prEN ISO 16094-3

Water quality - Analysis of microplastic in water - Part 3: Thermo-analytical methods for waters with low content of suspended solids including drinking water (ISO/DIS 16094-3:2024)

This document sets out key principles for the investigation of microplastics using thermo-analytical methods in water with low content of natural suspended solids.
This document gives requirements for the standardisation of methods towards harmonized procedures for determination of microplastics contents.

Wasserbeschaffenheit - Analyse von Kunststoffen in Wasser - Teil 3: Thermo-analytisches Verfahren für Wasser mit geringen Gehalten an natürlichen Schwebstoffen (ISO/DIS 16094‑3:2024)

Qualité de l'eau - Analyse des microplastiques dans l'eau - Partie 3: Méthodes thermo-analytiques pour les eaux à faible teneur en matières en suspension, y compris l'eau potable (ISO/DIS 16094-3:2024)

Kakovost vode - Analiza mikroplastike v vodi - 3. del: Metode termične analize za vodo z nizko vsebnostjo suspendiranih trdnih delcev, vključno s pitno vodo (ISO/DIS 16094-3:2024)

General Information

• Status: Not Published
• Publication Date: 13-Jan-2026
• ICS: 13.060.45 - Examination of water in general
• Technical Committee: CEN/TC 230 - Water analysis
• Drafting Committee: CEN/TC 230 - Water analysis
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 13-Sep-2024
• Due Date: 11-Jan-2024
• Completion Date: 13-Sep-2024
• Ref Project: oSIST prEN ISO 16094-3:2024 - Water quality - Analysis of microplastic in water - Part 3: Thermo-analytical methods for waters with low content of suspended solids including drinking water (ISO/DIS 16094-3:2024)

Overview

prEN ISO 16094-3 / ISO/DIS 16094-3:2024 - "Water quality - Analysis of microplastic in water - Part 3: Thermo-analytical methods for waters with low content of suspended solids including drinking water" sets out harmonized principles and requirements for the thermo-analytical analysis of microplastics in waters with low total suspended solids (TSS), including drinking water. It focuses on polymer identification and mass quantification using thermal techniques and is intended to improve comparability and reliability of microplastic data for environmental and health assessments.

Key topics and requirements

• Scope and limitations
  • Applicable to waters with low natural TSS (including drinking water); not intended for particle size, shape or number determinations.
  • Describes detection of major polymer types (PE, PP, PET, PS) and additional polymers where detectable (e.g., PVC, PC, PMMA, PA, PU).
• Thermo‑analytical techniques covered
  • Thermal Extraction Desorption - Gas Chromatography - Mass Spectrometry (TED‑GC‑MS) for water filtrate residues.
  • Pyrolysis - Gas Chromatography - Mass Spectrometry (Py‑GC‑MS) for filtrate residues and isolated particles.
  • Guidance on identification and mass‑based quantification workflows for each method.
• Sample handling and preparation
  • Standardized steps for filtration, drying, and homogenisation of filtration residues prior to thermo‑analysis.
  • Cleaning protocols and laboratory environment precautions to minimise contamination.
• Quality assurance and control
  • Requirements for QA/QC measures, use of plastic reference materials, and procedures to determine limits of detection (LOD) and quantification (LOQ). The standard provides exemplary LOD/LOQ guidance (e.g., absolute minimum detectable masses in the µg range depending on method).
• Reporting
  • Recommended content of the test report to support transparent data interpretation and comparability.

Applications and users

• Environmental and municipal water quality monitoring programs assessing microplastic contamination in drinking water and low‑TSS surface/ground waters.
• Accredited analytical laboratories implementing harmonized thermo‑analytical methods (TED‑GC‑MS, Py‑GC‑MS) for polymer identification and mass quantification.
• Regulators and public health agencies establishing monitoring frameworks or reference methods for microplastics in potable water.
• Research groups studying microplastic sources, fate and exposure where mass‑based polymer identification is required.

Related standards

• ISO 24187 - Principles for the analysis of microplastics present in the environment
• ISO 472, ISO 1043 - Plastics vocabulary and polymer symbols
• ISO 11358 - Thermogravimetry of polymers
• ISO 14644‑1 - Cleanrooms and controlled environments
• ISO 17034 - Reference materials guidance

This standard supports consistent, reproducible microplastic analysis using thermo‑analytical methods and helps stakeholders generate comparable data for risk assessment, regulation and water safety decisions.

Standards Content (Sample)

SLOVENSKI STANDARD
01-september-2024
Kakovost vode - Analiza mikroplastike v vodi - 3. del: Metode termične analize za
vodo z nizko vsebnostjo suspendiranih trdnih delcev, vključno s pitno vodo
(ISO/DIS 16094-3:2024)
Water quality - Analysis of microplastic in water - Part 3: Thermo-analytical methods for
waters with low content of suspended solids including drinking water (ISO/DIS 16094-
3:2024)
Wasserbeschaffenheit - Analyse von Kunststoffen in Wasser - Teil 3: Thermo-
analytisches Verfahren für Wasser mit geringen Gehalten an natürlichen Schwebstoffen
(ISO/DIS 16094-3:2024)
Qualité de l'eau - Analyse des microplastiques dans l'eau - Partie 3: Méthodes thermo-
analytiques pour les eaux à faible teneur en matières en suspension, y compris l'eau
potable (ISO/DIS 16094-3:2024)
Ta slovenski standard je istoveten z: prEN ISO 16094-3
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.

DRAFT
International
Standard
ISO/DIS 16094-3
ISO/TC 147/SC 2
Water quality — Analysis of
Secretariat: DIN
microplastic in water —
Voting begins on:
Part 3: 2024-06-21
Thermo-analytical methods
Voting terminates on:
2024-09-13
for waters with low content
of suspended solids including
drinking water
ICS: 13.060.45
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
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Reference number
ISO/DIS 16094-3:2024(en)
DRAFT
ISO/DIS 16094-3:2024(en)
International
Standard
ISO/DIS 16094-3
ISO/TC 147/SC 2
Water quality — Analysis of
Secretariat: DIN
microplastic in water —
Voting begins on:
Part 3:
Thermo-analytical methods
Voting terminates on:
for waters with low content
of suspended solids including
drinking water
ICS: 13.060.45
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2024
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland Reference number
ISO/DIS 16094-3:2024(en)
ii
ISO/DIS 16094-3:2024(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols and abbreviated terms. 3
5 Principle . 3
6 Materials . 4
6.1 Reagents/Consumables .4
6.2 Plastic reference material .4
7 Precautions for laboratory environment, apparatus and materials . 5
7.1 Operating precautions for laboratory environment .5
7.2 Cleaning protocol for materials and equipment .5
8 Sample preparation: handling of samples before analysis . 6
8.1 Filtration .6
8.2 Drying of filtration residues .6
8.3 Homogenisation of filtration residues .6
9 Procedure . 7
9.1 General .7
9.2 Investigations of filtration residues from water using TED-GC-MS (Method 1) .7
9.2.1 Procedure .7
9.2.2 Identification .7
9.2.3 Quantification .8
9.2.4 Quality assessment and control .9
9.3 Investigations of filtration residues from water using Py-GC-MS (Method 2) .10
9.3.1 Procedure .10
9.3.2 Identification .11
9.3.3 Quantification . 12
9.3.4 Quality assessment and control . 13
9.4 Investigation of isolated particles using Py-GC-MS (Method 3) . 13
9.4.1 Procedure . 13
9.4.2 Identification .14
9.4.3 Quantification .14
9.4.4 Quality assessment and control .14
10 Test report .15
Annex A (informative) Exemplary LOD/LOQ values .16
Bibliography .18

iii
ISO/DIS 16094-3:2024(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.
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.

iv
ISO/DIS 16094-3:2024(en)
Introduction
Pollution linked to microplastics is recognised as a global phenomenon. The standardisation 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 summarises the characteristics and the information
obtained with the thermo-analytical technics.
Table 1 — Characteristics of the various analytical techniques and information obtained
Thermal Extraction Desorption
Pyrolysis associated with Gas Chromatog-
associated with Gas Chromatography
raphy - Mass Spectrometry
- Mass Spectrometry
Type of Sample Water filtrate residue Isolated particles
Chemical nature of the
Yes
polymer
Information provided by
Thermal decomposition products
analytical technique
Results expression Polymer type, mass Polymer type
Minimum measurable size
Undefined Visual identify-cation
of particles
Minimum mass subject to
0,1 – 2 µg 0,01 – 1 µg
measurement after prepa-
(absolute) (absolute)
ration
v
DRAFT International Standard ISO/DIS 16094-3:2024(en)
Water quality — Analysis of microplastic in water —
Part 3:
Thermo-analytical 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 provides key principles for the analysis of microplastics in drinking water and water with
low content of natural suspended solids using thermo-analytical methods.
This document is applicable for the determination of types of polymers and mass of microplastics in the sample.
This document is not applicable for the determination of particle size, particle shape and particle numbers.
This document is applicable for the detection of microplastics in drinking water and waters with low content
1)
of natural total suspended solids (TSS) .
NOTE However, the described detection procedures can also be applied to other sorts of samples. Whenever
a laboratory applies this standard for detection of microplastics in water with higher contents of TSS than defined
here, additional quality assessment and control (including preparation) is recommended to be applied to verify that
detection methods are also appliccable for higher amounts of TSS.
This standard describes the detection of different sort of polymers, which are the main ones (most used in
industry and most abundant in the environment) being: polyethylene (PE), polypropylene (PP), polyethylene
terephthalate (PET), and polystyrene (PS). These types of polymers can be analysed by all thermo-analytical
methods. Depending on the used thermo-analytic methods, additional further polymer can be detected,
such as polyvinylchloride (PVC), polycarbonate (PC), poly-methylmethacrylate (PMMA) polyamides (PA),
2)
polyurethanes (PU) and as well as signals from PS-co-polymers .
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 472:2013, Plastics — Vocabulary
ISO 1043-1, Plastics — Symbols and abbreviated terms — Part 1: Basic polymers and their special characteristics
ISO 4880:1997, Burning behaviour of textiles and textile products — Vocabulary
1) ISO 6107 (1-100 mg/l) or lower if they interfere with determination; in future a reference to ISO 5667-27 is desirable,
which is still under development.
2) Signals from PS-co-polymers can be derivate from tire wear and can be detect with the methods as well, but elastomers
are outside the scope of this document.

ISO/DIS 16094-3:2024(en)
ISO 8421-1:1987, Fire protection — Vocabulary — Part 1: General terms and phenomena of fire
ISO 11074:2015, Soil quality — Vocabulary
ISO 11358, Plastics — Thermogravimetry (TG) of polymers — General principles
ISO 14644-1, Cleanrooms and associated controlled environments — Part 1: Classification of air cleanliness by
particle concentration
ISO 17034 GUIDE-30:33, 35, Reference materials — Guidance for characterization and assessment of
homogeneity and stability
ISO 24187, Principles for the analysis of microplastics present in the environment
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
microplastic
any 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 show 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.
3.2
thermal analysis
group of techniques in which a physical property of a substance is measured as a function of temperature or
time while the substance is subjected to a controlled temperature program
Note 1 to entry: The adjective corresponding to “thermal analysis” is “thermo-analytical” (as in, for example, thermo-
analytical techniques).
Note 2 to entry: When two or more techniques are applied to the same test sample at the same time, they should
be identified as “simultaneous multiple techniques”, for example simultaneous thermogravimetry and differential
thermal analysis. The term “combined multiple techniques” would indicate the use of separate test samples for each
technique.
[SOURCE: ISO 472:2013, 2.1160]
3.3
pyrolysis
irreversible chemical decomposition of a material due to an increase in temperature without oxidation
[SOURCE: ISO 8421-1:1987, 1.44; ISO 4880:1997, 53; ISO 11074:2015, 6.4.33]

ISO/DIS 16094-3:2024(en)
3.4
degradation
irreversible process leading to a significant change in the structure of a material, typically characterised
by a change of properties (e.g. integrity, molecular mass or structure, mechanical strength) and/or by
fragmentation, affected by environmental conditions, proceeding over a period of time and comprising one
or more steps
[SOURCE: ISO 472:2013, 2.262]
3.5
thermal decomposition
process whereby the action of heat or elevated temperature on an item causes changes in the chemical
composition
Note 1 to entry: “thermal decomposition” is not the same as “thermal degradation”.
[SOURCE: ISO 472:2013, 2.1285]
4 Symbols and abbreviated terms
Table 2 — Polymers/polymeric materials
ABS acrylonitrile butadiene styrene
CM calibration material
GC-MS gas chromatography – mass spectrometry
GFF glass fibres filters
LOD limit of detection
LOQ limit of quantification
ISTD internal standard
m/z mass-to-change ratio
PA polyamide (polymer of caprolactam = PA6, polymer of hexamethylenediamine and adipic acid =
PA 66)
PC polycarbonate
PE polyethylene
PET poly(ethylene terephthalate)
PMMA poly(methyl methacrylate)
PP polypropylene
PS polystyrene
PTFE polytetrafluoroethylene
PUR -MDI polyurethane, based on methylene diphenyl diisocyanate
PVC poly(vinyl chloride)
Py-GC-MS pyrolysis-gas chromatography – mass spectrometry
SBR styrene butadiene polymer
S/N signal-to-noise ratio
TED-GC-MS thermo extraction desorption-gas chromatography – mass spectrometry
TMAH tetramethylammonium hydroxide
TPU-MDI thermoplastic polyurethane, based on methylene diphenyl diisocyanate
5 Principle
All thermo-analytical techniques described in this document consist of different steps: pyrolysis, transfer/
separation and detection/quantification. In a first step, the samples are heated up in an inert atmosphere

ISO/DIS 16094-3:2024(en)
until decomposition (pyrolysis). In a second step, the resulting decomposition products are either directly
separated on a GC column (pyrolysis GC-MS) or first selectively adsorbed/desorbed on a solid-phase material
before they are introduced into the chromatographic system (TED-GC-MS). In a third step, polymer-specific
decomposition products are detected and quantified (detection/quantification). The various techniques
available differ in how these three steps are realised.
This document encompasses thermo-analytical techniques using gas chromatography/mass spectrometry
(GC-MS) as separation and detection/quantification step. For microplastics detection, there are mainly two
GC-MS-based techniques available:
— thermal extraction and desorption gas chromatography/mass spectrometry (TED-GC-MS).
— pyrolysis gas chromatography/mass spectrometry (Py-GC-MS).
In TED-GC-MS, a sample is heated up in a thermobalance (see ISO 11358) under a continuous nitrogen gas flow.
At the outlet of the oven, a solid phase sorbent is located, collecting a part of the decomposition products of
the sample. After this process the solid phase sorbent is transferred to a thermal desorption unit, in which
the collected decomposition products are remobilised, trapped, re-focused and then transferred to the GC-MS
system. A relatively large sample mass of filtration residues (5 mg to 100 mg) can be analysed with TED-GC-MS.
In Py-GC-MS a sample is thermally decomposed at defined temperatures and under inert conditions. The
volatile decomposition products are transferred via a high temperature split injector into a GC-MS system
with optional cryo-trapping.
Using Py-GC-MS, only lower sample masses of filtration residues (< 1 mg) can be analysed. Therefore, when
Py-GC-MS is applied, the investigated volume should be adjusted accordingly. Depending on the load of
organic accompanying matrix, an additional sample preparation step can be analytically useful. However,
in case of water samples with very low natural organic solids, no additional sample preparation is needed.
The total mass of microplastic particles captured on filters shall be related to the total sample mass (i.e.
µg/g), when reporting the microplastic content as a mass fraction. In case of water filtrate samples, the
analysed (i.e. filtrated) volume can be used to express the microplastics concentration in terms of mass per
volume (i.e. µg/l).
More detailed descriptions of the techniques and measurement parameters are provided in Clause 9.
6 Materials
6.1 Reagents/Consumables
Filter materials with appropriate pore size according to microplastic definition shall be made of inorganic
material (glass fibres, alumina). When the filter is used for prefiltration also organic materials are possible
(cellulose).
As possible cleaning or purge detergent the following solutions exists:
— Ultrapure water previously filtered using a filter (<1 µm pore size filters made of inorganic materials);
— Ethanol (a volume fraction of 10 % to 70 %) with water in the above described quality;
— pharmaceutical quality water / water for injections (water for the preparation of medicines for parenteral
administration when water is used as a vehicle and for dissolving or diluting substances or preparations
for parenteral administration.
6.2 Plastic reference material
For all thermo-analytical methods, polymers (pure reference materials, solved polymers or polymer
powders with inorganic diluents) and ideally without significant amounts of additives or fillers are suitable
as reference material (here named as calibration material, CM). Since thermo-analytical methods do not
measure particle size, generally CM can be used in any form. However, homogeneous polymer powders (<

ISO/DIS 16094-3:2024(en)
100 µm) that are easy to dose are particularly suitable and prevent size related effects on heat transfer. In
some cases, aged polymers particles can be easier to handle (static charge, cryogenic grinding).
However, dealing with environmental samples with a wide variety of possible and unknown polymer
sources, the same decomposition products from one analytical sample can originate from different types
of polymers (e.g. copolymers, polymer blends) and this type cannot be identified by further signals or
additional sample preparation steps. In these cases, the results can be used for identification and clustering
purposes. Quantification can only be related to the respective, defined basic pure polymer.
7 Precautions for laboratory environment, apparatus and materials
7.1 Operating precautions for laboratory environment
Since plastic is ubiquitous, the determination of identically procedural and instrument blank values is of
decisive importance in addition to the examination of the environmental samples to correct the analysis
results for possible foreign or secondary contamination. Especially in the case of very low plastic particle
contamination, the blank values are decisive for the quality and significance of the analysis.
It is recommended, that the space dedicated to the preparation of samples shall be plastic-free or the
amount of plastic should be kept to a minimum (e.g. wall fabrics, flooring). Regular cleaning of the working
environment is essential (for example hood, bench), suitable detergent or wipes (that do not destroy or
degrade the laboratory working conditions or contaminate by further particles) shall be used. Ideally, the
work will be done in laminar flow hood e.g. ISO 14644-1.
In particular, operators shall
— wash hands (including gloves) before initiating the measurement procedure and at each critical step
thereof, particularly after the external washing of the containers and when entering the premises
dedicated to handling samples.
— wear a cotton laboratory coat or, if applicable, a clean antistatic laboratory coat, 100 % cotton textiles
shall be used.
— when possible, avoid wearing protective polypropylene face masks.
— avoid wearing clothing made of synthetic fibres (e.g. fleece jackets, scarfs), personal hygiene or cosmetic
products (e.g. abrasion of nail polish, presence of microplastics in foundations) liable to release
microplastics in the work environment.
— ensure that any equipment or part of the body placed inside the laminar flow hood has undergone a
decontamination step.
The laboratory shall ensure that the sample is protected from any contamination due to the working
environment, particularly during the transport of the sample between the sample preparation and the
detection station.
7.2 Cleaning protocol for materials and equipment
The use of plastic laboratory equipment in contact with the sample should be kept to a minimum. This
includes containers and covers for sample storage, tubes for filtrations, filter holders or sealings. Where
possible materials made of glass or metal shall be used
Special care shall be taken not to contaminate glassware and metal items in contact with samples, including
sample containers, vessels for pyrolysis experiments (i.e. crucibles, vials, quartz tubes or cups).
The following procedures or steps shall be applied to those materials:
— Immerse the glass elements in a suitable detergent solution with sufficient contact time (e.g. 12 h). Then
rinse the elements with an appropriate product (e.g. 70 % ethanol) and finish the rinsing with water
filtrated using a filter made of inorganic materials with a pore size smaller than 1 µm.

ISO/DIS 16094-3:2024(en)
— Utensils containers shall be calcined in the oven at a minimum of 480 °C for 2 h or 450 °C for 6 h. This
includes glass fibre filters (GFF).
— Quartz wool, used in particular to maintain samples in pyrolysis supports, shall be conditioned
beforehand at a minimum temperature of 500 °C for at least 2 h. Unless the wool is guaranteed to be
plastic free, this shall serve to minimise plastic contamination in the particularly critical pyrolysis unit.
— A possibility is also the treatment with open flame (Bunsen burner or similar) for 10 seconds as a cleaning
protocol, especially when using tweezers in direct contact with microplastics.
— After cleaning, glassware and metal parts shall be stored in glass or metal containers or under a laminar
flow hood. Contamination of particles can be minimised by storing glassware with aluminum foil or in
glass Petri dishes.
8 Sample preparation: handling of samples before analysis
8.1 Filtration
This clause describes sample preparation steps of thermo-analytical methods which are mandatory for the
detection of microplastics in drinking water and water with low suspended solids to avoid interferences.
The analysis of water samples usually includes a filtration step to separate solid matter (particles) from the
water. The conditions of filtration, including relevant mesh sizes are defined in ISO 16094-1. Alternatively,
a selection of individual particles can be done by eye or under an optical microscope, using tweezers, which
then are analysed individually.
8.2 Drying of filtration residues
Thermo-analytical methods analyse solid samples, this means, that in case of microplastic analysis of water,
a water filtration residue using a meaningful sampling tool is analysed. Therefore, it is advisable to first
dry the sample to determine a dry weight. Drying is also advantageous to avoid biological growth during
longer storage. The drying process shall continue until the weight of the sample is constant. The duration
until the weight is constant (measured under room conditions at 20 °C, 1,013 bar, e.g. ISO 1) depends on
the source of the sample, the chemical composition and the temperature which is applied. Drying shall be
carried out at room temperature up to a maximum of 40 °C, a temperature over 60 °C should be avoided,
since above this temperature window conventional plastic types (PE, PP, PS, PET, PA, PVC) exhibit specific
phase transitions (glass transition temperature, melting temperature) that are associated with altered
decomposition mechanisms. With respect to larger amounts of sample material, the use of freeze drying
helps to avoid agglomeration.
Samples or filters with samples shall be weighed using a suitable balance (i.e. analytical balance capable of
weight measurements down to 0,1 mg, accuracy 0,01 mg or better).
If during sample preparation the sample is turned into a very dry, powdery item, the effect of static charge
can become a problem, which can lead to the loss of microplastic particles. It shall be decided on a case-
by-case basis whether appropriate wetting with moisture or solvents or the use of appropriate anti-static
devices reduces the problem in the handling of samples.
8.3 Homogenisation of filtration residues
The preparation of the dry field sample to a laboratory sample can initially include sufficient homogenisation
of the sample. Because thermo-analytical methods do not detect the particle size distribution an additional
fragmentation during this step does not affect the result.
When cryogenic milling is performed, the following rules shall be considered:
— Inspection of the cell gasket: it is essential to check the condition of the gasket. If it is damaged, there is
a risk of losing a fraction of the sample during grinding.

ISO/DIS 16094-3:2024(en)
— Inspection of the cell gasket post-cryogenic milling to determine if small pieces of plastic material can
have been trapped in seams or sides of cell gasket during milling process.
— Heating of the cell before opening. The cell can be placed for 1 h in an oven at 50 °C. The cell may not be
opened if it is still at temperature below room temperature, as condensation phenomena can appear,
bringing moisture into the sample.
— Opening of the cell in a protected area and transfer of the powder into a new glass bottle (calcined
beforehand).
9 Procedure
9.1 General
Depending on the type of sample or the equipment available, there are three thermo-analytical approaches:
— Method 1: Investigation of solid filtration residues from water using gas chromatography-mass
spectrometry with thermal extraction and desorption (TED-GC-MS).
— Method 2: Investigation of solid filtration residues from water using pyrolysis gas chromatography-
mass spectrometry (Py-GC-MS).
Alternatively, a selection of individual particles can be identified by eye or under an optical microscope,
using tweezers and directly analysed individually and thermally decomposed under inert conditions in
Py-GC-MS. In this case also an additional analysis of mass (weighing) and morphology or size (imaging) is
possible, but outside the scope of this document. The analysis of individual particles is also possible using
TED-GC-MS.
— Method 3: Investigation of individual, isolated particles using pyrolysis gas chromatography-mass
spectrometry (Py-GC-MS).
Using different thermo-analytic methods, the detection of different sort of polymers varied: PE, PP, PS, PET
can be analysed with all methods. Depending on the specific thermo-analytic methods used, additional
further polymer can be detected, such as PVC, PC, PMMA, different sorts of PA, PU and PS-co-polymers.
9.2 Investigations of filtration residues from water using TED-GC-MS (Method 1)
9.2.1 Procedure
Solid samples from sampling (using i.e. fractionated filtration, passive sampling, flow centrifuge) can be
used as powder as received. A drying and homogenisation of the samples is recommended. For water with
low content of natural suspend solids no additional sample preparation is needed.
Solid samples of approximately 5 mg to 100 mg are weighed into the pyrolysis vessels. The exact mass amount
depends on the sample composition (organic/inorganic content) and the expected microplastics content in
the sample. Alternatively, small filters in the geometry of a pyrolysis vessels with filtration residues from
water can be used directly in agreement with the technical capabilities of the analytical equipment.
As internal standard (ISTD) 13C labelled or deuterated polymers can be used. For example, 4 µl of dissolved
deuterated polystyrene (fivefold deuterated aromatic ring) is added to each pyrolysis vessel (1 mg to 2,5 mg/
ml toluene). It shall be ensured that the pyrolysis vessel does not exhibit any leakage.
9.2.2 Identification
Examples of polymer decomposition products and marker ions and marker fragment ions are summarised
in Table 3. A recommendation is given for the qualifier (printed in bold). Deviations can also occur when
microplastics are strongly aged or an interaction during decomposition with matrix take place. Therefore,
additionally mentioned decomposition products (thin lines) and their marker fragment ions can be
considered for the validity and plausibility of the result.

ISO/DIS 16094-3:2024(en)
Table 3 — Examples of detectable polymers, polymer decomposition products, marker fragment
ions using TED-GC-MS of solid water residues
Marker ion (quali-
Specific marker fragment
Polymer Polymer decomposition products fier) for quantifica-
ions for identification
tion
m/z m/z
1,11-dodecadiene 81, 55, 95, 109
1,12-tridecadiene 81, 55, 95, 109
PE 1,13-tetradecadiene 81, 55, 95, 109
1,14-pentadecadiene 81, 55, 95, 109 81
1,15-hexadecadiene 81, 55, 95, 109
2,4-dimethylhept-1-ene 70, 98, 82, 126
2,4,6-trimethylnon-1-ene 69, 168, 111, 125
2,4,6-trimethylnon-1-ene 69, 168, 111, 125
PP
2,4,6,8-tetramethylundec-10-ene 111, 69, 154, 210 111
2,4,6,8-tetramethylundec-10-ene 111, 69, 154, 210
2,4,6,8-tetramethylundec-10-ene 111, 69, 154, 210
styrene 104, 78, 51
PS 2,4-diphenyl-1-butene 91, 130, 104, 208 91
2,4,6-triphenyl-1-hexene 91, 117, 207, 194
2-phenylcyclohexene 104, 158, 129, 115 104
SBR
1-phenyl-3,4-divinylcyclohexane /
91, 104, 156, 212
phenyl-[4.4.0]bicyclodecene
vinyl benzoate 105, 77, 51
PET ethyl benzoate 105, 77, 122, 150 105
divinyl terephthalate 175, 104, 132, 147
9.2.3 Quantification
The identified peak areas are normalised for the sample mass and for the peak area of a specific
decomposition product of the internal standard.
CM shall be available for quantification.
Various methods can be used for determining the mass fraction in the samples. The selection of the different
methods leads to slightly different results (influence of the matrix) and is chosen depending on the number
of samples to be analysed, and the available amount of sample mass. The various methods of quantification
measurements shall be repeated at least twice.
Response factors
Based on measurements of defined contents of CM and their signal intensity, the polymer content in the
analysis sample (S) can be determined. For this certain amounts ( m ) of CM are measured and the peak
areas (A1) of decomposition product compared to those of the sample (As). The mass m of polymer in the
S
original sample aliquot is then calculated according to Formula (1):
A
S
mm=⋅ (1)
S 1
A
For the quantification using response factors, the measurements of CM shall be repeated three times. The
sample only needs to be measured once, twice is recommended.
In this way, high number of samples with limited individual sample mass can be analysed, but influence of
the matrix on the analytical result is not considered. Errors can arise from matrix interference.

ISO/DIS 16094-3:2024(en)
Standard addition
After identifying relevant markers in an analysis sample (S), defined contents of CM are added in a second
measurement and the signal intensity in the original sample is related to the mass fraction in the spiked
sample. For this, sample aliquots are spiked with a certain amount ( m ) of CM, measured again and the peak
areas ( A ) of decomposition product compared to those of the unspiked sample aliquots (A ). The mass
1 S
m of polymer in the original sample aliquot is then calculated according to Formula (2):
S
A
S
mm=⋅ (2)
S 1
AA−
1 S
For the quantification using standard addition, the neat sample and the spiked sample needs to be measured
once, twice is recommended.
In this way, a low number of samples can be analysed and a sufficient amount of sample is needed for each.
However, due to the inclusion of the matrix, a result with high analytical accuracy can be expected.
Matrix related response factors
For a set of samples (S1, S2, S3, etc.) with similar matrix composition, a solid compromise between measuring
effort and result accuracy can be achieved using the following protocol:
After identification of relevant markers, defined contents of CM are added for a second measurement to a
single sample (S1) of the sample set. For this sample aliquots are spiked with a certain amount ( m ) of CM,
measured again and the peak areas ( A ) of decomposition product compared to those of the unspiked
sample aliquots (A ). The mass m of polymer in the original sample aliquot is then calculated according
S 1 S 1
to Formula (3):
A
S 1
mm=⋅ (3)
S 11
AA−
11S
The determined mass fraction m of the signal A can be related to further samples of this set (S2, S3, etc)
S1 S1
according to Formula (4):
A
S2
mm=⋅ (4)
S21S
A
S1
The selected sample S1 shall have very high homogeneity, be representative for the sample set and be used
in the same amount as in the first measurement. The measurement of the spiked sample shall be performed
shortly after the measurements of the raw samples.
For the quantification using matrix related response factors, the spiked sample (S1) needs to be measured
twice, the sample of the sets (S2, S3, etc.) needs only to be measured once.
In this way, a high number of samples can be analysed and measurements also for samples with limited
amount of masses is realisable (as long as there is enough of at least one sample). Due to the measurement of
at least one (representative) sample, a result with acceptable analytical accuracy can be expected.
For the weighing of CM an ultra-micro balance (readability 0,00 1 mg, repeatability 0,00 25 mg) shall be
used. The amount of added CM depends on the observed signals of samples and should range in the area of
0,01 mg to 0,4 mg. If possible, solved polymers in dilution series can be used as an alternative.
9.2.4 Quality assessment and control
Instrument blank determination of the complete systems shall be carried out before each measurement.
This includes the measurement with an empty pyrolysis vessel, a clean solid phase sorbent and complete GC-
MS run. If it is not the case, peak areas of detected polymers in blanks were subtracted from sample polymer
signals.
ISO/DIS 16094-3:2024(en)
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