ISO/TS 21396:2017

Rubber - Determination of mass concentration of tire and road wear particles (TRWP) in soil and sediments - Pyrolysis-GC/MS method

ISO/TS 21396:2017 specifies a method for the determination of the soil or sediment mass concentration (μg/g) of tyre and road wear particles (TRWP) in environmental samples. ISO/TS 21396:2017 establishes principles for soil or sediment sample collection, the generation of pyrolysis fragments from the sample, and the quantification of the generated polymer fragments. The quantified polymer mass is used to calculate the concentration of TRWP in soil or sediment. These quantities are expressed on a TRWP basis, which includes the mass of tyre tread and mass of road wear encrustations, and can also be expressed on a tyre rubber polymer or tyre tread basis. NOTE Tyre and road wear particles are a discrete mass of elongated particles generated at the frictional interface between the tyre and roadway surface during the service life of a tyre. The particles consist of tyre tread enriched with mineral encrustations from the roadway surface.

Caoutchouc — Détermination de la concentration massique en particules de pneus et d'usure de la route (TWRP) dans le sol et les sédiments — Méthode par pyrolyse-GC/MS

General Information

• Status: Published
• Publication Date: 20-Dec-2017
• ICS: 13.020.40 - Pollution, pollution control and conservation
• ICS: 83.060 - Rubber
• ICS: 83.160.01 - Tyres in general
• Technical Committee: ISO/TC 45 - Rubber and rubber products
• Drafting Committee: ISO/TC 45/WG 16 - Environmental aspects and sustainability
• Current Stage: 9092 - International Standard to be revised
• Start Date: 15-Nov-2023
• Completion Date: 13-Dec-2025

Overview

ISO/TS 21396:2017 - Rubber - Determination of mass concentration of tire and road wear particles (TRWP) in soil and sediments - Pyrolysis‑GC/MS method specifies a laboratory procedure to quantify the mass concentration (µg/g) of tyre and road wear particles (TRWP) in soil and sediment samples. The technique uses pyrolysis followed by gas chromatography/mass spectrometry (pyrolysis‑GC/MS) to generate and quantify polymer dimer fragments that are specific to tyre rubber polymers. Results can be reported on a TRWP, tyre rubber polymer, or tyre tread basis.

Key topics and technical requirements

• Principle: Thermal decomposition of tyre polymers produces characteristic dimeric pyrolysis fragments (NR, SBR, BR dimers) that are separated by GC and identified by MS. Dimer markers provide greater specificity than monomer markers, which can be interfered with by non‑TRWP sources (e.g., styrene from diesel).
• Sample collection & preparation:
  • Field sampling using pre‑cleaned trowels, corers or dredges.
  • Oven drying at 105 °C for 24 h is specified for dry mass determination.
  • Dry sieving/homogenization (nominal sieve opening ~1 mm) to prepare material for pyrolysis.
  • Precision balance requirements (accuracy to 0.01 mg) for mass measurements.
• Analytical method:
  • Addition of a deuterated internal standard to correct for matrix effects, instrument drift and recovery.
  • Preparation of calibration curves from stock solutions and internal standards.
  • Pyrolyser operation at 670 °C for 5 s in a helium atmosphere; high‑purity helium specified for carrier gas.
• Quantification & reporting:
  • Calculation of polymer mass in the sample from dimer peak areas and internal standard calibration.
  • Conversion of polymer mass to TRWP concentration (µg/g), accounting for tyre tread and mineral encrustation fractions.
• Performance: The specification addresses measuring range, method detection limits, repeatability, and test report requirements.

Applications

• Environmental monitoring of TRWP in urban soils, roadside sediments, and aquatic sediments.
• Comparative and trend studies to assess temporal changes in TRWP loads.
• Supporting environmental impact assessments, source apportionment, and mitigation studies for microplastic and tyre wear pollution.
• Research into tyre composition, road abrasion, and fate/transport of TRWP.

Who should use this standard

• Environmental testing laboratories and analytical service providers.
• Academic and government researchers studying microplastics, particulate pollution, or soil/sediment contamination.
• Regulatory agencies, road authorities and consultants performing baseline or monitoring studies.
• Tire manufacturers and material scientists investigating abrasion and wear.

Related standards

• ISO 7270‑1 - Rubber - Analysis by pyrolytic GC methods - Part 1: Identification of polymers (referenced normatively for pyrolysis‑GC identification procedures).

Keywords: ISO/TS 21396:2017, TRWP, tyre and road wear particles, pyrolysis‑GC/MS, soil, sediments, tyre rubber polymer, dimer markers, deuterated internal standard, environmental monitoring.

Standards Content (Sample)

TECHNICAL ISO/TS
SPECIFICATION 21396
First edition
2017-12
Rubber — Determination of mass
concentration of tire and road
wear particles (TRWP) in soil and
sediments — Pyrolysis-GC/MS method
Caoutchouc — Détermination de la concentration massique en
particules de pneus et d'usure de la route (TWRP) dans le sol et les
sédiments — Méthode par pyrolyse-GC/MS
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, 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.
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ii © ISO 2017 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents . 2
6 Apparatus . 3
7 Specimen preparation laboratory . 5
8 Measuring range . 5
9 Limit of detection . 5
10 Procedure. 6
10.1 General . 6
10.2 Sample collection . 6
10.3 Deuterated internal standard preparation . 6
10.4 Calibration curve preparation . 7
10.4.1 Stock solutions . 7
10.4.2 Calibration curves . 7
10.5 Sample preparation . 8
10.5.1 Oven drying . 8
10.5.2 Sieving and homogenization . 8
10.6 Sample measurement . 8
10.6.1 Sample mass . 8
10.6.2 Internal standard addition . 9
10.6.3 Pyrolysis-gas chromatograph/mass spectrometer measurement . 9
11 Analysis . 9
11.1 TRWP detection limit . 9
11.2 Quantity of tyre polymer in the sample . 9
11.3 Mass concentration of TRWP.10
12 Performance characteristics .10
12.1 General .10
12.2 Specific performance characteristics .10
12.3 Method detection limit .10
13 Test report .10
Annex A (informative) Recipe for calibration curves and stock solutions .12
Annex B (informative) Curie-point pyrolyser .14
Annex C (informative) Representative calibration curves and pyrograms .15
Annex D (normative) Calculation of TRWP detection limits .20
Annex E (normative) Calculation of results using dimer markers .21
Bibliography .23
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
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
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URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 45, Rubber and Rubber Products.
iv © ISO 2017 – All rights reserved

Introduction
Tyre and road wear particles (TRWP) are formed as a result of tread abrasion from the road surface,
and subsequent particle release to the environment. TRWP consist of tyre tread particles which include
[1]
incorporated material from the road surface (Kreider et al. 2010 ). The elastomeric fraction in TRWP
contained in soil or sediment materials is quantified in this document by direct pyrolysis-GC/MS
analysis. Mass concentration can be expressed on the basis of the rubber polymer, tyre tread, or TRWP.
This method has been used to measure the TRWP concentration in soil and sediment samples from three
[2] [3]
geographically separated regions (Unice et al. 2012 ; Unice et al. 2013 ). The airborne concentration
[4]
of TRWP in the PM fraction has also been characterized by a similar method (Panko et al. 2013 ).
Specific chemical markers are generated from intact TRWP by pyrolysis of sample specimens. The
chemical markers consist of characteristic and specific pyrolysis dimeric fragments of passenger
and truck tyre tread polymers including butadiene rubber, styrene-butadiene rubber, and isoprene
rubber. The polymer fragments generated by sample pyrolysis are subsequently separated by gas
chromatography, and identified by mass spectroscopy. The TRWP mass concentration is calculated
based on market average polymer use rates in tread, and prior characterization of the mineral content
of TRWP. Rubber polymer specificity is achieved by quantification of dimeric polymer fragments
[5] [6]
consisting of two monomer units (Kitamura et al. 2007 ; Harada et al. 2009 ). Repeatability is
achieved by the use of a deuterated internal standard of similar polymeric structure to the tyre tread
polymers. The internal standard corrects for variable analyte recovery caused by sample size, matrix
effects, and temporal variation in instrument response. The method is suitable for monitoring changes
in soil or sediment TRWP concentrations over time.
TECHNICAL SPECIFICATION ISO/TS 21396:2017(E)
Rubber — Determination of mass concentration of tire
and road wear particles (TRWP) in soil and sediments —
Pyrolysis-GC/MS method
WARNING 1 — 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.
WARNING 2 — Certain procedures specified in this document may involve the use or generation
of substances, or the generation of waste, that could constitute a local environmental hazard.
Reference should be made to appropriate documentation on safe handling and disposal after use.
1 Scope
This document specifies a method for the determination of the soil or sediment mass concentration
(μg/g) of tyre and road wear particles (TRWP) in environmental samples.
This document establishes principles for soil or sediment sample collection, the generation of pyrolysis
fragments from the sample, and the quantification of the generated polymer fragments. The quantified
polymer mass is used to calculate the concentration of TRWP in soil or sediment. These quantities are
expressed on a TRWP basis, which includes the mass of tyre tread and mass of road wear encrustations,
and can also be expressed on a tyre rubber polymer or tyre tread basis.
NOTE Tyre and road wear particles are a discrete mass of elongated particles generated at the frictional
interface between the tyre and roadway surface during the service life of a tyre. The particles consist of tyre
tread enriched with mineral encrustations from the roadway surface.
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 7270-1, Rubber — Analysis by pyrolytic gas-chromatographic methods — Part 1: Identification of
polymers (single polymers and polymer blends)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
deuterated internal standard
compound containing at least one deuterium molecule added to a sample in a fixed amount that is nearly
identical to the target analyte used to correct for instrument drift and matrix interference
3.2
dry mass
mass of solid dried in an oven for a specified time and at a specified temperature
3.3
monitoring
repeated measurement to follow changes over a period of time
3.4
percent moisture
mass of water in soil expressed as a percentage of oven dried mass
3.5
pyrolysis analysis
decomposition of organic polymeric molecules into characteristic fragments separated by gas
chromatography and quantified by mass spectroscopy
4 Principle
Tyre tread polymer is quantified using internal standard calibration and the peak area of characteristic
fragment ions corresponding to dimers of the raw polymer by pyrolysis-GC/MS. The thermal
decomposition products of cross-linked natural rubber (NR), styrene-butadiene rubber (SBR) and
butadiene rubber (BR) polymers depend on the abundance of polymers in the sample. SBR pyrolysis
generates butadiene, vinylcyclohexene (butadiene dimer) and styrene, whereas BR generates only
butadiene monomer and vinylcyclohexene. NR is associated with isoprene monomer and dipentene
(isoprene dimer). The dimer fragments have good specificity for rubber polymers, whereas both
[5]
anthropogenic and natural organic substances are sources of the monomer markers (Kitamura 2007 ).
Therefore, the monomeric pyrolysis marker compounds are subject to interference from non-TRWP
environmental sources, and are not suitable for quantification of TRWP mass concentration in soil or
sediment. One well-known example is styrene, which is generated from pyrolysis of both SBR and diesel
[7]
exhaust particles (Pierson and Brachaczek 1974 ). The tyre polymers, and pyrolysis fragment dimers
used for quantification of TRWP are shown in Figure 1.
Figure 1 — Dimeric pyrolysis products of tyre rubber polymers
5 Reagents
Use only reagents of recognized analytical grade.
5.1 Chloroform, analytical grade.
2 © ISO 2017 – All rights reserved

5.2 Helium, purity 99,999 5 % by volume.
6 Apparatus
6.1 Soil or sediment sampling — Equipment and consumable supplies.
6.1.1 Sampling device.
The sampling device shall be suitable for the collection of soil or sediment samples. Suitable devices
include pre-cleaned stainless steel hand trowels, coring tools or clamshell dredge devices. The collection
of a sediment sample with a clamshell dredge device is illustrated in Figure 2.
NOTE Photo courtesy of Cardno ChemRisk.
Figure 2 — Collection of sample with clamshell dredge device
6.1.2 Sample containers.
Samples should be collected in clean sample containers supplied by the laboratory, or clean sample
container handled in a manner consistent with laboratory standard operating procedures. The
placement of a soil sample into a sample container with a trowel is illustrated in Figure 3.
NOTE Photo courtesy of Cardno ChemRisk.
Figure 3 — Placement of sample in container with trowel
6.2 Equipment for analysis.
6.2.1 Laboratory oven, for drying field collected sample(s) at a temperature of 105 °C for 24 h in a
suitably clean laboratory-supplied container.
6.2.2 Sieve, for removing large aggregates unsuitable for the pyrolyser unit. The nominal opening for
dry sieving can be 1 mm.
6.2.3 Precision analytical balance, for determination of sample mass as collected, after oven drying,
and after dry sieving. Measurements shall be conducted in an environment of controlled temperature
and humidity. The balance shall be accurate to 0,01 mg and be maintained, calibrated and certified in
accordance with the manufacturer’s recommendations.
6.2.4 Pyrolyser, operating at a temperature of 670 °C for 5 s in a helium atmosphere with an induction
time of less than 0,2 s. A single-use or reusable sample holder shall be selected in accordance with the
manufacturer's recommendation. Examples of pyrolyser systems are provided in ISO 7270-1, and include
micro-furnace with quartz tube, Curie-point with holder, and platinum filament with holder. An example
of one type of pyrolyser that can be used is described in Annex B.
6.2.5 Gas chromatograph/mass spectrometer, operated and maintained in accordance with the
manufacturer’s instructions.
6.2.5.1 Gas chromatograph, as specified below:
— carrier gas flow rate: 1,0 ml/min to 2,0 ml/min;
— injector temperature: 300 °C;
— oven temperature programme: initial temperature 50 °C for 5 min, heating at 25 °C /min up to
300 °C, maintained at 300 °C for 10 min.
6.2.5.2 Column, as specified below:
— length: 25 m to 60 m;
— diameter: 0,25 mm to 0,35 mm;
4 © ISO 2017 – All rights reserved

— liquid phase: 5 % diphenyl-, 95 % polydimethylsiloxane;
— film thickness: 0,20 µm to 1,0 µm.
6.2.5.3 Mass spectrometer, quadrupole mass spectrometer, magnetic-sector-type mass spectrometer
or any other suitable type, having the characteristics specified below:
— interface temperature: 300 °C to 350 °C;
— ionization method: electron ionization;
— ion source temperature: 230 °C;
— ionizing voltage: 70 eV;
— scan range: mass/charge ratio: 35 m/z to 500 m/z.
7 Specimen preparation laboratory
The specimen preparation laboratories and sample containers selected for analysis shall be sufficiently
free of contamination that blank analyses demonstrate an absence of polymer as established by the
method detection limit (MDL). At least one laboratory blank analysis shall be performed for each type
of sample container used for sample collection, and following modifications to laboratory standard
operating procedures or equipment.
8 Measuring range
The range of SBR/BR polymer that can be determined in a soil or sediment sample is approximately
0,09 μg to 90 μg, and the range of NR polymer that can be determined is approximately 0,03 μg to 50 μg.
Assuming a total sample mass of 0,020 g, this mass range corresponds to a TRWP concentration range
in soil or sediment of approximately 24 μg/g to 28 000 μg/g.
NOTE The TRWP concentration range is based on Formula (E.2). For example, the low end of the TRWP
concentration range is (0,09 μg + 0,03 μg) / 0,5 / 0,5 / 0,020 g = 24 μg/g. The first factor of 0,5 accounts for
the polymer fraction in tyre tread. TRWP consists of tyre tread enriched with mineral encrustations from the
roadway surface. The second factor of 0,5 accounts for the fraction of tyre tread in TRWP.
9 Limit of detection
The TRWP limit of detection depends on mass of sample pyrolysed. In practice, sampling constraints
and the capacity of the pyrolysis unit determine the lowest achievable limit of detection. For a nominal
sample mass of 0,020 g, the limit of detection is approximately 24 μg/g TRWP in soil or sediment.
An alternative limit of detection can be achieved by changing the calibration curve range and mass
of internal standard used in the analysis. Alternative limits of detection based on adjustment of the
calibration curve range and internal standard masses shall be verified by a method detection limit study.
The target TRWP detection limit shall be determined as part of the sampling plan prior to sample
collection. The sample plan shall specify field and laboratory conditions sufficient to ensure that the
target detection limit satisfies the sample campaign goals and objectives. A sample-specific detection
limit shall be calculated based on the conditions of the analysis. The detection limit calculations are
specified in 11.1.
10 Procedure
10.1 General
The method is defined for a sample mass of oven-dried soil or sediment suitable for the pyrolyser
unit. Thermal energy is applied to a sample encapsulated in a pyrolyser in the absence of oxygen to
decompose the sample. Secondary reactions are minimized by rapid heating of the pyrolyser to the
target temperature. The nominal sample mass for the example pyrolysis unit described in Annex B is
0,020 g. The sample collection and laboratory pyrolysis-GC/MS procedure consists of the following six
steps and is described in 10.2 to 10.6 respectively:
a) sample collection;
b) deuterated internal standard preparation;
c) calibration curve preparation;
d) sample preparation;
e) sample pyrolysis with polymer decomposition under defined thermal conditions;
f) dimer measurement using gas-chromatographic (GC) separation and mass spectroscopy (MS).
The procedure relies on deuterated homopolymer internal standards to increase the precision and
accuracy of the measured TRWP concentration. The internal standard is used to correct for matrix
effects that affect polymer pyrolysis and fragment recovery. The internal standard also corrects for
changes in the mass spectrometer ion source condition and fluctuations in carrier gas flow rates. The
internal standards are deuterated polyisoprene (d-PI) and deuterated polybutadiene (d-PB), which are
polymers labelled with the minor stable hydrogen isotope deuterium. The pyrolysis-GC/MS thermal
decomposition products of d-PI and d-PB are discriminated based on retention time and mass to charge
ratio from the dipentene and vinylcyclohexene markers associated with NR and SBR/BR, respectively.
10.2 Sample collection
A soil or sediment sample is collected in clean laboratory supplied or approved sample containers.
The sample shall be collected using a clean device suitable for the collection of soil or sediment
samples, such as stainless steel hand trowels, coring tools or clamshell dredge devices. The standard
operating procedure for sample collection shall be approved by the laboratory. A chain-of-custody form
documenting sample collection and relinquishment shall be maintained. A soil or sediment mass of at
least 10 g to 50 g should be collected to ensure adequate homogenization.
10.3 Deuterated internal standard preparation
Deuterated standards d-PI (1,4-d8) and d-PB (1,4-d6) of known purity shall be obtained prior to
analysis (see Table 1). The purity of the standards shall be sufficiently high to prevent interference for
TRWP sample concentrations at or above the detection limit or reporting limit of the analysis.
A recipe for stock internal standard solution preparation that should be used is specified in Annex A.
Alternative recipes may be used to meet the objectives of the analysis. To prepare the stock solutions,
raw d-PI or d-PB polymer is weighed and placed in a graduated flask. Chloroform shall be poured
to two-thirds of the tot
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