EN ISO 24187:2023

Principles for the analysis of microplastics present in the environment (ISO 24187:2023)

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.

Grundsätze für die Analyse von Mikroplastik in der Umwelt (ISO 24187:2023)

Dieses Dokument beschreibt die Grundsätze, die bei der Analyse von Mikrokunststoffen in verschiedenen Umweltmatrizes zu befolgen sind. Dazu gehören die Größenklassifizierung einzelner Kunststoffpartikel, die Verwendung bestimmter Apparaturen für die Probenahme, Probenaufbereitung und die Bestimmung von repräsentativen Probenmengen.
Zweck dieses Dokuments ist es, Mindestanforderungen festzulegen, bis spezifische Normen für die verschiedenen Fallsituationen verfügbar sind. Dies ist wichtig, um sicherzustellen, dass die Entwicklung der spezifischen Normen auf einer konsistenten Grundlage erfolgt, um sicherzustellen, dass ein Vergleich oder eine Korrelation von Ergebnissen möglich ist.
Dieses Dokument enthält keine Anforderungen für Überwachungsmaßnahmen.

Principes d'analyse des microplastiques présents dans l'environnement (ISO 24187:2023)

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.

Načela za analizo mikroplastike v okolju (ISO 24187:2023)

Oblikovanje tehničnih načel, ki se bodo vsesplošno uporabljala za prihodnje standardizacijske
projekte o preskusnih metodah za plastiko in mikroplastiko v različnih matricah (zlasti v vodi, zemlji,
kompostu, blatu iz čistilnih naprav, živih organizmih). To vključuje:
– opis potrebnih delovnih pogojev v laboratoriju;
– opis potrebnih delovnih pogojev na terenu;
– varnostna navodila;
– predloge za uskladitev razredov velikosti, ki jih je treba upoštevati;
– predloge za uskladitev navedbe rezultatov;
– opombe o posebnih značilnostih matric v zvezi z reprezentativnostjo rezultatov.

General Information

• Status: Published
• Publication Date: 26-Sep-2023
• ICS: 13.020.01 - Environment and environmental protection in general
• ICS: 83.080.01 - Plastics in general
• Technical Committee: CEN/TC 249 - Plastics
• Drafting Committee: CEN/TC 249 - Plastics
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 27-Sep-2023
• Completion Date: 27-Sep-2023
• Ref Project: SIST EN ISO 24187:2023 - Principles for the analysis of microplastics present in the environment (ISO 24187:2023)

Overview

EN ISO 24187:2023 - Principles for the analysis of microplastics present in the environment is a CEN-endorsed ISO standard that establishes overarching principles for analysing microplastics across environmental matrices. Published in 2023 (ISO 24187:2023 / EN ISO 24187:2023), it sets minimum requirements for sampling, sample preparation, detection and representative sampling quantities to promote harmonized, comparable results while specific method standards are developed. The document is a principles guide - it does not specify monitoring programs and is intended to support consistent development of future, matrix-specific standards.

Key topics and technical requirements

• Scope and purpose: Defines the analytical framework and minimum requirements for microplastics analysis in various environmental matrices until specific standards exist.
• Particle size classification: Establishes the basis for plastic particle size classes relevant to microplastics analyses (definitions adapted from ISO/TR 21960:2020).
• Sampling guidance: Principles for sampling of water, terrestrial/semiterrestrial/subhydric soils (sediments), indoor/outdoor air, sludges, mineral/inorganic materials and biota. Includes considerations for sample volumes, mesh sizes and filter materials.
• Sample preparation: General requirements and treatments such as drying, milling/grinding, removal of inorganic and organic matter to produce representative analytical samples.
• Detection and identification: Guidance on selecting appropriate detection techniques and aligning method choice with the analytical objective (single-particle vs. bulk analysis).
• Data processing: Principles for interpreting individual spectra/chromatograms and managing large datasets, with an informative annex on advanced data processing.
• Analytical quality assurance: Emphasis on use of reference materials and conducting interlaboratory comparison tests to validate methods and ensure result comparability.
• Limitations: The standard explicitly excludes requirements for monitoring programs.

Practical applications and users

EN ISO 24187:2023 is practical for:

• Environmental and analytical laboratories developing or validating microplastics methods
• Researchers conducting comparative studies across matrices (water, soil, air, biota, sludge)
• Regulatory agencies and policymakers defining evidence-based sampling and analysis frameworks
• Industry and consultants preparing environmental assessments or method SOPs
• Standard developers creating matrix-specific microplastics test methods

By providing harmonised principles, this standard helps ensure that sampling and laboratory workflows are consistent enough to allow comparison and correlation of microplastics data across studies and jurisdictions.

Related standards

• ISO/TR 21960:2020 - source for several definitions and size-class concepts used in EN ISO 24187:2023.
• EN ISO 24187:2023 is a principles-level document intended to support the subsequent development of specific analytical standards for microplastics.

Standards Content (Sample)

SLOVENSKI STANDARD
01-december-2023
Načela za analizo mikroplastike v okolju (ISO 24187:2023)
Principles for the analysis of microplastics present in the environment (ISO 24187:2023)
Grundsätze für die Analyse von Mikroplastik in der Umwelt (ISO 24187:2023)
Principes d'analyse des microplastiques présents dans l'environnement (ISO
24187:2023)
Ta slovenski standard je istoveten z: EN ISO 24187:2023
ICS:
13.020.01 Okolje in varstvo okolja na Environment and
splošno environmental protection in
general
83.080.01 Polimerni materiali na Plastics in general
splošno
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 24187
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2023
EUROPÄISCHE NORM
ICS 13.020.01; 83.080.01
English Version
Principles for the analysis of microplastics present in the
environment (ISO 24187:2023)
Principes d'analyse des microplastiques présents dans Grundsätze für die Analyse von Mikroplastik in der
l'environnement (ISO 24187:2023) Umwelt (ISO 24187:2023)
This European Standard was approved by CEN on 23 July 2023.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 24187:2023 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 24187:2023) has been prepared by Technical Committee ISO/TC 61 "Plastics"
in collaboration with Technical Committee CEN/TC 249 “Plastics” the secretariat of which is held by SIS.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by March 2024, and conflicting national standards shall
be withdrawn at the latest by March 2024.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 24187:2023 has been approved by CEN as EN ISO 24187:2023 without any modification.

INTERNATIONAL ISO
STANDARD 24187
First edition
2023-09
Principles for the analysis of
microplastics present in the
environment
Principes d'analyse des microplastiques présents dans
l'environnement
Reference number
ISO 24187:2023(E)
ISO 24187:2023(E)
© ISO 2023
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]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 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 Sample 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 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 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 document 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 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 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 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 are 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 idea of size classes, it is pointed out that 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 ISO/TR 21960:2020. 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
INTERNATIONAL STANDARD ISO 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 terminology 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
end-user 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.
ISO 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 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).
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 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.
ISO 24187:2023(E)
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. 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. 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
Classification Microplastics
microplastics
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).
ISO 24187:2023(E)
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 plane 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. It is 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.
ISO 24187:2023(E)
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 is a relatively new field of
research. In the following, reference is made to existing standards, some of which, however, were not
developed for microplastics sampling. They give a first indication of the procedure. Microplastics are
similar in shape, size and density to natural particles. However, a 1:1 transfer of the previous procedure
has not yet been realized.
In principle, there are a large number of references in the ISO 5667 series (ISO 5667-1, ISO 5667-4,
ISO 5667-6, ISO 5667-8, ISO 5667-9 and ISO 5667-17) of standards for the sampling of water. This
includes the sampling of fresh waters (for example lakes, rivers and ground waters) and marine waters.
However, these International Standards have not been developed specifically for the sampling of
microplastics. These Internationals Standards are a good basis but shall be examined in detail for their
suitability in relation to the issues at hand and, where appropriate, adapted as necessary. Refrigerating
(max. 4 °C) of samples is recommended in order to avoid microbiological growth, to slow degradation of
samples by bacteria and to extend storage time.
For macroplastics, other sample strategies shall be applied, further developed and validated.
7.2 Sample volume
The sample volume depends on the detection and/or quantification limit of the selected analysis
technique, the expected particle number or mass content of the microplastics under investigation as well
as the size range of the microplastics under investigation: it is assumed that the smaller the diameter
of the particle, the more of them are present in the environmental medium under investigation (for
example in water). In this respect, a smaller sample volume may be sufficient if many small particles are
present and particles are counted in the detection method. For detection methods determining mass
contents, the mass of particle must be sufficient to reach limit of detection or limit of quantification,
respectively.
The lower the particle content, the more sample volume is required in order to examine both sufficient
mass and a sufficient number of particles.
The sample volume in the lower μm range (this means approximately < 10 µm) can be smaller (in the
millilitre or litre range) because the statistical probability of obtaining a representative cross-section
of small particles expected is greater with a high number of particles. However, the present particles
in such a sample must reach the limit of detection/limit of quantification for detection. If the entire
size range down to the upper μm range (this means approximately > 100 µm) is to be covered during
sampling, significantly larger volumes of water shall be filtered (several litres to over several cubic
meters). Very large representative sample volumes are necessary to be taken in the almost solids-free
ISO 24187:2023(E)
water body. Depending on the detection method, however, the sample volumes may differ. Especially in
the small and very small particle range (this means approximately < 10 µm), microscopic-spectroscopic
methods manage with smaller amounts of water. For macroplastics, other sample volumes shall be
determined or otherwise specified in such a way that a representative sample can be taken.
7.3 Mesh sizes
For all water filtration processes, it is recommended to use the particle size classes shown in Table 1, so
that results can be evaluated according to the size classes and for comparison of different investigations.
In the case of high concentrations of solids in water sample and large sample volumes, a fractionated
filtration contributes to reducing filter cake formation and subsequent blockage or partial blockage of
filters.
In the case of filter cartridges or sieve cascades, a verification of the defined pore size or the nominal
mesh size shall be carried out and recorded. Filterability shall be ensured over the entire sampling
period as well as the complete removal of filter residues from previous measurements in case of
repeated use of the materials. For quality assurance regarding the filtration process, recovery tests are
recommended. They are recommended regarding the filter materials (pore sizes) using standardized
procedures (ISO 2942). For sampling particles smaller than 10 μm, pressure or vacuum filtration is
necessary (approximately 20 Pa to 60 Pa) due to the low water permeability of the filters.
The immersion depth and orientation of the sampling container/sampling device opening with respect
to the flow direction (angle to the incident flow) during the sampling process is to be documented.
Ideally, the hydrodynamic conditions should be documented as well (possibility of isokinetic sampling).
When using neuston or plankton nets or cascades (especially for marine water), the same particle
classification described above (see Table 1) should also be used.
Other commonly used sampling methods can be applied, such as sediment traps, membrane filter
systems and flow centrifuges, but have not yet been sufficiently characterized for microplastics
measurements. Therefore, no recommendations are made to date. Furthermore, there are no
recommendations for preferred sampling by means of random samples or aggregate samples. When
using collection containers for continuous sampling, care shall be taken to homogenize the sample
during further processing (biological growth, sedimentation or flotation effects).
In the documentation of sampling methods, the depth from surface during sampling, the sampled water
volume and the effectively filtered water volume shall always be reported.
7.4 Filter materials
The selection of the filter material can be decisive with regard to the research question and the planned
analysis techniques. The filter materials should also be plastics-free. Non-polymer filter materials (e.g.
stainless steel, silica, alumina) have proven to be very helpful.
Check the filter for inorganic or organic contaminants or residues before use.
8 Sampling of terrestrial, semiterrestrial and subhydric soils
8.1 General
All soil sampling standards refer to nutrients or contaminants that are either adsorbed to soil particles
or are probably finely dispersed. The sampling and pre-treatment of terrestrial, semiterrestrial and
subhydric soils as well as solid materials fundamentally require validation tests.
8.2 Sampling of terrestrial soils
In this subclause, first hints for the sampling of terrestrial soils are given. So far, there is not much
experience with microplastics analysis of soils. As with the taking of water samples, the determination
of a representative sample is also the decisive factor here. This depends on the number of particles and
ISO 24187:2023(E)
particle size. As a first step, ISO 18400-203, ISO 18400-205, ISO 23611-2, ISO 23611-3, ISO 23611-4 and
ISO 23611-5 should be followed.
8.3 Sampling of semiterrestrial soils
Semi-terrestrial soils are under the influence of (ground)water and may also be subject to occasional
flooding. However, the flooding periods are irregular and short. This may also include river banks and
beaches by the sea. In principle, the same extraction methods can be used as for terrestrial soils.
8.4 Sampling of subhydric soils (sediments)
Subhydric soils are permanently under water. Depending on the discipline, they are also referred to as
lake sediment or marine sediment. ISO 5667-12 provides guidance on the sampling of unconsolidated
sediments for the determination of their geological, physical and chemical properties, as well as the
determination of biological, microbiological and chemical properties at the water and sediment
interface. Guidance on obtaining sediment cores is given specifically for the measurement of rates of
deposition and detailed strata delineation. The environments considered are:
— limnic (rivers, streams and lakes, natural and man-made);
— estuarine, including harbours;
— marine sediments.
9 Sampling of air
9.1 Indoor air
ISO 16000-34 specifies the general strategies for determining the concentration of airborne particles
indoors and covers the size range from approximately 1 nm to 100 µm. In addition, this document
describes methods for identifying typical indoor particle sources and gives general recommendations
for obtaining a representative sample. The main sources of indoor particulate matter are described in
this document, together with indoor particle dynamics. Various measurement methods are described,
along with their advantages, disadvantages and areas of application, as well as some general sampling
recommendations. Measurement strategies for determining airborne particles indoors are discussed,
including reference case studies with more specific sampling recommendations.
Additional documents in the ISO 16000 series will focus on each fraction of airborne particulate matter
and give specific recommendations for these measurements.
9.2 Outdoor air
The ambient air quality at a particular location or region is generally variable with time, this variation
being caused by a number of factors, especially meteorological conditions, topography and patterns of
emissions. Such circumstances may require that a large number of measurements be made over a long
interval of time to ensure that a sufficiently wide range of conditions is covered. Stratified sampling is
one method which reduces the number of measurements needed to assess certain aspects of ambient
air quality. This technique has been applied for example in ambient air quality surveys and in noise
[38]
surveys .
ISO 9359 specifies a method for the assessment of certain aspects of ambient air quality in terms of
percentiles and means using the principle of stratified sampling.
10 Sampling of sludges and other similar materials
Similar to the water and soil, the preliminary work in the relevant ISO committees shall also be taken
into account when investigating sewage sludge. However, as already mentioned above, previous
ISO 24187:2023(E)
experience with sampling cannot be easily transferred to the field of plastics. The size and number of
plastics particles, in particular, play an important role in representative sampling. However, ISO 5667-13
should be mentioned here in any case.
In addition to the standards from ISO/TC 147 “Water quality”, standards from ISO/TC 134 “Fertilizers,
soil conditioners and beneficial substances” or ISO/TC 275 “Sludge recovery, recycling, treatment and
disposal” can also contain helpful information.
Fertilizers are commercial products and are available in various types of packaging. Sampling is often
carried out on heaps. ISO/TR 5307 gives first indications. From ISO 7410, ISO/TR 7553, ISO 7742 and
ISO 3963, further information about what has to be considered for such sampling can be obtained.
11 Sampling of mineral and other inorganic materials
ISO 14488 specifies methods
...