ISO 10638:2017

INTERNATIONAL ISO
STANDARD 10638
Second edition
2017-07
Rubber — Identification
of antidegradants by gas
chromatography/mass spectrometry
Caoutchouc — Identification des antidégradants par
chromatographie en phase gazeuse/spectrométrie de masse
Reference number
ISO 10638:2017(E)
©
ISO 2017

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ISO 10638:2017(E)

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© 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
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ISO 10638:2017(E)

Contents  Page
Foreword .iv
Introduction .v
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 1
4  Principle . 1
5  Thermal-desorption method . 2
5.1 Reagents and materials . 2
5.2 Apparatus . 2
5.3 Sampling . 2
5.4 Procedure . 3
6  Solvent-extraction method. 3
6.1 Reagents and materials . 3
6.2 Apparatus . 4
6.3 Sampling . 4
6.4 Procedure . 4
7  Analysis . 4
7.1 General . 4
7.2 Procedure . 4
7.3 Important observations for analysis . 5
8  Test report . 5
Annex A (normative) Antidegradants covered by this document . 6
Annex B (informative) Chromatograms and mass spectra .10
Annex C (informative) Determination of gas-chromatographic retention index .42
Bibliography .45
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ISO 10638:2017(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on 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 the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 45, Rubber and rubber products,
Subcommittee SC 2, Testing and analysis.
This second edition cancels and replaces the first edition (ISO 10638:2010), which has been technically
revised with the following changes:
— trap coolant has been removed from the reagents;
— a calibration procedure for the apparatus has been added;
— test conditions have been added;
— a data analysis clause (Clause 7) has been added.
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ISO 10638:2017(E)

Introduction
Most rubber products contain antidegradants to extend the life of the product, the type of
antidegradant depending on the service conditions to which a particular product will be exposed.
Doubts are increasingly being expressed about the negative impact which rubber containing certain
antidegradants can have on the environment. However, demonstrating the presence of antidegradants
in rubber products is not easy.
There are methods of qualitative analysis, specified in International Standards such as ISO 4645,
which use thin-layer chromatography. This requires a highly skilled operator with a great amount of
knowledge and experience, as well as the use of standard reference materials.
The gas chromatography/mass spectrometry technique specified in this document is an efficient
method suitable for identifying antidegradants contained in rubber products, as well as in the raw-
rubber and the unvulcanized-rubber compounds used to make such products.
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INTERNATIONAL STANDARD ISO 10638:2017(E)
Rubber — Identification of antidegradants by gas
chromatography/mass spectrometry
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 and to
ensure compliance with any national regulatory conditions.
WARNING 2 — Certain procedures specified in this document might 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 using gas chromatography/mass spectrometry, for the identification
of antidegradants in raw rubbers, latices, unvulcanized-rubber compounds and vulcanized-rubber
products. It is applicable to the 31 types of antidegradant listed in Annex A. The method specified is
qualitative and is not intended for quantitative analysis.
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 123, Rubber latex — Sampling
ISO 124, Latex, rubber — Determination of total solids content
ISO 1407:2011, Rubber — Determination of solvent extract
ISO 1795, Rubber, raw natural and raw synthetic — Sampling and further preparative procedures
3  Terms and definitions
No terms and definitions are listed in this document.
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 http:// www .iso .org/ obp
4  Principle
Antidegradants are recovered from samples by thermal desorption or solvent extraction. For
thermal-desorption method, the fume generated from heating test samples is to be analysed after
being separated through the gas chromatograph/mass spectrometer which is connected to a heating
and desorbing device. For solvent-extraction method, the extract of test samples obtained by solvent
extraction process is to be separated and analysed by the gas chromatograph/mass spectrometer.
The type of antidegradant recovered is identified by the mass spectrum that is produced after passing
the antidegradant through a gas chromatograph and mass spectrometer connected in tandem. The
retention index can be used as a supplementary means of identification if necessary.
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ISO 10638:2017(E)

5  Thermal-desorption method
5.1  Reagents and materials
5.1.1  Gas chromatograph carrier gas, helium.
5.2  Apparatus
5.2.1  Thermal-desorption apparatus or equivalent, connectable to the gas chromatograph and
which can be heated up to 350 °C.
NOTE An example of an equivalent apparatus is a pyrolyzer in which the heating temperature is kept low.
5.2.2  Gas chromatograph/mass spectrometer.
5.2.2.1  Gas chromatograph, as specified below:
— carrier gas flow rate: 1,0 ml/min to 2,0 ml/min;
— injector temperature: 300 °C to 350 °C;
— maximum oven temperature: 350 °C.
5.2.2.2  Column, as specified below:
— length: 25 m to 60 m;
— diameter: 0,25 mm to 0,35 mm;
— liquid phase: 5 % diphenyl-, 95 % polydimethylsiloxane;
— film thickness: 0,20 µm to 0,35 µm.
Other types of column (e.g. 100 % polydimethylsiloxane) may be used if the retention index given in
Annex A, or determined as described in Annex C, is not utilized in the analysis.
5.2.2.3  Mass spectrometer, quadrupole mass spectrometer, magnetic-sector-type mass spectrometer
or any other suitable type, having the characteristics specified below:
— interface temperature: 300 °C;
— ionization method: electron ionization;
— ion source temperature: 230 °C to 300 °C;
— ionizing voltage: 70 eV;
— scan range: mass/charge ratio (m/z): 50 to 600.
5.3  Sampling
5.3.1  In the case of latex, carry out sampling in accordance with ISO 123 and dry the sample in
accordance with ISO 124.
5.3.2  In the case of raw rubber, carry out sampling in accordance with ISO 1795.
5.3.3  In the case of rubber compound which includes vulcanized or unvulcanized rubber, take out a
sample that represents the whole (e.g. by sampling from the core part). Clean the surface of the sample.
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ISO 10638:2017(E)

5.4  Procedure
WARNING — Persons following the procedure specified in this subclause are expected to
be familiar with analysis using gas chromatography/mass spectrometry. In addition, it is
assumed that the gas chromatograph/mass spectrometer is operated in accordance with the
manufacturer’s instruction manual and that it is maintained in an optimum condition. Detailed
procedures for operation of the equipment are therefore not included.
5.4.1  Adjust the mass/charge ratio (m/z) with calibration reference material in accordance with the
instruction manual of the apparatus.
5.4.2  Set each apparatus as follows.
5.4.2.1  Thermal-desorption apparatus
― thermal-desorption temperature: 350 °C.
5.4.2.2  Gas chromatograph
— carrier gas flow rate: 1 ml/min to 2 ml/min;
— injector temperature: 300 °C to 350 °C;
— temperature programme:
a) initial temperature: 40 °C to 80 °C;
b) rate of temperature rise: 10 °C/min to 25 °C/min;
c) final temperature: 320 °C to 350 °C — set the final temperature of column oven at or below the
highest temperature of column used;
d) retention time: 10 min to 30 min.
5.4.2.3  Mass spectrometer
― interface temperature: 300 °C;
― ionization method: electron ionization;
― ion source temperature: 230 °C to 300 °C;
― ionizing voltage: 70 eV;
― scan range: mass/charge ratio (m/z): 50 to 600.
5.4.3  Put approximately 0,2 mg to 2 mg of sample into a sample holder.
5.4.4  Put the sample holder (5.4.3) in the thermal-desorption apparatus and start the gas
chromatography/mass spectrometry measurement in order to obtain the gas chromatogram and mass
spectrum. For a more accurate identification, the gas-chromatographic retention index can be determined
as described in Annex C.
6  Solvent-extraction method
6.1  Reagents and materials
6.1.1  Extraction solvent: acetone of analytical reagent grade.
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ISO 10638:2017(E)

6.1.2  Gas chromatograph carrier gas, helium.
6.2  Apparatus
6.2.1  Soxhlet extractor, as specified in ISO 1407.
6.2.2  Gas chromatograph/mass spectrometer, as specified in 5.2.2.
6.3  Sampling
See 5.3.
6.4  Procedure
6.4.1  Adjust the mass/charge ratio (m/z) according to 5.4.1 and set gas chromatograph/mass
spectrometer conditions as specified in 5.4.2.2 and 5.4.2.3.
6.4.2  Carry out a Soxhlet extraction, using acetone as solvent, on approximately 2 g of sample cut
into cubes measuring 2 mm or less, continuing the extraction for approximately 8 h in accordance with
ISO 1407:2011, method A.
If the 2 g sample does not give enough antidegradant, continue the extraction with more sample.
6.4.3  Concentrate the extract to between 10 ml and 20 ml and inject 1 µl of the concentrated extract
into the gas chromatograph, and start the gas chromatography/mass spectrometry measurement in
order to obtain the gas chromatogram and mass spectrum. For a more accurate identification, the gas-
chromatographic retention index can be determined as described in Annex C.
If the raw-rubber or unvulcanized-rubber compound is soluble in acetone, the thermal-desorption
method should be used instead of the solvent-extraction method.
7  Analysis
7.1  General
Analyse the data as specified in 7.2 for the detected substances. The characteristic mass/charge ratio
(m/z) of each substance is provided in Annex A. The characteristic peak assignment and the mass
spectrum are provided in Annex B.
7.2  Procedure
7.2.1  Display the mass spectrum of each chromatographic peak obtained by the procedure in 5.4 or 6.4.
7.2.2  Compare the obtained mass spectrum to Figures B.1 to B.31 to find the most similar pattern.
NOTE Mass-spectrum search systems are available on the market to help with this procedure.
7.2.3  Identify the antidegradants using Table A.1.
When gas-chromatographic retention indices have been obtained in the earlier steps, verify that they
conform to the identified antidegradants’ retention indices in Table A.1.
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ISO 10638:2017(E)

7.3  Important observations for analysis
7.3.1  Make sure to analyse the whole spectrum including the major mass/charge ratio (m/z) and
the relative intensity. The identification is more accurate when mass spectra and gas-chromatographic
retention indices are examined together.
7.3.2  Note that more than one antidegradants are often found upon identification.
7.3.3  Some types of antidegradants are made of a mixture of several substances. In such cases, the
gas chromatogram includes more than one set of peaks. Since the composition differs depending on the
manufacturer or on the grade, the ratio of peak areas or heights wi
...