ISO 19050:2015
(Main)Rubber, raw, vulcanised — Determination of metal content by ICP-OES
Rubber, raw, vulcanised — Determination of metal content by ICP-OES
ISO 19050:2015 describes the method of determination of both major and trace levels of metal contents in rubber ? raw, vulcanized ? by ICP-OES.
Caoutchouc brut, vulcanisé — Dosage de la teneur en métaux par ICP-OES
General Information
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 19050
First edition
2015-09-15
Rubber, raw, vulcanised —
Determination of metal content by
ICP-OES
Caoutchouc brut, vulcanisé — Dosage de la teneur en métaux par
ICP-OES
Reference number
ISO 19050:2015(E)
©
ISO 2015
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ISO 19050:2015(E)
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ISO 19050:2015(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Principle . 1
4 Reagents . 1
5 Apparatus . 2
6 Calibration . 3
7 Sample preparation . 4
7.1 General . 4
7.2 Sampling . 4
7.3 Decomposition of organic matter . 4
7.3.1 Wet oxidation . 4
7.3.2 Dry ashing . 4
7.3.3 Microwave digestion . . 5
7.4 Preparation of standard solution and test solution . 6
8 Procedure. 7
9 Test Report . 9
Annex A (normative) Calibration schedule .10
Annex B (informative) Process flow of atomization of sample in ICP-OES .11
Bibliography .12
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ISO 19050:2015(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 19050:2015(E)
Introduction
The ICP-OES (inductively coupled plasma – optical emission spectrophotometer) instrument is used to
determine the concentrations of certain elements in materials of interest. The main advantage of ICP-
OES over the AAS (atomic absorption spectroscopy) techniques in general is its multi-element capability,
its longer linear dynamic ranges and fewer condensed phase interferences. In addition, besides the
refractory compound-forming elements, elements such as iodine, phosphorus and sulfur are detected
with more sensitivity by the ICP-OES technique. ICP-OES is also known as ICP-AES (inductively coupled
plasma – atomic emission spectrophotometer).
ICP-OES was first introduced as a technique for trace elemental analysis. The technique experiences the
least interference of any of the commonly used analytical atomic spectrometry techniques. Chemical
interferences are largely eliminated by the high temperature of the plasma. Physical interferences can
be compensated for by taking advantage of the ICP’s multi-element capability.
In ICP-OES, the light emitted by the excited atoms and ions in the plasma is measured to obtain
information about the sample. Because the excited species in the plasma emit light at several different
wavelengths, the emission from the plasma is polychromatic. This polychromatic radiation has to be
separated into individual wavelengths so the emission from each excited species can be identified and
its intensity can be measured without interference from emission at other wavelengths.
An important feature of the ICP that is not common to most other emission sources is that since the sample
aerosol is introduced through the centre of the ICP, it can be surrounded by the high temperature plasma
for a comparatively long time, approximately 2 ms. It is this long residence time of the analyte particles in
the centre of the plasma that is largely responsible for the lack of matrix interferences in the ICP.
The determination described in this International Standard is important with respect to product safety
and the environment. ICP-OES is a state-of-the art instrument for accurate detection of the trace metals
in raw and vulcanized samples of rubber including latex.
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INTERNATIONAL STANDARD ISO 19050:2015(E)
Rubber, raw, vulcanised — Determination of metal
content by ICP-OES
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 — 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 describes the method of determination of both major and trace levels of
metal contents in rubber — raw, vulcanized — by ICP-OES.
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 123, Rubber latex — Sampling
ISO 124, Latex, rubber — Determination of total solids content
ISO 1795, Rubber, raw natural and raw synthetic — Sampling and further preparative procedures
ISO 18899:2013, Rubber — Guide to the calibration of test equipment
3 Principle
An aqueous sample is converted to an aerosol via a nebulizer. The aerosol is transported to the
inductively coupled plasma which has a high temperature zone (8 000 °C to 10 000 °C). The analytes
are heated (excited) to different (atomic and/or ionic) states and produce characteristic optical
emissions. These emissions are separated based on their respective wavelengths and their intensities
are measured (spectrometry). The intensities are proportional to the concentrations of analytes in the
aqueous sample. The quantification is carried out via an external multipoint linear standardization
obtained by comparing the emission intensity of an unknown sample with that of a standard sample. A
process flow of atomization of sample in ICP-OES is shown in Annex B.
4 Reagents
Use only reagents of recognized analytical grade, unless otherwise specified, and distilled or deionized
water or water of equivalent purity.
4.1 Ultra-pure grade of concentrated nitric acid, density 1,42 g/ml.
4.2 Ultra-pure grade of concentrated hydrochloric acid, density 1,19 g/ml.
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ISO 19050:2015(E)
4.3 Ultra-pure grade of concentrated sulfuric acid, density 1,83 g/ml.
4.4 Multi-element primary standard solution, traceable to NIST (National Institute of Standards
and Technology) or any national metrological institute (NMI).
4.5 Single-element primary standard solutions, traceable to NIST or any NMI.
4.6 Ammonium oxalate saturated solution.
4.7 Yttrium solution, 1 000 μg/g.
4.8 Diluted nitric acid.
4.9 Diluted HCl.
5 Apparatus
Usual laboratory apparatus and glassware and, in particular, the following.
5.1 ICP-OES system. A portion of the photons emitted by the ICP is collected with a lens or a concave
mirror. This focusing optic forms an image of the ICP on the entrance aperture of a wavelength selection
device such as a monochromator. The particular wavelength exiting the monochromator is converted to
an electrical signal by a photodetector. The signal is amplified and processed by the detector electronics,
then displayed and stored by a personal computer. Different components of the instruments are shown
in Figure 1. A description of the different components is given in 5.1.1 to 5.1.4.
5.1.1 Test solution introduction, to produce a steady aerosol of very fine droplets. There are three
basic parts to the sample introduction system as listed in 5.1.1.1 to 5.1.1.3.
5.1.1.1 Peristaltic pump, to draw up the test solution and deliver it to the nebulizer.
5.1.1.2 Nebulizer, to convert the solution to an aerosol that is sent to the spray chamber.
5.1.1.3 Spray chamber, to filter out the large, uneven droplets from the aerosol.
5.1.2 Energy source, to get atoms sufficiently energized such that they emit light. There are three
basic parts to the energy source as listed in 5.1.2.1 to 5.1.2.3.
5.1.2.1 Radio frequency generator, to generate an oscillating electro-magnetic field at a frequency of
27,12 MHz. This radiation is directed to the load coil. Equipment are also available with electro-magnetic
field at a frequency of 40,68 MHz.
5.1.2.2 Load coil, to deliver the radiation to the torch.
5.1.2.3 Torch, having argon flowing through it which will form a plasma in the RF field.
5.1.3 Spectrometer, to diffract the white light from the plasma into wavelengths. There are several
types of spectrometers used for ICP. Regardless of type, all of them use a diffraction grating.
5.1.4 Detector, to measure the intensity of the wavelengths. The detector is a silicon chip that is
composed of many individual photo-active sections called “picture elements”. These picture elements, or
pixels, will build up charge as photons impinge on them. Individual pixels are of a size such that they can
be used to measure individual wavelengths.
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ISO 19050:2015(E)
5.2 Analytical balance, capable of weighing to the nearest ± 0,1 mg.
5.3 Micro syringe, calibrated.
5.4 Hot plate.
5.5 Pipettes, of different capacities i.e. 10 ml, 20 ml.
5.6 Micro-Kjeldahl digestion flask.
5.7 Muffle furnace.
5.8 TFM (tetrafluoroethylene modified) vessel.
5.9 Microwave digestion system.
5.10 Sample rack of autosampler.
5.11 Filter paper, Whatman No. 44.
5.12 Silica or platinum dish.
Figure 1 — Different components of a typical ICP-OES instrument
6 Calibration
The instrument shall be calibrated in accordance with the schedule given in Annex A.
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ISO 19050:2015(E)
7 Sample preparation
7.1 General
There are four major steps involved in the analysis of metal contents.
a) obtaining a representative laboratory sample from the bulk received for testing;
b) decomposition of organic matter;
c) separation and concentration of the element of interest;
d) determination.
7.2 Sampling
For solid rubber, take the laboratory sample and prepare the test piece in accordance with the method
specified in ISO 1795.
For latex, take the la
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