ISO 29541:2025

Coal and coke - Determination of total carbon, hydrogen and nitrogen - Instrumental method

This document specifies a method for the determination of total carbon, hydrogen and nitrogen in coal and coke by instrumental methods. NOTE This document has been validated for coal only, in accordance with the principles of ISO 5725-1. The suite of samples used in the interlaboratory study (ILS) to determine the precision data did not include coke and therefore there is insufficient data to state precision limits for coke.

Combustibles minéraux solides — Dosage du carbone, de l'hydrogène et de l'azote totaux — Méthode instrumentale

General Information

• Status: Published
• Publication Date: 03-Feb-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-Feb-2025
• Due Date: 20-May-2025
• Completion Date: 04-Feb-2025

Relations

• Revises: ISO 29541:2010 - Solid mineral fuels - Determination of total carbon, hydrogen and nitrogen content - Instrumental method
• Effective Date: 27-May-2023

Overview

ISO 29541:2025 - "Coal and coke - Determination of total carbon, hydrogen and nitrogen - Instrumental method" specifies an instrumental combustion procedure for the concurrent determination of total carbon (C), hydrogen (H) and nitrogen (N) in coal and coke. The method converts sample C, H and N to gaseous products (CO2, H2O, N/NOx) by combustion in oxygen, removes interfering species, reduces NOx to N2 and quantifies the gases by instrumental gas analysis. Note: the method and its precision data were validated for coal only; precision limits for coke are not established due to insufficient interlaboratory data.

Key topics and requirements

• Principle: Single-run combustion with gas analysis for CO2, H2O and N (after NOx reduction).
• Instrument and sample: Analytical instrument with furnace, gas-handling and detectors capable of analysing test portions of 6 mg or greater; balance resolution appropriate to test mass.
• Sample preparation: General analysis test sample ground to a nominal top size of 212 µm, moisture equilibrated with laboratory atmosphere and thoroughly mixed.
• Reagents and calibration materials: Carrier gas (e.g., helium), oxygen and certified calibration materials (examples include EDTA, phenylalanine, acetanilide, BBOT). Coal must not be used for calibration because composition can change with storage.
• Procedure essentials:
  • Instrument set-up and leak checks
  • Daily blank analyses to monitor background C/H/N
  • Conditioning and stability checks (discarding initial runs)
  • Calibration and verification using independent calibration material
  • Regular verification during batches (preferably every ten samples); samples analysed in duplicate
• Acceptance limits for calibration verification:
  • Carbon: ±0.2% (relative)
  • Hydrogen: ±0.5% (relative)
  • Nitrogen: ±1% (relative)
• Quality/precision: Repeatability and reproducibility limits are provided in Clause 10 (updated in this edition); the validation follows ISO 5725-1 principles.
• Safety: Method involves hazardous operations and materials - users must follow appropriate safety practices.

Applications and users

ISO 29541:2025 is used where reliable total C, H and N measurements are required:

• Coal and coke quality control laboratories
• Power generation and utilities (combustion calculations, fuel characterization)
• Mining companies and coke producers (product specification)
• Environmental and emissions modelling (fuel carbon accounting)
• Research institutions and instrument manufacturers (method development, calibration) The standard supports accurate carbon accounting, combustion performance assessment and compliance with fuel specification requirements.

Related standards

• ISO 5725-1 (method validation/precision principles)
• ISO 13909-4, ISO 18283 (sample preparation and sampling)
• ISO 11722, ISO 687, ISO 5068-2 (moisture determination methods)

Keywords: ISO 29541:2025, coal and coke analysis, total carbon hydrogen nitrogen, instrumental combustion method, calibration, sample preparation, coal analysis, coke analysis, precision limits.

Standards Content (Sample)

International
Standard
ISO 29541
Second edition
Coal and coke — Determination of
2025-02
total carbon, hydrogen and nitrogen
— Instrumental method
Combustibles minéraux solides — Dosage du carbone, de
l'hydrogène et de l'azote totaux — Méthode instrumentale
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
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or ISO’s member body in the country of the requester.
ISO copyright office
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 2
6 Apparatus . 3
7 Preparation of the test sample. 3
8 Procedure . 3
8.1 Instrument set-up .3
8.2 Blank analyses .3
8.3 Conditioning and instrument stability check .3
8.4 Calibration .3
8.5 Verification of calibration .4
8.6 Analysis of test samples .4
9 Expression of results . 4
10 Precision . 5
10.1 Repeatability limit .5
10.2 Reproducibility limit .5
11 Test report . 6
Annex A (normative) Recommendations for calibration . 7
Bibliography .10

iii
Foreword
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bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
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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).
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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 second edition cancels and replaces the first edition (ISO 29541:2010), which has been technically
revised.
The main changes are as follows:
— the repeatability limits have been updated.
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
Introduction
The reliable determination of total carbon, hydrogen and nitrogen is important for engineering calculations
applied to the combustion of coal. The precise and accurate determination of the mass fraction of carbon in
coal is essential for carbon accounting purposes.

v
International Standard ISO 29541:2025(en)
Coal and coke — Determination of total carbon, hydrogen and
nitrogen — Instrumental method
WARNING — The use of this document can involve hazardous materials, operations and equipment. It
does not purport to address all of the safety problems associated with its use. It is the responsibility
of the user of this document to establish appropriate safety and health practices and determine the
applicability of regulatory limitations prior to use.
1 Scope
This document specifies a method for the determination of total carbon, hydrogen and nitrogen in coal and
coke by instrumental methods.
NOTE This document has been validated for coal only, in accordance with the principles of ISO 5725-1. The suite
of samples used in the interlaboratory study (ILS) to determine the precision data did not include coke and therefore
there is insufficient data to state precision limits for coke.
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 687, Coke — Determination of moisture in the general analysis test sample
ISO 5068-2, Brown coals and lignites — Determination of moisture content — 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, Hard coal and coke — Mechanical sampling — Part 4: Coal — Preparation of test samples
ISO 18283, Coal and coke — Manual sampling
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Principle
Carbon, hydrogen and nitrogen are determined concurrently in a single instrumental procedure. The
quantitative conversion of the carbon, hydrogen and nitrogen into their corresponding gases (CO , H O,
2 2
N /NO ) occurs during combustion of the sample at an elevated temperature in an atmosphere of oxygen.
2 x
Combustion products which can interfere with the subsequent gas analysis are removed. Oxides of nitrogen
(NO ) produced during the combustion are reduced to N before detection. The carbon dioxide, water vapour
x 2
and elemental nitrogen in the gas stream are then determined quantitatively by appropriate instrumental
gas analysis procedures.
5 Reagents
Unless otherwise specified, all reagents shall be of analytical reagent grade.
5.1 Carrier gas, helium or other suitable gas as specified by the instrument manufacturer.
5.2 Oxygen, as specified by the instrument manufacturer.
5.3 Additional reagents, of types and qualities specified by the instrument manufacturer.
5.4 Calibration materials, see Table 1.
Table 1 — Examples of suitable calibration materials
Stoichiometric mass fractions
%
Name Formula
Carbon Hydrogen Nitrogen
EDTA
C H N O 41,1 5,5 9,6
10 16 2 8
(ethylene diamine tetra-acetic acid)
Phenylalanine C H NO 65,4 6,7 8,5
9 11 2
Acetanilide C H NO 71,1 6,7 10,4
8 9
BBOT (CAS-No 7128-64-5)
C H N O S 72,5 6,1 6,5
26 26 2 2
2,5-bis (5′-tert-butyl-2-benzoxazolyl) thiophene
If these materials are accompanied by a traceable certificate of analysis that includes the uncertainty of the
assigned carbon, hydrogen and nitrogen values, then use the certificate values for calibration purposes. It
is recommended that the relative expanded uncertainty for these materials be no more than 0,2 % for C,
0,5 % for H, and 1 % for N. Assuming k = 2, that the relative standard uncertainty be no more than 0,1 % for
C, 0,25 % for H, and 0,5 % for N.
If pure compounds (> 99,5 % purity with stated uncertainty) are available, use the stoichiometric values
multiplied by the stated purity. Uncertainty specifications similar to those stated above are recommended.
Store these substances in a desiccator under conditions that maintain the compounds in a dry state.
Table 1 lists those pure substances that were included in the interlaboratory study (ILS) to determine the
calibration requirements and precision of this document. The ILS indicated benzoic acid is not suitable for
calibration. Pure substances other than those listed in Table 1 can be used for calibration provided the
substances have a documented purity and uncertainty and meet the purity and calibration requirements
of this document. Uncertainty specifications similar to those stated above are recommended for those
substances.
5.5 Reference materials
Reference material coal(s) with a certified composition and uncertainty for carbon, hydrogen and nitrogen
may be used as a check to monitor changes in instrument response, which can be affected by constituents
not present in the calibration materials, and to verify the acceptability of nitrogen results. Alternatively,
coal of a known composition can also be used as a check sample. As the bulk composition of coal can change
during storage, coals shall not be used for calibration.

6 Apparatus
6.1 Analytical instrument, consisting of a furnace, gas handling and detection system capable of
analysing a test portion of 6 mg or greater.
6.2 Balance, stand-alone or integrated with the instrument, with a resolution of at least 0,1 % of the mass
of the test portion.
7 Preparation of the test sample
The sample shall be the general analysis test sample prepared to a nominal top size of 212 µm in accordance
to procedures described in ISO 13909-4 for coal or ISO 18283 for coke.
Ensure that the moisture of the sample is in equilibrium with the laboratory atmosphere, exposing it, if
necessary, in a thin layer for the minimum time required to achieve equilibrium.
Before commencing the determination, thoroughly mix the equilibrated test sample for at least 1 min,
preferably by mechanical means.
The moisture mass fraction of each test sample and the reference material shall be determined in accordance
with ISO 11722, ISO 687 or ISO 5068-2 as appropriate.
8 Procedure
8.1 Instrument set-up
Verify that all instrument operation parameters meet the specifications in the instrument operating
manual. Verify the condition and quantity of all chemicals currently in use in the instrument to ensure they
are satisfactory for the number of samples to be analysed. Prior to any analysis, check for, and if necessary
correct, any leaks in the combustion system and carrier gas system.
8.2 Blank analyses
Perform blank analys
...