ISO 6101-2:2019

Rubber — Determination of metal content by atomic absorption spectrometry — Part 2: Determination of lead content

This document specifies an atomic absorption spectrometric method for the determination of the lead content of rubbers. The method is applicable to raw rubber and rubber products. There is no limit to the concentration of lead that can be determined. High or low concentrations can be determined, provided that suitable adjustments are made to the mass of the test portion and/or the concentration of the solutions used. The use of the standard-additions method might lower the bottom limit of detection.

Caoutchouc — Détermination de la teneur en métal par spectrométrie d'absorption atomique — Partie 2: Dosage du plomb

General Information

• Status: Published
• Publication Date: 28-Nov-2019
• 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: 9093 - International Standard confirmed
• Start Date: 22-Jan-2025
• Completion Date: 13-Dec-2025

Relations

• Revises: ISO 6101-2:1997 - Rubber — Determination of metal content by atomic absorption spectrometry — Part 2: Determination of lead content
• Effective Date: 23-Apr-2020

Overview

ISO 6101-2:2019 - Rubber - Determination of metal content by atomic absorption spectrometry - Part 2: Determination of lead content specifies an atomic absorption spectrometric (AAS) method for measuring lead (Pb) content in raw rubber and rubber products. The procedure covers sample preparation (including special treatment for halogenated rubbers), ash/digestion, solution preparation, calibration and spectrometric measurement. The method supports both flame AAS and electrothermal (graphite furnace) atomization and allows determination over a wide concentration range (no upper concentration limit), with the standard-additions technique available to improve the lower limit of detection.

Key topics and technical requirements

• Scope and applicability: Applies to raw rubber, latex and finished rubber products; suitable for a broad range of lead concentrations.
• Sample preparation:
  • Non‑halogenated rubbers: dry ashing at 550 °C ± 25 °C (refer ISO 247-1:2018).
  • Halogenated rubbers: acid mineralization (sulfuric + nitric acids), evaporation and subsequent ashing to avoid loss of volatile lead compounds.
• Dissolution and digestion:
  • Ash is boiled with ammonium acetate to dissolve lead; insoluble lead silicates converted using HCl, HNO3 and H2O2.
• Instrumentation:
  • Atomic absorption spectrometer with lead hollow‑cathode lamp; measurement wavelength 283.3 nm.
  • Graphite furnace (electrothermal atomization) may be used for enhanced sensitivity.
• Calibration and quality control:
  • Prepare calibration solutions from certified lead stock and construct a calibration graph; include blank determinations.
  • Standard‑additions method available (Annex A) to reduce detection limits and compensate for matrix effects.
• Reagents and apparatus: Lists acids, ammonium acetate, standard lead solutions, muffle furnace, pipettes, volumetric flasks and other laboratory glassware.

Applications and who uses it

ISO 6101-2:2019 is used by:

• Industrial and independent testing laboratories performing elemental analysis of rubber.
• Quality control teams at rubber manufacturers to monitor lead contamination and compliance.
• Regulatory bodies and product safety assessors verifying lead content in consumer or industrial rubber goods.
• R&D and materials scientists developing formulations or studying metal additives in elastomers.

Practical applications include batch release testing, failure analysis, compliance with chemical safety regulations, and formulation screening where metal contaminants or additives (lead) are of interest.

Related standards

• ISO 247-1:2018 - Rubber - Determination of ash - Combustion method (referenced for ashing).
• ISO 1795 - Sampling of raw rubber.
• ISO 123 - Sampling of rubber latex.
• ISO 648, ISO 1042, ISO 1772 - Laboratory glassware and crucible specifications.

Keywords: ISO 6101-2:2019, lead determination, atomic absorption spectrometry, AAS, rubber testing, lead content in rubber, graphite furnace, standard-additions, sample ashing.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 6101-2
Third edition
2019-11
Rubber — Determination of metal
content by atomic absorption
spectrometry —
Part 2:
Determination of lead content
Caoutchouc — Détermination de la teneur en métal par
spectrométrie d'absorption atomique —
Partie 2: Dosage du plomb
Reference number
©
ISO 2019
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents . 2
6 Apparatus . 3
7 Sampling . 3
8 Procedure. 4
8.1 Test portion . 4
8.2 Preparation of test solution . 4
8.2.1 Destruction of organic matter . 4
8.2.2 Dissolution of inorganic residue . 4
8.3 Preparation of the calibration graph . 5
8.3.1 Preparation of calibration solutions . 5
8.3.2 Spectrometric measurements . 5
8.3.3 Plotting the calibration graph . 5
8.4 Determination . 5
8.4.1 Spectrometric measurements . 5
8.4.2 Dilution. 6
8.5 Blank determination . 6
8.6 Number of determinations . 6
9 Expression of results . 6
10 Test report . 7
Annex A (informative) Method of standard additions . 9
Foreword
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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).
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constitute an endorsement.
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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 www .iso .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 third edition cancels and replaces the second edition (ISO 6101-2:1997), of which it constitutes
a minor revision to update normative references in Clause 2.
A list of all parts in the ISO 6101 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2019 – All rights reserved

INTERNATIONAL STANDARD ISO 6101-2:2019(E)
Rubber — Determination of metal content by atomic
absorption spectrometry —
Part 2:
Determination of lead content
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
determine the applicability of any other restrictions.
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 an atomic absorption spectrometric method for the determination of the lead
content of rubbers.
The method is applicable to raw rubber and rubber products. There is no limit to the concentration
of lead that can be determined. High or low concentrations can be determined, provided that suitable
adjustments are made to the mass of the test portion and/or the concentration of the solutions used.
The use of the standard-additions method might lower the bottom limit of detection.
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 247-1:2018, Rubber — Determination of ash — Part 1: Combustion method
ISO 648, Laboratory glassware — Single-volume pipettes
ISO 1042, 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
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Principle
If the rubber does not contain halogenated compounds, a test portion is directly ashed at 550 °C ± 25 °C
as specified in ISO 247-1:2018, method A. If the rubber contains halogenated compounds, a test portion
is first mineralized with sulfuric and nitric acids, the acids are removed by evaporation, and the portion
is ashed at 550 °C ± 25 °C.
NOTE The presence of even small amounts of halogens can lead to the loss of volatile lead salts during
dry ashing.
The ash obtained is boiled with ammonium acetate solution to dissolve the lead. Insoluble lead silicates,
if present, are converted to chloride by boiling with a mixture of hydrochloric acid, nitric acid and
hydrogen peroxide.
The solution is aspirated into an atomic absorption spectrometer and the absorbance is measured at a
wavelength of 283,3 nm, using a lead hollow-cathode lamp as the lead 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 Sulfuric acid, ρ = 1,84 Mg/m .
5.2 Nitric acid, ρ = 1,40 Mg/m .
5.3 Hydrochloric acid, ρ = 1,18 Mg/m .
5.4 Hydrochloric acid, diluted 1 + 2.
Dilute 1 volume of concentrated hydrochloric acid (5.3) with 2 volumes of water.
5.5 Hydrogen peroxide, 30 % (mass fraction) solution.
5.6 Ammonium acetate, 180 g/dm solution.
5.7 Standard lead stock solution, containing 1 g of Pb per cubic decimetre.
Either use a commercially available standard lead solution, or prepare as follows:
Weigh, to the nearest 0,1 mg, 1 g of metallic lead (purity ≥ 99,95 %) and transfer to a 100 cm beaker
3 3
(6.12). Add 30 cm of water and 20 cm of nitric acid (5.2) and boil on a sand bath (6.10). If the lead is
dissolved, continue boiling until the solution is reduced to about 20 cm or less. No nitrogen oxides
should be observed. Otherwise, add water and continue boiling. Transfer to a 1 000 cm one-mark
volumetric flask (see 6.7) with 1 + 2 hydrochloric acid (5.4) and fill to the mark with 1 + 2 hydrochloric
acid (5.4).
1 cm of this standard stock solution contains 1 mg of Pb.
5.8 Standard lead solution, containing 10 mg of Pb per cubic decimetre.
Using a pipette (6.9), carefully introduce 10 cm of the standard lead stock solution (5.7) into a
1 000 cm one-mark volumetric flask (see 6.7). Dilute to the mark with 1 + 2 hydrochloric acid (5.4),
and mix thoroughly.
Prepare this solution on the day of use.
1 cm of this standard solution contains 10 μg of Pb.
2 © ISO 2019 – All rights reserved

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