SIST EN ISO 16094-2:2025

Water quality - Analysis of microplastic in water - Part 2: Vibrational spectroscopy methods for waters with low content of suspended solids including drinking water (ISO 16094-2:2025)

This document establishes key principles for the investigation of microplastics in drinking water and water with low content of natural suspended solids using a microscopy technique coupled with vibrational spectroscopy.
This method is applicable to:
—    determine the size of microplastics [which range from 1 µm to 5 000 µm], count them and classify them by size range;
—    identify the chemical composition of microplastics, the main ones (most used in industry and most abundant in the environment) being: polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polycarbonate (PC), polystyrene (PS), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyamide (PA), polymethyl methacrylate (PMMA) and polyurethane (PU);
This method is applicable to water with a low content of organic matter and other suspended matter as defined in ISO 6107 (1 mg/l to 100 mg/l or lower when interfering with the determination), i.e.,
—    ultrapure water;
—    water intended for human consumption;
—    raw groundwaters.
Given the very low concentrations of microplastics usually present in these waters, special attention needs to be paid to potential sources of contamination during sample preparation.
This method is intended to determine and characterize large numbers of particles in the sample in automatic mode.
This method can also identify the nature of the other particles that are outside the scope of this document, for example minerals, proteins, cellulose and pigments.
This method does not apply to the characterization of substances intentionally added to or adsorbed on the surface of microplastics. This method does not apply to the determination of the geometric shape of microplastics.

Wasserbeschaffenheit - Analyse von Kunststoff in Wasser - Teil 2: Verfahren mittels Vibrationsspektroskopie (ISO 16094-2:2025)

Dieses Dokument legt wichtige Grundsätze für die Untersuchung von Mikrokunststoffen in Trinkwasser und Wasser mit einem geringen Gehalt an natürlichen Schwebstoffen unter Verwendung eines Mikroskopieverfahrens in Verbindung mit der Schwingungsspektroskopie fest.
Dieses Verfahren ist anwendbar für:
   die Ermittlung der Größe von Mikrokunststoffen [die von 1 µm bis 5 000 µm reichen], ihre Zählung sowie die Klassifizierung nach Größenbereichen;
   die Bestimmung der chemischen Zusammensetzung von Mikrokunststoffen, wobei die wichtigsten (in der Industrie am meisten verwendeten und in der Umwelt am häufigsten vorkommenden) Mikrokunststoffe Polyethylen (PE), Polypropylen (PP), Polyethylenterephthalat (PET), Polycarbonat (PC), Polystyrol (PS), Polytetrafluorethylen (PTFE), Polyvinylchlorid (PVC), Polyamid (PA), Polymethylmethacrylat (PMMA) und Polyurethan (PU) sind.
Dieses Verfahren ist anwendbar auf Wasser mit einem geringen Gehalt an organischen Stoffen und anderen Schwebstoffen wie in ISO 6107 definiert (1 100 mg/l oder weniger, falls sie die Ermittlung stören), d. h.,
   Reinstwasser;
   Wasser für den menschlichen Gebrauch;
   rohes Grundwasser.
In Anbetracht der sehr geringen Konzentrationen von Mikrokunststoffen, die in diesen Wässern üblicherweise vorhanden sind, ist es erforderlich, bei der Probenvorbereitung besonders auf mögliche Kontaminationsquellen zu achten.
Dieses Verfahren ist für die Ermittlung und Charakterisierung einer großen Anzahl von Partikeln in der Probe im automatischen Modus vorgesehen.
Mit diesem Verfahren kann auch die Beschaffenheit der sonstigen Partikel, die nicht in den Anwendungsbereich dieses Dokuments fallen, z. B. Mineralien, Proteine, Zellulose und Pigmente, bestimmt werden.
Dieses Verfahren gilt nicht für die Charakterisierung von Stoffen, die absichtlich Mikrokunststoffen zugesetzt oder an deren Oberfläche adsorbiert wurden. Dieses Verfahren gilt nicht für die Ermittlung der geometrischen Form von Mikrokunststoffen.

Qualité de l'eau - Analyse des microplastiques dans l'eau - Partie 2: Méthodes de spectroscopie vibrationnelle pour les eaux à faible teneur en matières en suspension, y compris l'eau potable (ISO 16094-2:2025)

Le présent document établit les principes clés de l'étude des microplastiques dans l'eau potable et les eaux à faible teneur en matières en suspension naturelles à l'aide d'une technique de microscopie couplée à une spectroscopie vibrationnelle.
Cette méthode est applicable pour:
—    déterminer la taille des microplastiques [qui va de 1 µm à 5 000 µm], les dénombrer et les classer par intervalles de tailles;
—    identifier la composition chimique des microplastiques, dont les principaux (les plus utilisés dans l'industrie et les plus présents dans l'environnement) sont les Polyéthylène (PE), Polypropylène (PP), Poly(téréphtalate d'éthylène) (PET), Polycarbonate (PC), Polystyrène (PS), Polytétrafluoroéthylène (PTFE), Polychlorure de vinyle (PVC), Polyamide (PA), Polyméthacrylate de méthyle (PMMA) et Polyuréthane (PU);
Cette méthode est applicable aux eaux à faible teneur en matière organique et en autres matières en suspension comme défini dans l'ISO 6107 (1 mg/l à 100 mg/l ou moins lorsque cela interfère avec la détermination), notamment:
—    les eaux ultra pures;
—    les eaux destinées à la consommation humaine;
—    les eaux souterraines brutes.
Étant donné les très faibles concentrations de microplastiques habituellement présentes dans ces eaux, une attention particulière doit être portée aux possibles sources de contamination lors de la préparation de l'échantillon.
Cette méthode a pour but de déterminer et de caractériser un grand nombre de particules dans l'échantillon en mode automatique.
Cette méthode peut aussi identifier la nature des autres particules qui n'entrent pas dans le domaine d'application du présent document, par exemple les minéraux, les protéines, la cellulose et les pigments.
Cette méthode ne s'applique pas à la caractérisation des substances intentionnellement ajoutées ou adsorbées à la surface des microplastiques. Cette méthode ne s'applique pas à la détermination de la forme géométrique de microplastiques.

Kakovost vode - Analiza mikroplastike v vodi - 2. del: Metode vibracijske spektroskopije za vodo z nizko vsebnostjo suspendiranih delcev, vključno s pitno vodo (ISO 16094-2:2025)

Ta dokument določa ključna načela za ugotavljanje prisotnosti mikroplastike v pitni vodi in vodi z nizko vsebnostjo naravnih suspendiranih delcev z uporabo mikroskopske tehnike v kombinaciji z vibracijsko spektroskopijo. Ta metoda se uporablja za: –   določanje velikosti mikroplastike [v razponu od 1 µm do 5000 µm], njeno štetje in razvrščanje po velikosti; –   določanje kemične sestave mikroplastike, pri čemer so glavne (najpogosteje uporabljene v industriji in najpogostejše v okolju) sestavine: polietilen (PE), polipropilen (PP), polietilen tereftalat (PET), polikarbonat (PC), polistiren (PS), politetrafluoroetilen (PTFE), polivinilklorid (PVC), poliamid (PA), polimetilmetakrilat (PMMA) in poliuretan (PU). Ta metoda se uporablja za vodo z nizko vsebnostjo organskih snovi in​drugih suspendiranih snovi, kot je opredeljeno v standardu ISO 6107 (od 1 mg/l do 100 mg/l ali manj, če vplivajo na določanje), tj. –   ultra čisto vodo; –   vodo, namenjeno za pitje; –   neobdelano podtalnico. Glede na to, da so v teh vodah običajno prisotne zelo nizke koncentracije mikroplastike, je treba med pripravo vzorca posebno pozornost nameniti morebitnim virom onesnaženja. Ta metoda je namenjena določanju in karakterizaciji velikega števila delcev v vzorcu v samodejnem načinu. S to metodo je mogoče določiti tudi vrsto drugih delcev, ki ne spadajo na področje uporabe tega dokumenta (npr. minerali, beljakovine, celuloza in pigmenti). Ta metoda se ne uporablja za karakterizacijo snovi, ki so namerno dodane na površino mikroplastike ali se na njej absorbirajo. Ta metoda se ne uporablja za določanje geometrijske oblike mikroplastike.

General Information

• Status: Published
• Public Enquiry End Date: 02-Feb-2024
• Publication Date: 16-Oct-2025
• ICS: 13.060.45 - Examination of water in general
• Technical Committee: KAV - Water quality
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Oct-2025
• Due Date: 06-Dec-2025
• Completion Date: 17-Oct-2025
• Ref Project: EN ISO 16094-2:2025 - Water quality - Analysis of microplastic in water - Part 2: Vibrational spectroscopy methods for waters with low content of suspended solids including drinking water (ISO 16094-2:2025)

Standards Content (Sample)

SLOVENSKI STANDARD
01-november-2025
Kakovost vode - Analiza mikroplastike v vodi - 2. del: Metode vibracijske
spektroskopije za vodo z nizko vsebnostjo suspendiranih delcev, vključno s pitno
vodo (ISO 16094-2:2025)
Water quality - Analysis of microplastic in water - Part 2: Vibrational spectroscopy
methods for waters with low content of suspended solids including drinking water (ISO
16094-2:2025)
Wasserbeschaffenheit - Analyse von Kunststoff in Wasser - Teil 2: Verfahren mittels
Vibrationsspektroskopie (ISO 16094-2:2025)
Qualité de l'eau - Analyse des microplastiques dans l'eau - Partie 2: Méthodes de
spectroscopie vibrationnelle pour les eaux à faible teneur en matières en suspension, y
compris l'eau potable (ISO 16094-2:2025)
Ta slovenski standard je istoveten z: EN ISO 16094-2:2025
ICS:
13.060.45 Preiskava vode na splošno Examination of water in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 16094-2
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2025
EUROPÄISCHE NORM
ICS 13.060.45
English Version
Water quality - Analysis of microplastic in water - Part 2:
Vibrational spectroscopy methods for waters with low
content of suspended solids including drinking water (ISO
16094-2:2025)
Qualité de l'eau - Analyse des microplastiques dans Wasserbeschaffenheit - Analyse von Kunststoff in
l'eau - Partie 2: Méthodes de spectroscopie Wasser - Teil 2: Verfahren mittels
vibrationnelle pour les eaux à faible teneur en matières Vibrationsspektroskopie (ISO 16094-2:2025)
en suspension, y compris l'eau potable (ISO 16094-
2:2025)
This European Standard was approved by CEN on 14 September 2025.

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
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 16094-2:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 16094-2:2025) has been prepared by Technical Committee ISO/TC 147 "Water
quality" in collaboration with Technical Committee CEN/TC 230 “Water analysis” the secretariat of
which is held by DIN.
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 April 2026, and conflicting national standards shall be
withdrawn at the latest by April 2026.
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 16094-2:2025 has been approved by CEN as EN ISO 16094-2:2025 without any
modification.
International
Standard
ISO 16094-2
First edition
Water quality — Analysis of
2025-09
microplastic in water —
Part 2:
Vibrational spectroscopy methods
for waters with low content
of suspended solids including
drinking water
Qualité de l'eau — Analyse des microplastiques dans l'eau —
Partie 2: Méthodes de spectroscopie vibrationnelle pour les eaux
à faible teneur en matières en suspension, y compris l'eau potable
Reference number
ISO 16094-2:2025(en) © ISO 2025

ISO 16094-2:2025(en)
© ISO 2025
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 16094-2:2025(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 2
3 Terms, definitions and abbreviations . 2
3.1 Terms and definitions .2
3.2 Abbreviations .3
4 Principle . 4
5 Interferences . 4
6 Reagents, consumables and reference materials . 4
6.1 General .4
6.2 Particle-free water of known quality .4
6.3 Surfactant solution .5
6.4 Ethanol .5
6.5 Plastic reference material . .5
6.6 Containers for filter storage .5
7 Precautions for the laboratory environment, equipment and materials . 5
7.1 Operating precautions linked to the laboratory environment .5
7.2 Equipment .5
7.2.1 General .5
7.2.2 Infrared (IR) apparatus coupled to microscope.5
7.2.3 Raman coupled to microscope .6
7.2.4 Filtration system .6
7.2.5 Characteristics of filters: type and sizes.7
7.3 Precautions and cleaning protocol for materials .7
7.4 Bottles or containers for sampling .7
8 Sampling . 8
9 Operating protocol . 8
9.1 Volume of test sample .8
9.2 Sample filtration protocol .8
9.3 Analytical control blanks .9
9.4 Adjustment and calibration of instruments .9
9.4.1 Infrared microscope .9
9.4.2 Raman microscope .9
9.5 Cartesian coordinates of analysed particles.10
9.6 Analysis of the filter surface .10
9.6.1 General .10
9.6.2 Choice of the optical objectives .10
9.6.3 Selection of particles to be analysed or choice of the analysed surface area.10
9.6.4 TOTAL Model .10
9.6.5 RANDOM Model.11
9.6.6 CAKE Model .11
9.6.7 SPIRAL or HELIX Model . 12
9.6.8 Particles enumeration and size description . 12
9.6.9 IR spectra acquisition and particle identification . 12
9.6.10 Raman spectral acquisition and particle identification . 13
9.7 Sampling and analytical control blank analysis . 13
9.8 Spectra treatment . 13
9.9 Criteria of chemical composition identification.14
9.10 Spectral interferences .14
9.10.1 General .14

iii
ISO 16094-2:2025(en)
9.10.2 Pigments or dyes . 15
9.10.3 Polyamide versus natural proteins . 15
9.10.4 Polyethylene versus other molecules with long CH-chain . 15
10 Method characterization and verification .15
10.1 General . 15
10.2 Verification of the particle size measurement accuracy . 15
10.3 Verification of microplastics identification and classification at claimed size . 15
10.4 Determination of minimal HQI for automatic identification .16
10.5 Determination of the reporting limits of the method .16
10.6 Verification of microplastics recovery rate of the method .17
11 Quality check of analytical control blanks in test series . 17
12 Expression of results .18
13 Test report .18
Annex A (informative) List of characteristic wavenumbers for the main polymers .20
Annex B (informative) Creation of an internal spectral database .23
Annex C (informative) Description of known interference during acquisition of spectral
fingerprint — Presence of pigments . .26
Annex D (informative) Description of known interference during acquisition of spectral
fingerprint — Interference between natural and synthetic polyamides (proteins and
polyamide 6-6) .27
Annex E (informative) Description of a known interference during acquisition of a spectral
fingerprint – Interferences of molecules with long CH-chain . .29
Annex F (informative) Quantum Cascade Laser (QCL) IR microscopy .32
Annex G (informative) Performance data .33
Bibliography .35

iv
ISO 16094-2:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had 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 147, Water quality, Subcommittee SC 2, Physical,
chemical and biochemical methods, in collaboration with the European Committee for Standardization
(CEN) Technical Committee CEN/TC 230, Water analysis, in accordance with the Agreement on technical
cooperation between ISO and CEN (Vienna Agreement).
A list of all parts in the ISO 16094 series can be found on the ISO website.
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.

v
ISO 16094-2:2025(en)
Introduction
Pollution linked to microplastics is recognized as a global phenomenon. The standardization of the sampling,
quantification and identification protocols is required to ensure reliability and comparability of the data
produced for health and environmental risk assessments.
Microplastics in water can be identified and quantified using various methodological approaches. Depending
on the measurement objectives, several complementary approaches shall be used to cover the full spectrum
of microplastics (size and chemical nature). Table 1 resumes the characteristics and the information
obtained with spectroscopic techniques.
Table 1 — Characteristics of the various analytical techniques and information obtained.
Characteristics and information ob-
Raman micro spectroscopy Infrared micro spectroscopy
tained
Type of sample Water filtrate residues
Chemical nature of the polymer Yes
Information provided by analytical
Functional groups
technique
Results expression Polymer type, number of particles, size of particles
Minimum measurable size range of
1 µm to 5 µm 20 µm
particles
Minimum mass subject to measure-
Undefined
ment after preparation
Consequences for the test sample after
Non-destructive
measurement
Main interferences mineral particles, coloured par- mineral particles, proteins, surface
ticles, pigments, fluorescence, alterations by biofilms or weathering,
fatty acids, fatty amides, proteins, particles loaded with carbon black,
surface alterations by biofilms or presence of water, carbohydrates gen-
weathering, carbohydrates, gener- erated by microbes
ated by microbes
vi
International Standard ISO 16094-2:2025(en)
Water quality — Analysis of microplastic in water —
Part 2:
Vibrational spectroscopy methods for waters with low
content of suspended solids including drinking water
WARNING — Persons using this document should be familiar with normal laboratory practice. This
document does not purport to address all of the safety problems, if any, associated with its use. It is
the responsibility of the user to establish appropriate safety and health practices.
IMPORTANT — It is absolutely essential that tests conducted in accordance with this document be
carried out by suitably qualified staff.
1 Scope
This document establishes key principles for the investigation of microplastics in drinking water and
water with low content of natural suspended solids using a microscopy technique coupled with vibrational
spectroscopy.
This method is applicable to:
— determine the size of microplastics [which range from 1 µm to 5 000 µm], count them and classify them
by size range;
— identify the chemical composition of microplastics, the main ones (most used in industry and most
abundant in the environment) being: polyethylene (PE), polypropylene (PP), polyethylene terephthalate
(PET), polycarbonate (PC), polystyrene (PS), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC),
polyamide (PA), polymethyl methacrylate (PMMA) and polyurethane (PU);
This method is applicable to water with a low content of organic matter and other suspended matter as
defined in ISO 6107 (1 mg/l to 100 mg/l or lower when interfering with the determination), i.e.,
— ultrapure water;
— water intended for human consumption;
— raw groundwaters.
Given the very low concentrations of microplastics usually present in these waters, special attention needs
to be paid to potential sources of contamination during sample preparation.
This method is intended to determine and characterize large numbers of particles in the sample in
automatic mode.
This method can also identify the nature of the other particles that are outside the scope of this document,
for example minerals, proteins, cellulose and pigments.
This method does not apply to the characterization of substances intentionally added to or adsorbed on
the surface of microplastics. This method does not apply to the determination of the geometric shape of
microplastics.
ISO 16094-2:2025(en)
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 14644-1:2015, Cleanrooms and associated controlled environments — Part 1: Classification of air cleanliness
by particle concentration
ISO/IEC Guide 99:2007, International vocabulary of metrology — Basic and general concepts and associated
terms (VIM)
3 Terms, definitions and abbreviations
3.1 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 https:// www .electropedia .org/
3.1.1
microplastics
solid plastic or synthetic polymer particle insoluble in water with the largest dimension between 1 μm and 5 mm
Note 1 to entry: Microplastics can have various shapes.
Note 2 to entry: This definition encompasses the ISO/TR 21960 definitions of large microplastics and microplastics.
Note 3 to entry: The term “microplastics” covers the sum of several individual microplastic particles.
3.1.2
microparticle
solid particle insoluble in water, with the largest dimension between 1 μm and 5 mm
3.1.3
Raman spectroscopy
spectroscopy in which the Raman effect (3.1.4) is used to investigate molecular energy levels
[SOURCE: ISO 18115-2:2021, 5.129]
3.1.4
Raman effect
emitted radiation, associated with molecules illuminated with monochromatic radiation, characterized by
an energy loss or gain arising from rotational or vibrational excitations
[SOURCE: ISO 18115-2:2021, 5.128]
3.1.5
infrared spectroscopy
analytical chemical technique based on absorption of infrared radiation by chemical moieties (functional
groups) in the specimen, used to identify and quantitate the absorbing chemical moieties
[SOURCE: ISO/TS 14101:2012, 3.3]
3.1.6
particle-free water
water not containing microplastics (3.1.1) or with the lowest possible concentration of microplastics (3.1.1)

ISO 16094-2:2025(en)
3.1.7
Feret diameter
distance between two parallel lines which are tangent to the perimeter of a particle
[SOURCE: ISO 10788:2014, 2.1.4]
3.1.8
maximum Feret diameter
maximum length of an object whatever its orientation
[SOURCE: ISO/TR 945-2:2011, 2.1]
3.1.9
reporting limit
smallest number of objects (microplastics (3.1.1)) that the laboratory can measure reliably by type of polymer
and size class under routine laboratory operating conditions
Note 1 to entry: A different reporting limit can be associated with each filter reading model.
Note 2 to entry: For the determination of the reporting limit see 10.5.
3.1.10
correlation index
hit quality index
HQI
index or spectral correlation coefficient (typically between 0 and 1) or percentage allowing the calculation
of the similarity between two spectral signatures
3.2 Abbreviations
ATR Attenuated total reflection
FTIR Fourier-transform infrared spectroscopy
HEPA filter High-efficiency particulate air filter
HQI Hit quality index
IR Infrared spectroscopy
PA Polyamide
PC Polycarbonate
PE Polyethylene
PET Poly(ethylene terephthalate)
PMMA Poly(methyl methacrylate)
PP Polypropylene
PS Polystyrene
PTFE Polytetrafluoroethylene
PU Polyurethane
PVC Poly(vinyl chloride)
R Reporting limit
L
SDS Sodium dodecyl sulfate
USAF United States Air Force
µFTIR Microscopy coupled with FTIR spectroscopy
µRaman Microscopy coupled with Raman spectroscopy

ISO 16094-2:2025(en)
4 Principle
Counting and identification are based on filtering a specified volume of a water or prepared water sample
through a filtering membrane with a pore size able to retain the microplastics of interest (based on the
microplastics size class claimed to be analysable by the laboratory). The filter is subsequently analysed by
microscopy coupled with at least one of the following two techniques:
a) Infrared spectroscopy is used to characterize the molecular composition and the structure of a
material. It is based on the absorption of infrared radiation by the analysed material. Absorption bands
are obtained, resulting from intramolecular vibrational modes that absorb the infrared radiation of
characteristic wavenumbers, enabling the identification of organic or mineral materials.
b) Raman spectroscopy is used to characterize the molecular composition and the structure of a material.
A beam of monochromatic light is transmitted onto the sample to be studied and the scattered light
is analysed having been collected by a lens sent into the instrument’s detection unit to measure the
intensity of light in the covered wavenumber range.
Both techniques coupled with optical microscopy µFTIR and µRaman can be used to obtain the size
distribution and number of the microplastics and identify the type of polymer.
5 Interferences
One of the main problems is to correctly detect and identify microplastic particles in real samples when
they are mixed with other solid particles naturally present in the matrices of interest (e.g. minerals, natural
organic matter).
Given the very low concentrations of microplastics usually present in these waters, special attention
should be paid to possible sources of external contamination during sampling and sample preparation.
[ ]
Recommendations 2 for avoiding external contamination by microplastics are given in 7.1, 7.3, 7.4, and
Clause 8.
It should be noted that microplastics spectral identification interference can occur with natural present
particles in the water with similar or partially similar spectral information and can lead to false negative or
false positive results in terms of microplastic identification. Some common cases and recommendations for
the content of the spectral database are given in 9.10 and in Annexes B to E.
6 Reagents, consumables and reference materials
6.1 General
Ensure that water and all chemicals are free from microplastics in advance and remove them by filtration
before use (for example, through the cellulose filter or a non-polymeric membrane with a pore size of < 1 µm).
6.2 Particle-free water of known quality
Water not containing microplastics or with the lowest possible concentration of microplastics, estimated by
calculating the mean value and regularly checked via the test of analytical control blanks.
This water can be prepared by the laboratory using ultrapure water previously filtered using a filter made
of inorganic materials (e.g. a < 1 µm filter). This water can also be purchased.

ISO 16094-2:2025(en)
6.3 Surfactant solution
6.4 Ethanol
6.5 Plastic reference material
The reference materials are used to check process and equipment performance in terms of identification of
size and type of microparticles.
6.6 Containers for filter storage
Glass or metal containers should be used.
7 Precautions for the laboratory environment, equipment and materials
7.1 Operating precautions linked to the laboratory environment
The space dedicated to preparing and filtering samples should be free from polymer coatings or materials.
It shall at least include a laminar flow hood as given in ISO 14644-1:2015, ISO 5 type, equipped with a HEPA
filter. Regular cleaning of the laboratory environment is mandatory (e.g. hood and lab bench). To do this,
ethanol, surfactant, particle-free water and suitable wipes free of synthetic polymers may be used.
In particular, operators shall:
— not wear gloves. If gloves are necessary for safety reasons, potential sample contamination by
microplastics and chemicals which can cause spectral interference with microplastics (9.10 and Annex E)
shall be checked in advance;
— wash their hands prior to starting the manipulations with samples, especially after washing the outsides
of containers and when entering rooms dedicated to handling samples;
— wear a cotton lab coat or, if necessary, a clean anti-static lab coat (e.g. coloured and characterized
regarding the materials/polymer in order to exclude the type of polymer from the sample results report);
— not wear face masks made of synthetic polymers; do not wear clothing made of synthetic fibers (fleece
jackets for example), body cleansing products or cosmetics likely to generate microplastics in the
laboratory environment (e.g. nail varnish, foundations, exfoliating products).
The laboratory should protect the sample from all contamination coming from the laboratory working
environment especially when transporting the sample between the preparation workstation and the
analysis workstation (e.g. by covering the sample with aluminium foil or placing it in a suitable container),
and during the final analysis stage.
7.2 Equipment
7.2.1 General
Depending on the instrument suppliers, the recognition of particles, their acquisition and their identification
may be manual or automatic.
7.2.2 Infrared (IR) apparatus coupled to microscope
— an optical microscope with objectives enabling at least 4× magnification and able to work in visible light;
— a high-resolution camera able to display the particles on a computer screen;
— a suitable positioning system, to move the filter under the IR light beam;

ISO 16094-2:2025(en)
(1))
— a calibrated infrared spectrometer, able to record a spectrum in transmission, reflection or ATR mode
-1 -1(2)) -1
in the infrared range, between 4 000 cm and 750 cm , with resolution better than or equal to 8 cm .
The correct operation of the equipment should be regularly checked by analysing a spectral reference;
— software enabling the acquisition of spectra and the correction of filter background noise and their
comparison with a spectral database;
— a spectral database which contains at least several types of spectra of PE, PET, PP, PS, PC, PVC, PMMA,
PTFE, PA, PU, see Annex A, natural materials that are likely to be present in samples (e.g. proteins,
cellulose, see 9.10 and Annex C to Annex E). The laboratory may supplement the database with spectra
recorded in-house, including those obtained from degraded polymers (UV, thermal degradation).
7.2.3 Raman coupled to microscope
— an optical microscope with at least a 5× objective to illuminate the sample and work at least under
"bright field" light; The use of "dark field" light can be useful in certain specific cases depending on the
filter chosen. Generally, at least a 20× lens is used in this case;
— a high-resolution camera able to display the particles on a computer screen;
— a suitable motorized stage, to move the filter under the laser beam;
— a laser in the wavelength ranges of 532 nm (green) or 785 nm (red) with adjustable power (for which the
power and the sample excitation duration can be modified). The use of a 785 nm laser helps to improve
the identification of certain coloured or fluorescent particles;
-1 -1
— a calibrated Raman spectrometer, able to record a spectrum in the range of 4 000 cm to 200 cm , with
-1
resolution lower than or equal to 6 cm . The correct operation of the equipment should be regularly
checked via the measurement of a reference material (e.g. Si). Correct spectral positioning of the
Raman signal and order of intensity should be checked;
— software for spectrum acquisition, fluorescence correction and comparison of spectra with a spectral
database which contains at least spectra of PE, PET, PP, PS, PC, PVC, PMMA, PTFE, PA, PU, see Annex A,
natural materials that are likely to be present in samples (e.g. proteins, cellulose) and pigments (see
9.10, and Annex C to Annex E). The laboratory may supplement the database spectra recorded in-house,
including those obtained from degraded polymers (UV, thermal degradation).
7.2.4 Filtration system
Plastic items in contact with the sample should be completely avoided: use glass and metal items only.
The filtration system can consist of:
— a vacuum pump or equivalent system;
— a filtration support for discharging the filtered water (filtration manifold, conical flask, flask with neck,
etc.), taking care to ascertain and control the chemical composition of any pipes and seals;
— a filter support that is adapted to the diameter or the surface area of the filter;
— a funnel, e.g. made of glass, suitable for the volume to be filtered;
— a glass or metal protection covering the funnel to protect the sample from atmospheric contamination;
and, if necessary:
— a sintered-glass filter;
— a system to retain the assembly (metal retention clip).
1) ATR is mainly used for identification of single particles (e.g. for confirmation).
2) Some alternate technologies use different spectral range (Annex F).

ISO 16094-2:2025(en)
The filtering operation is performed under a laminar flow hood at least. The filtration equipment shall be
cleaned beforehand (see 7.3).
7.2.5 Characteristics of filters: type and sizes
The types of filter used shall meet the following characteristics:
— compatibility with IR and/or Raman measurements: i.e. filters that do not present spectral bands that can
interfere with the target microplastics and that are suitable for the chosen acquisition mode: reflective
(3))
filters for Raman and reflectance FTIR or IR-transparent filters for transmission FTIR .
— flatness: use filters with the best possible flatness such as silicon, alumina filters or metal (commonly
(4))
gold) covered polycarbonate filters . Filter flatness can be enhanced by using special filter holders;
— without any microplastics release or with a release of an unavoidable minimum guaranteeing minimal
(3)
background noise ;
— heat and mechanical resistance (resistance to laser if Raman is used);
— resistance to oxidation;
— suitable porosity (pores diameter and distance between them).
The size of the filters and pores shall suit the quantity of microparticles and their size in the sample.
10 mm × 10 mm square filters or 13 mm or 25 mm diameter round filters are commonly used in laboratories.
The minimum cut-off threshold (size of filter pores) shall be smaller than the minimum microplastics size
class limit claimed by the laboratory.
When choosing the type of filter, the laboratory will check that the distances between pores are large enough
to perform the correct measurement of background spectrum.
7.3 Precautions and cleaning protocol for materials
Small equipment that can release microplastics such as those analysed (e.g. PP, PC, PA, PTFE) should not be used.
All items (glassware, metal etc.) which are in contact with the samples, including containers for sampling,
shall be subject to special attention and shall be cleaned thoroughly, by applying the following protocol or
other suitable cleaning procedures:
— Immerse the glass items in a suitable surfactant solution, with a sufficient contact time.
— Then rinse the items with a suitable product (e.g. 50 % ethanol or a cleaning agent) and complete rinsing
with particle-free water of known quality (6.3). Leave the equipment in the laminar flow bench to air
dry. Do not wipe it dry.
— As an alternative, glass items can be filled with particle-free water of known quality and surfactant
and put in an ultrasonic bath for 5 min. The water is removed, and the entire procedure is repeated an
additional two times.
— Containers, glassware and utensils may be calcined at 480 °C for 2 h or 450 °C for 6 h.
7.4 Bottles or containers for sampling
The containers used for water sampling shall follow the same cleaning protocol (see 7.3) as the small
equipment and shall be verified by analysing a sampling blank (see clause 8) (containers are not needed for
bottled water).
3) Filters such as polycarbonate with no metal coating, polyamide 6-6 (e.g. nylon), PTFE, etc. are normally not compatible.
Some specific kind of coloured PTFE with recognizable spectral fingerprint may be used with Raman instruments.
4) Depending on the type of equipment (autofocus mode), nitrocellulose filters can be used with IR, f
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