics
particle size 100 to 500 to
μm 1 to < 5 5 to < 10 10 to < 50 50 to < 100 1 000 to 5 000
classes < 500 < 1 000
average par­
μm 3 7,5 30 75 300 750 3 000
ticle size
a −8 −7 −5 −4
mass mg 1,4 × 10 2,2 × 10 1,4 × 10 2,2 × 10 0,014 0,22 14
number of
9 7 6 4
particles in number 1,0 × 10 6,4 × 10 1,0 × 10 6,4 × 10 1 000 64 1
14,13 mg
a
Mass here is estimated from the average particle size (3 000 µm) assuming spherical particle with a density of 1.
6 Identification of appropriate detection methods
6.1 General
The selection of one or more quantitative or qualitative detection method(s) depends specifically on
the objectives and tasks of a project or an existing requirement. The various detection methods differ
regarding the generated result per measurement. These include identification of the polymer (type of
polymer) and other qualitative properties (i.e. presence of additives, chemical composition, molecular
weight and morphology of particle surface, particle size and shape) and quantitative properties
(particle number, particle mass fraction).
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Depending on the objective of the analysis, it can be sufficient to apply a (pre-)screening method
that may give limited information, but does not require sophisticated instrumentation. For (pre-)
screening purposes relatively simple and inexpensive techniques could be used. Like this, cost-effective
routine analyses can be carried out with a higher throughput than more performance but highly time
consuming and costly techniques.
6.2 Detection techniques
Different detection methods based on various measurement principles are available for microplastics
analysis.
Spectroscopic methods can capture and assign the characteristics of specific chemical structures of
polymers using reference spectra. Used methods are based on vibrational spectroscopy techniques
(including on microscopic level) including different measurement setups:
— Fourier transform infrared spectroscopy (FTIR);
— attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR);
— focal plan array detector Fourier transform infrared spectroscopy (FPA-FTIR);
— quantum cascade laser induced infrared spectroscopy (QCL-IR);
— near or short-wave infrared spectroscopy (NIR, SWIR);
— Raman spectroscopy.
In thermo-analytical methods, the sample is pyrolysed under inert conditions and specific
decomposition products of the individual polymers are detected. Currently well-established are gas
chromatography-mass spectrometry (GC-MS) methods. They differ regarding the heating procedure
(filament based, micro furnace, Curie point), the sample amounts or sample preparation of individual
selected or concentrated particles (pyrolysis - Py-GC-MS) as well as pyrolysis of complete filter residues
(thermal extraction desorption - TED-GC-MS). Further methods are suitable, an alternative is the use of
methods, which detect the specific melting process of semi-crystalline polymer materials (differential
scanning calorimetry, DSC).
Chemical methods are used to decompose the samples and detect specific fragments of polymers or
elements. Examples are inductively coupled plasma mass spectrometry (ICP-MS) for tyre and road
wear particles or liquid chromatography (LC) for PET, PC or PA, respectively.
Further methods are suitable, such as visual sorting of larger items using microscopy or hot needle test
Such visual sorting is subjective and depends on the expertise of the experimenter. An alternative is
also the detection of dyed particles by fluorescence microscopy and spectroscopy. These methods are
(partly) restricted regarding the analytical accuracy of polymeric particles but represent fast screening
solutions.
All the tools differ regarding the preparation of the samples, the maximum number and sizes of
measurable particles or sample mass, the measurement time and the lower detection level regarding
the lateral resolution or limit.
6.3 Identification of objective to be addressed
Mass content is a monitoring parameter used to estimate the occurrence of microplastics. They
are suitable when it comes to the regular, repeated determination of microplastics in the context of
monitoring and the control of the effectiveness of measures against plastics inputs. The nominal range
of particle size for which these detection analyses are to be made shall be defined in advance. This
grouping into size classes (Table 1) makes it possible to assign the total contents to a specific particle
size range. The contents of the different plastics can be measured in a consistent way, regardless of
particle shape, number and size. In principle, it should be taken into account that a few large particles
are more significant in terms of mass balance than many small particles.
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Determining the exact number, size and shape of particles provides a very comprehensive, detailed
picture of the occurrence of microplastics in environmental samples. This is important for toxicological
studies and assessment. The suitability of the measurement technique for the nominal particle size
range to be investigated shall be ensured in advance. For spectroscopic results it is possible to evaluate
the particle size during or after measurement. The particles of the different plastics can thereby be
measured in a consistent way according to particle shape, number and size. Classification into size
classes (see Table 1) allows for comparing the total contents for a specific particle size range. The
analysis of very small particles (<5 μm) is complex and partly limited for real samples. The evaluation
methods shall guarantee homogeneity of the analysed environmental sample aliquots, as often only a
fraction of the sample can be analysed.
The individual characterization of specific properties of identified plastics particles, for example the
state of degradation, the surface structure or condition, and the analysis of additives can be relevant for
evaluating the interaction with the environment, but also for assessing their sources, entry paths, and
fate. Such analyses may require prior, and in some cases very complex, isolation of individual particles.
7 Sampling of water
7.1 General
Determination of microplastics in the various environmental matrices are a relatively new field of
research. In the following, reference is made to
...