ISO 19242:2015

Rubber — Determination of total sulfur content by ion chromatography

ISO 19242:2015 specifies a method for the determination of the total sulfur content of raw rubber and unvulcanized or vulcanized rubber compounds by ion chromatography following the preparation of a sample solution using either a tubular furnace combustion or an oxygen combustion flask method. The tubular furnace combustion method is applicable for rubbers with sulfur content less than 0,1 % as it is possible that the oxygen combustion flask method will not give sufficiently accurate results. The oxygen combustion flask method is not applicable to rubbers containing a metal salt that forms an insoluble metal sulfate, such as barium sulfate.

Caoutchouc — Détermination de la teneur en soufre total par chromatographie ionique

General Information

• Status: Withdrawn
• Publication Date: 03-Jun-2015
• Withdrawal Date: 03-Jun-2015
• ICS: 83.060 - Rubber
• Technical Committee: ISO/TC 45/SC 2 - Testing and analysis
• Drafting Committee: ISO/TC 45/SC 2 - Testing and analysis
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 07-Oct-2021

Relations

• Revised: ISO 19242:2021 - Rubber — Determination of total sulfur content by ion chromatography
• Effective Date: 17-Jul-2021

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 19242
First edition
2015-06-15
Rubber — Determination of total
sulfur content by ion chromatography
Caoutchouc — Détermination de la teneur en soufre total par
chromatographie ionique
Reference number
ISO 19242:2015(E)
©
ISO 2015

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ISO 19242:2015(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2015, 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 19242:2015(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Principle . 1
3.1 Combustion . 1
3.1.1 Tubular furnace combustion method . 1
3.1.2 Oxygen combustion flask method . 2
3.2 Determination . 2
4 Reagents . 2
5 Apparatus . 2
6 Procedure. 3
6.1 Preparation of sample solutions . 3
6.1.1 Tubular furnace combustion method . 3
6.1.2 Oxygen combustion flask method . 3
6.2 Determination of sulfate by ion chromatography . 3
6.2.1 Setting up the ion chromatograph . 3
6.2.2 Measuring calibration solutions . 3
6.2.3 Measuring blank solutions and sample solutions . 3
7 Calculations. 4
8 Precision . 4
9 Test report . 4
Annex A (normative) Preparation of sample solutions by the tubular furnace
combustion method . 5
Annex B (normative) Preparation of sample solutions by the oxygen combustion flask method .8
Annex C (informative) Examples of conditions for ion chromatography .11
Annex D (informative) Precision data from an interlaboratory test programme .12
Bibliography .14
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ISO 19242:2015(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 meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 45, Rubber and rubber products, Subcommittee
SC 2, Testing and analysis.
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ISO 19242:2015(E)

Introduction
Titration methods using thorin, a toxic arsenic compound as a reagent, have been used to determine
the total sulfur content in raw rubber and rubber compounds. In this International Standard the sulfur
in a test piece is burnt and oxidized to sulfur dioxide, which is then absorbed into a hydrogen peroxide
solution and converted to sulfuric acid for determination by ion chromatography.
No hazardous reagents are required, thus improving the working environment as well as being eco-
friendly. In addition, ion chromatography is used worldwide for its simplicity and high accuracy.
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INTERNATIONAL STANDARD ISO 19242:2015(E)
Rubber — Determination of total sulfur content by ion
chromatography
WARNING 1 — Persons using this International Standard should be familiar with normal
laboratory practice. This International Standard 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 — The use of this International Standard pre-supposes sufficient working knowledge
of the principles and techniques of ion chromatography for the analyst to perform the operations
described and interpret the results correctly.
CAUTION — Certain procedures specified in this International Standard 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 International Standard specifies a method for the determination of the total sulfur content of
raw rubber and unvulcanized or vulcanized rubber compounds by ion chromatography following the
preparation of a sample solution using either a tubular furnace combustion or an oxygen combustion
flask method.
The tubular furnace combustion method is applicable for rubbers with sulfur content less than 0,1 % as
it is possible that the oxygen combustion flask method will not give sufficiently accurate results.
The oxygen combustion flask method is not applicable to rubbers containing a metal salt that forms an
insoluble metal sulfate, such as barium sulfate.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 1795, Rubber, raw natural and raw synthetic — Sampling and further preparative procedures
ISO 4661-2, Rubber, vulcanized — Preparation of samples and test pieces — Part 2: Chemical tests
3 Principle
3.1 Combustion
3.1.1 Tubular furnace combustion method
A test piece is burnt in an oxygen stream in a tubular furnace with an electrical heater. The sulfur in the
test piece is oxidized to sulfur dioxide, which is absorbed into hydrogen peroxide solution and converted
to sulfuric acid.
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ISO 19242:2015(E)

3.1.2 Oxygen combustion flask method
A test piece is burnt in the presence of oxygen in a flask. The sulfur in the test piece is oxidized to sulfur
dioxide, which is absorbed into hydrogen peroxide solution and converted to sulfuric acid.
3.2 Determination
The sulfate from either the tubular furnace combustion or the oxygen combustion flask method is
quantitatively analysed by ion chromatography, and the result is converted to the total sulfur content of
the original rubber sample.
4 Reagents
Use only reagents of recognized analytical grade and only water as specified in 4.1. The reagents for
the tubular furnace combustion method are given in A.2. The reagents for the oxygen combustion flask
method are given in B.2.
4.1 Water, of grade 1 or higher as specified in ISO 3696.
4.2 Sulfate stock standard solution, of a commercial standard solution with a certified sulfate
3
concentration, e.g. 1 000 mg/dm of sulfate, traceable to national standards.
Observe the manufacturer’s expiry date or recommended shelf-life.
4.3 Sulfate calibration solutions, prepared by dilution of the sulfate stock standard solution (4.2)
with water (4.1).
Prepare at least four solutions of different concentration of sulfate covering the expected concentration
from the sample. The solutions shall be prepared every analytical day.
4.4 Eluent solution, capable of eluting sulfate to a proper retention time in selected column.
Follow the column manufacturer’s instructions. Some examples of eluent are shown in Annex C.
5 Apparatus
5.1 Balance, of accuracy to the nearest 0,1 mg.
5.2 Apparatus for the tubular furnace combustion method, as specified in A.3.
5.3 Apparatus for the oxygen combustion flask method, as specified in B.3.
5.4 Ion chromatograph, consisting of the pump to supply eluent, injection valve, column and
conductivity detector specified as follows:
3 3
— Pump: capable of delivering a constant flow within the range of 0,1 cm /min to 2,0 cm /min;
— Injection valve: capable of injecting a constant volume of solution;
— Column: filled with anion exchange resin suitable for resolving sulfates from other inorganic anions.
Some examples are shown in Annex C;
— Suppressor: used for reducing the conductivity of high ionic eluent;
— Detector: for detecting conductivity.
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ISO 19242:2015(E)

An ion chromatograph fitted with a suppressor is suitable for sensitive analysis (see Figure 1). The
suppressor is attached between the column and the detector. However, an ion chromatograph without a
suppressor may also be selected (see Figure 2). For the conditions of these methods, see Annex C.
Figure 1 — Example of basic ion chromatography system with suppressor
Figure 2 — Example of basic ion chromatography system without suppressor
6 Procedure
6.1 Preparation of sample solutions
6.1.1 Tubular furnace combustion method
Follow the method specified in Annex A. Repeat the procedure to create two solutions for each sample.
6.1.2 Oxygen combustion flask method
Follow the method specified in Annex B. Repeat the procedure to create two solutions for each sample.
6.2 Determination of sulfate by ion chromatography
6.2.1 Setting up the ion chromatograph
Set up the ion chromatograph in accordance with the manufacturer’s instructions.
6.2.2 Measuring calibration solutions
Inject the calibration solutions in order of increasing concentration and measure the conductivity of
sulfate peak area in each solution. Determine the correlation formula (calibration curve) by plotting the
peak area as a function of concentration by means of linear regression.
6.2.3 Measuring blank solutions and sample solutions
Inject the blank solutions and sample solutions (created in 6.1) to measure the peak area. Then determine
the sulfate concentration of the blank C and that of the individual sample solution C by using the
B S
calibration curve determined in 6.2.2.
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ISO 19242:2015(E)

7 Calculations
Calculate the sulfur content of the sample in percentage from each value determined in 6.2.3. Average
the two content values and round to the second decimal place, using the following formula:
()CC−×V 32,06
S B
××100
W×10
...