ISO 15238:2025

Coal - Determination of total cadmium

This document specifies a procedure for the determination of the total cadmium mass fraction of coal.

Charbon — Dosage du cadmium total

General Information

• Status: Published
• Publication Date: 03-Jul-2025
• ICS: 73.040 - Coals
• ICS: 75.160.10 - Solid fuels
• Technical Committee: ISO/TC 27/SC 5 - Methods of analysis
• Drafting Committee: ISO/TC 27/SC 5 - Methods of analysis
• Current Stage: 6060 - International Standard published
• Start Date: 04-Jul-2025
• Due Date: 20-May-2026
• Completion Date: 04-Jul-2025

Relations

• Revises: ISO 15238:2016 - Solid mineral fuels - Determination of total cadmium content of coal
• Effective Date: 27-May-2023

Overview

ISO 15238:2025 specifies a laboratory procedure for the determination of the total cadmium mass fraction in coal. The method combines controlled ashing of a representative coal sample with dissolution of the ash and quantification by graphite-furnace atomic absorption spectroscopy (GFAAS/AAS). This third edition updates normative references and refines calculation formulae; it is intended for routine monitoring, quality control and regulatory assessment of cadmium in coal.

Key Topics

• Principle: Coal is ashed, the ash is dissolved (aqua regia + hydrofluoric acid), complexed with boric acid and analysed by graphite-furnace AAS for cadmium quantification.
• Sample preparation: Prepare representative test samples in accordance with ISO 13909-4 or ISO 18283 and equilibrate moisture before analysis.
• Ashing conditions: Place samples in silica or platinum crucibles and raise to (450 ± 10) °C, maintaining that temperature for at least 2 h (minimum overall ashing time 3 h; up to 18 h allowed).
• Reagents and standards: Use analytical-grade reagents (Grade 1 water per ISO 3696). Key reagents include aqua regia, concentrated hydrofluoric acid, saturated boric acid and certified cadmium standard solutions (stock and working solutions).
• Instrumental analysis: Calibration uses matrix-matched standards (examples: 0.0, 1.0, 2.5 and 5.0 µg/l) and instrument verification with certified reference materials. No additional matrix modifier is required when appropriate furnace parameters are used.
• Quality assurance: Prepare blank solutions, perform duplicate determinations and record the mean result to the nearest 5 ng/g on the "as analysed" basis.

Applications

• Routine environmental and occupational monitoring of cadmium in coal feedstocks and products.
• Laboratory quality control for coal analysis and certification programs.
• Supporting regulatory compliance and risk assessments where cadmium reporting is required.

Practical notes from the standard:

• Exercise caution handling corrosive and toxic reagents (HF is highly hazardous).
• Microwave or pressurized-vessel dissolution of ash may be used as an alternative if quantitative cadmium recovery is demonstrated.
• The method has not been validated for coals that spontaneously ignite; users must validate performance before applying the procedure to such samples.

Related Standards

• ISO 3696 - Water for analytical laboratory use
• ISO 13909-4 - Coal sampling and test-sample preparation
• ISO 18283 - Manual sampling of coal and coke
• ISO 5068-2 and ISO 11722 - Moisture determination methods

This standard is prepared by ISO/TC 27/SC 5 (Coal and coke methods of analysis) and replaces ISO 15238:2016. For implementation, consult the full ISO 15238:2025 document and national standards body guidance.

Standards Content (Sample)

International
Standard
ISO 15238
Third edition
Coal — Determination of total
2025-07
cadmium
Charbon — Dosage du cadmium total
Reference number
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 1
6 Apparatus . 2
7 Preparation of sample . 2
8 Procedure . 3
8.1 Ashing of coal sample .3
8.2 Preparation of test solution .3
8.3 Preparation of blank solution . .3
8.4 Graphite-furnace atomic absorption analysis .3
8.4.1 Calibration . . .3
8.4.2 Measurement of standards .3
8.4.3 Measurement of test solution . .4
8.4.4 Measurement of blank solution .4
9 Expression of results . 4
9.1 Ash mass fraction . .4
9.2 Cadmium mass fraction .4
10 Precision . 5
10.1 Repeatability limit .5
10.2 Reproducibility critical difference .5
11 Test report . 5
Bibliography . 6

iii
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and 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 27, Coal and coke, Subcommittee SC 5, Methods
of analysis.
This third edition cancels and replaces the second edition (ISO 15238:2016), which has been technically
revised.
The main changes are as follows:
— the normative references have been updated;
— Formulae (1) and (2) have been modified.
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
International Standard ISO 15238:2025(en)
Coal — Determination of total cadmium
1 Scope
This document specifies a procedure for the determination of the total cadmium mass fraction of coal.
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 3696, Water for analytical laboratory use — Specification and test methods
ISO 5068-2, Brown coals and lignites — Determination of moisture — Part 2: Indirect gravimetric method for
moisture in the analysis sample
ISO 11722, Solid mineral fuels — Hard coal — Determination of moisture in the general analysis test sample by
drying in nitrogen
ISO 13909-4, Coal and coke — Mechanical sampling — Part 4: Preparation of test samples of coal
ISO 18283, Coal and coke — Manual sampling
3 Terms and definitions
No terms and definitions are listed in this document.
...