ISO 6101-6:2011

Rubber — Determination of metal content by atomic absorption spectrometry — Part 6: Determination of magnesium content

ISO 6101-6:2011 specifies an atomic absorption spectrometric method for the determination of the magnesium content of natural rubber latex concentrate, raw natural rubber and products made from natural rubber.

Caoutchouc — Dosage du métal par spectrométrie d'absorption atomique — Partie 6: Dosage du magnésium

General Information

• Status: Withdrawn
• Publication Date: 08-Nov-2011
• Withdrawal Date: 08-Nov-2011
• ICS: 83.060 - Rubber
• Technical Committee: ISO/TC 45/SC 2 - Testing and analysis
• Drafting Committee: ISO/TC 45/SC 2/WG 5 - Chemical tests
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 25-Sep-2018
• Completion Date: 25-Sep-2018

Relations

• Revised: ISO 6101-6:2018 - Rubber — Determination of metal content by atomic absorption spectrometry — Part 6: Determination of magnesium content
• Effective Date: 10-Dec-2016

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 6101-6
First edition
2011-11-15
Rubber — Determination of metal content
by atomic absorption spectrometry —
Part 6:
Determination of magnesium content
Caoutchouc — Dosage du métal par spectrométrie d'absorption
atomique —
Partie 6: Dosage du magnésium
Reference number
©
ISO 2011
©  ISO 2011
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56  CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2011 – All rights reserved

Contents Page
Foreword . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principle . 2
5 Reagents . 2
6 Apparatus . 2
7 Sampling . 3
8 Procedure . 3
8.1 Test portion . 3
8.2 Preparation of test solution . 3
8.3 Preparation of calibration graph . 3
8.4 Determination . 4
8.5 Expression of results . 5
9 Precision . 6
10 Test report . 6
Annex A (informative) Method of standard additions . 7
Annex B (informative) Precision . 8

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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. 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 document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 6101-6 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee
SC 2, Testing and analysis.
ISO 6101 consists of the following parts, under the general title Rubber — Determination of metal content by
atomic absorption spectrometry:
 Part 1: Determination of zinc content
 Part 2: Determination of lead content
 Part 3: Determination of copper content
 Part 4: Determination of manganese content
 Part 5: Determination of iron content
 Part 6: Determination of magnesium content

iv © ISO 2011 – All rights reserved

INTERNATIONAL STANDARD ISO 6101-6:2011(E)

Rubber — Determination of metal content by atomic absorption
spectrometry —
Part 6:
Determination of magnesium content
WARNING — Persons using this part of ISO 6101 should be familiar with normal laboratory practice.
This part of ISO 6101 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.
IMPORTANT — Certain procedures specified in this part of ISO 6101 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 part of ISO 6101 specifies an atomic absorption spectrometric method for the determination of the
magnesium content of natural rubber latex concentrate, raw natural rubber and products made from natural
rubber.
2 Normative references
The following referenced documents are indispensable for the application 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 247, Rubber — Determination of ash
ISO 648:2008, Laboratory glassware — Single-volume pipettes
ISO 835:2007, Laboratory glassware — Graduated pipettes
ISO 1042:1998, Laboratory glassware — One-mark volumetric flasks
ISO 1772, Laboratory crucibles in porcelain and silica
ISO 1795, Rubber, raw natural and raw synthetic — Sampling and further preparative procedures
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
natural rubber latex concentrate
natural rubber latex from Hevea brasiliensis, containing ammonia and/or other preservatives, and which has
been subjected to some process of concentration
3.2
raw natural rubber
natural rubber, usually in bales or packages, forming the starting material for the manufacture of rubber
articles
4 Principle
A test portion is ashed at 550 °C  25 °C, or at 950 °C  25 °C for rubber products having a high carbon black
content. The ash is dissolved in dilute nitric acid. The solution is aspirated into an atomic absorption
spectrometer and the absorption is measured at a wavelength of 285,2 nm, using a magnesium hollow-
cathode lamp as the magnesium emission source.
5 Reagents
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade and only
distilled water or water of equivalent purity.
5.1 Concentrated nitric acid, density  1,41 g/cm .
5.2 Dilute nitric acid, 1,6 % (by mass), prepared by carefully pipetting 11,5 cm of concentrated nitric
acid (5.1) into a 1 000 cm one-mark volumetric flask, making up to the mark with water and mixing thoroughly.
5.3 Standard magnesium stock solution, containing 1 mg of Mg per cubic centimetre. Use a
commercially available standard magnesium solution.
5.4 Standard magnesium solution, containing 10 µg of Mg per cubic centimetre, prepared by carefully
3 3
pipetting 10 cm of standard magnesium stock solution (5.3) into a 1 000 cm one-mark volumetric flask,
making up to the mark with dilute nitric acid (5.2) and mixing thoroughly. Prepare this solution preferably on
the day of use.
6 Apparatus
6.1 Atomic absorption spectrometer, fitted with a burner fed with acetylene and air compressed to at
least 60 kPa and 300 kPa, respectively, and also fitted with a magnesium hollow-cathode lamp as the
magnesium emission source. The instrument shall be operated in accordance with the manufacturer’s
instructions for optimum performance.
6.2 Balance, accurate to 0,1 mg.
6.3 Muffle furnace, capable of being maintained at a temperature of 550 °C  25 °C or 950 °C  25 °C.
3 3 3
6.4 One-mark volumetric flasks, glass-stoppered, of capacities 50 cm , 100 cm and 1 000 cm ,
complying with the requirements of ISO 1042:1998, class A.
3 3 3 3
6.5 Volumetric pipettes, of capacities 5 cm , 10 cm , 20 cm and 50 cm , complying with the
requirements of ISO 648:2008, class A.
2 © ISO 2011 – All rights reserved

6.6 Graduated pipette, of capacity 1 cm , complying with the requirements of ISO 835:2007, class A.
6.7 Steam bath.
6.8 Borosilicate-glass rod, for use as a stirrer.
6.9 Crucible, of silica, porcelain or borosilicate glass, of nominal capacity 50cm , complying with the
requirements of ISO 1772.
6.10 Ashless filter paper.
7 Sampling
Carry out sampling in accordance with one of the methods specified in ISO 123 for natural rubber latex, in
accordance with ISO 1795 for raw, natural rubber and on a milled or finely cut test sample representative of
the whole sample for products made from natural rubber.
8 Procedure
8.1 Test portion
8.1.1 For natural rubber latex concentrate, take a portion of thoroughly mixed latex containing about 10 g of
total solids, make into a thin film by pouring the portion onto a glass plate, dry to constant mass as specified in
ISO 124 and cut into small pieces.
8.1.2 For raw, natural rubber, take the test portion from a test sample prepared in accordance with
ISO 1795.
8.1.3 For products made from natural rubber, take the test portion from a milled or finely cut test sample.
8.2 Preparation of test solution
8.2.1 Ashing of test portion (destruction of organic matter)
Weigh out, to the nearest 0,1 mg, a test portion of approximately 3 g. Wrap the test portion in an ashless filter
paper and place in a crucible of nominal capacity 50 cm . Heat the crucible containing the test portion over a
bunsen burner or electric heater until all volatile material has evolved. Take care that the rubber does not
ignite. If any material is lost due to spurting or frothing, repeat the above procedure with a new test portion.
Place in a muffle furnace set at a temperature of 550 °C  25 °C (or 950 °C  25 °C for rubbers with a high
carbon black content) and leave overnight or until all carbonaceous material is burned off.
8.2.2 Dissolution of inorganic residue
Add 10 cm of dilute nitric acid (5.2) to the cooled residue. Cover with a watch glass and heat on a steam bath
for at least 30 min. Allow to cool to ambient temperature. Filter the contents of the crucible into a 50 cm one-
mark volumetric flask, rinsing the crucible and making up to the mark with dilute nitric acid (5.2).
8.3 Preparation of calibration graph
8.3.1 Preparation of standard solutions
Into a series of five 100 cm one-mark volumetric flasks, introduce, using pipettes, the volumes of standard
magnesium solution (5.4) indicated in Table 1. Make up to the mark with dilute nitric acid (5.2) and mix
thoroughly.
Prepare the set of calibration solutions on the same day as the determination.
Table 1 — Standard calibration solutions
Volume of standard magnesium Mass of magnesium contained in
solution 1 cm
cm μg
50 5
20 2
10 1
5 0,5
0 0
8.3.2 Spectrometric measurements
Switch on the spectrometer sufficiently in advance to ensure stabilization. With the magnesium hollow-
cathode lamp suitably positioned, adjust the wavelength to 285,2 nm and the sensitivity and slit aperture
according to the characteristics of the instrument.
Adjust the pressure and flow rate of the air and of the acetylene in accordance with the manufacturer’s
instructions so as to obtain a clear, blue, non-luminous, oxidizing flame, suited to the characteristics of the
particular spectrometer being used.
Aspirate the set of calibration solutions in succession into the flame and measure the absorbance of each
solution twice, averaging the readings. Take care that the aspiration rate is constant throughout this process.
Aspirate water through the burner after each measurement.
8.3.3 Plotting the calibration graph
Plot a graph having, for example, the masses, in micrograms, of magnesium contained in 1 cm of the
calibration solutions as abscissae and the corresponding values of absorbance, corrected for the absorbance
of the calibration blank, as ordinates. Represent the points on the graph by the best straight line as judged
visually or as calculated by a least-squares fitting method.
8.4 Determination
8.4.1 Spectrometric measurements
Carry out duplicate spectrometric measurements at a wavelength of 285,2 nm on the test solution prepared in
8.2.2, following the procedure specified in 8.2.
8.4.2 Dilution
If the instrument response for the test solution is greater than that found for the calibration
...