ISO 15672:2000

INTERNATIONAL ISO
STANDARD 15672
First edition
2000-07-15
Rubber and rubber additives —
Determination of total nitrogen content
using an automatic analyser
Caoutchouc et additifs pour caoutchouc — Dosage de l'azote total à l'aide
d'un analyseur automatique
Reference number
ISO 15672:2000(E)
© ISO 2000

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ISO 15672:2000(E)
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ISO 15672:2000(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 com-
mittees. 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 liai-
son with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 15672 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products,
Subcommittee SC 2, Testing and analyses.
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INTERNATIONAL STANDARD ISO 15672:2000(E)
Rubber and rubber additives — Determination of total nitrogen
content using an automatic analyser
WARNING — Persons using this International Standard should be familiar with normal laboratory practice.
This 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.
1 Scope
This International Standard specifies an instrumental (automatic analyser) method for the determination of total
nitrogen in rubber and rubber additives.
2 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
2.1
sample
unit selected to represent the material to be analysed
2.2
test portion
actual material used in the analysis
2.3
control sample
material with a recognized level of nitrogen, analysed with each set of test portions
3 Principle
3.1 Specified is a reliable, rapid, instrumental (automatic) method for determining total nitrogen in rubber and rub-
ber additives. The nitrogen is determined by a single instrumental procedure consisting of weighing a test portion,
placing it in the instrument and initiating the (subsequently automatic) analytical process. The analysis may be con-
trolled manually to a limited degree, and a capability to perform computations automatically may be provided by the
instrument used to perform the analysis.
3.2 The actual process can vary substantially from instrument to instrument because a variety of means can be
used to meet the primary requirements of the method. The method includes the following:
a) conversion of nitrogen-containing materials to nitrogen oxides in an oxygen stream;
b) reduction of the nitrogen oxides to elemental nitrogen by passing them over copper at an elevated temperature;
c) determining the nitrogen by one of three detection schemes.
3.3 In the thermal conductivity detection configuration, the combustion gases are conducted through a series of
thermal conductivity detectors and gas absorbers aligned so that the gases pass first through the sample side of a
water vapour detector, through a water vapour absorber and through the reference side of the detector. The gases
are then conducted through the sample side of a carbon dioxide detector, through a carbon dioxide absorber and
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ISO 15672:2000(E)
through the reference side of the detector. Finally, the resultant gases, which contain only nitrogen and the carrier
gas, pass through the sample side of a nitrogen detector and are vented. For this detector, high-purity carrier gas is
used as the reference gas. In this way, the detectors determine the thermal conductivities solely of the specified com-
ponents.
3.4 In the combined absorbance/conductivity detection configuration, the carbon dioxide and water vapour are
determined by infrared detection, using an aliquot of the combustion gases from which only the halides and sulfur ox-
ides have been removed. These detectors determine the infrared absorbance of the pertinent gases at precise wave-
length windows so that the absorbances result from only the specified components. In such a system, nitrogen is
determined by thermal conductivity, using a second aliquot of the gases additionally treated to reduce the nitrogen
oxides to nitrogen and to remove the residual oxygen, carbon dioxide and water vapour.
3.5 In the modified chromatographic detection configuration, which is essentially a modified gas chromato-
graphic system, the nitrogen, carbon dioxide and water vapour in the treated combustion gases are eluted from a
chromatographic column and determined (at appropriate retention times) by thermal conductivity detection.
3.6 The concentration of nitrogen is calculated in each configuration as a function of the following:
a) the measured instrumental (automatic analyser) responses per unit mass for elemental nitrogen (established via
instrument calibration);
b) the mass of the test portion.
4 Requirements for apparatus
4.1 Because a variety of instrumental (automatic analyser) component configurations can be used satisfac
...