ISO 11723:2016

Solid mineral fuels - Determination of arsenic and selenium - Eschka's mixture and hydride generation method

ISO 11723:2016 specifies a method using Eschka's mixture during ashing, extraction of the ash residue with acid, and hydride generation atomic absorption spectrometry or hydride generation atomic fluorescence spectrometry, for the determination of arsenic and selenium in solid mineral fuels.

Combustibles minéraux solides — Dosage de l'arsenic et du sélénium — Mélange d'Eschka et méthode par production d'hydrure

General Information

• Status: Published
• Publication Date: 17-Nov-2016
• ICS: 73.040 - Coals
• Technical Committee: ISO/TC 27/SC 5 - Methods of analysis
• Drafting Committee: ISO/TC 27/SC 5/WG 8 - Major, minor and trace elements in coal and coal residues
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 25-Jun-2025
• Completion Date: 13-Dec-2025

Relations

• Revised: ISO 11723:2025 - Coal and coke - Determination of arsenic and selenium - Eschka's mixture and hydride generation method
• Effective Date: 27-May-2023
• Revises: ISO 11723:2004 - Solid mineral fuels - Determination of arsenic and selenium - Eschka's mixture and hydride generation method
• Effective Date: 21-Nov-2015

Overview

ISO 11723:2016 is an international standard that specifies a precise analytical method for determining arsenic and selenium content in solid mineral fuels. This method combines the use of Eschka’s mixture during ashing with an acid extraction step, followed by quantification through hydride generation atomic absorption spectrometry (AAS) or atomic fluorescence spectrometry (AFS). The standard is essential for ensuring accurate, reproducible measurements of these toxic elements in coal, coke, lignite, and other solid mineral fuels, supporting compliance with environmental and safety regulations.

Key Topics

• Scope and Purpose
  Defines a robust procedure for arsenic and selenium determination that applies to various solid mineral fuels. It also includes optional use of inductively coupled plasma atomic emission spectrometry (ICP-AES) equipped with hydride generation.

• Sample Preparation
  Emphasizes precise sample handling, including moisture equilibration and preparation of a test portion mixed with Eschka’s mixture. Controlled ashing at 800 °C removes organic matter without loss of analytes.

• Reagents and Standards
  Details preparation of essential reagents such as Eschka’s mixture, hydrochloric and nitric acid, potassium iodide, sodium borohydride for hydride generation, and arsenic and selenium stock and working standards. Use of analytical-grade chemicals and Grade 1 pure water is mandatory to ensure accuracy.

• Analytical Procedure
  Covers blank determinations, test solution preparation, calibration standard preparation, and preparation of samples for measurement with specific treatments for arsenic and selenium. Includes careful control of temperature and timing to optimize analyte reduction before measurement.

• Measurement Techniques
  Implements hydride generation coupled with atomic absorption or atomic fluorescence spectrometry for selective determination of arsenic (at 193.7 nm) and selenium (at 196.0 nm). The standard allows flexibility in instrumentation with guidance to follow manufacturers’ instructions for optimal performance.

• Result Expression and Precision
  Specifies calculation methods for reporting results including adjustments for moisture content. Precision criteria such as repeatability and reproducibility are outlined for quality control and validation.

Applications

ISO 11723:2016 provides a vital analytical reference for:

• Environmental Monitoring
  Measuring arsenic and selenium in coal and related materials to assess potential environmental contamination during mining, processing, or combustion.

• Fuel Quality Control
  Ensuring compliance with regulatory limits for hazardous elements in solid mineral fuels used in power generation or industry.

• Research and Development
  Facilitating studies related to trace element behavior in solid fuels, improving fuel processing techniques, and developing cleaner combustion technologies.

• Regulatory Compliance
  Assisting laboratories and industries in meeting national and international emission standards by accurately determining arsenic and selenium contents.

Related Standards

ISO 11723:2016 references and complements several other ISO standards critical for solid mineral fuel analysis:

• ISO 5069-2 – Sampling methods and preparation of coal and lignite for analysis.
• ISO 5068-2 – Moisture determination in brown coals and lignites, relevant for correcting results.
• ISO 11722 – Moisture content determination in hard coal samples.
• ISO 687 – Moisture determination in coke samples for accurate compositional data.
• ISO 13909-4 & ISO 13909-6 – Mechanical sampling and preparation of coal and coke test samples.
• ISO 3696 – Quality requirements for laboratory water ensuring chemical purity essential for reagent preparation.

These interconnected standards provide a comprehensive framework for sample preparation, moisture analysis, and overall quality assurance in mineral fuel testing.

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Keywords: ISO 11723:2016, arsenic determination, selenium analysis, solid mineral fuels, Eschka’s mixture, hydride generation, atomic absorption spectrometry, atomic fluorescence spectrometry, coal quality control, fuel contamination analysis, analytical chemistry standard, environmental monitoring.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 11723
Second edition
2016-11-15
Solid mineral fuels — Determination
of arsenic and selenium — Eschka’s
mixture and hydride generation
method
Combustibles minéraux solides — Dosage de l’arsenic et du sélénium
— Mélange d’Eschka et méthode par production d’hydrure
Reference number
©
ISO 2016
© ISO 2016, Published in Switzerland
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ii © ISO 2016 – All rights reserved

Contents Page
Foreword .iv
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 Blank determination . 3
8.2 Preparation of test solution . 3
8.3 Preparation of calibration standards . 4
8.4 Preparation for measurement . 4
8.4.1 General. 4
8.4.2 Arsenic . 4
8.4.3 Selenium . . 4
9 Measurement by atomic absorption or atomic fluorescence spectrometry after
hydride generation . 4
10 Expression of results . 5
11 Precision . 5
11.1 Repeatability . 5
11.2 Reproducibility critical difference . 6
12 Test report . 6
Foreword
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different types of ISO documents should be noted. This document was drafted in accordance with the
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Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.
The committee responsible for this document is ISO/TC 27, Solid minerals fuels, Subcommittee SC 5,
Methods of analysis.
This second edition cancels and replaces the first edition (ISO 11723:2004), which has been technically
revised. This document incorporates changes related to dated references and other minor items
following its systematic review.
iv © ISO 2016 – All rights reserved

INTERNATIONAL STANDARD ISO 11723:2016(E)
Solid mineral fuels — Determination of arsenic and
selenium — Eschka’s mixture and hydride generation
method
1 Scope
This document specifies a method using Eschka’s mixture during ashing, extraction of the ash residue
with acid, and hydride generation atomic absorption spectrometry or hydride generation atomic
fluorescence spectrometry, for the determination of arsenic and selenium in solid mineral fuels.
NOTE The method is also applicable to the determination of the analytes by hydride generation inductively
coupled plasma atomic emission spectrometry.
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, Solid mineral fuels — Coke — Determination of moisture in the general analysis test sample
ISO 1170, Coal and coke — Calculation of analyses to different bases
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 5068-2, Brown coals and lignites — Determination of moisture content — Part 2: Indirect gravimetric
method for moisture in the analysis sample
ISO 5069-2, Brown coals and lignites — Principles of sampling — Part 2: Sample preparation for
determination of moisture content and for general analysis
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 13909-6, Hard coal and coke — Mechanical sampling — Part 6: Coke — Preparation of test samples
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:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
4 Principle
A known mass of the sample is ignited in intimate contact with Eschka’s mixture in an oxidizing
atmosphere at 800 °C to remove the organic matter. The residue is then extracted with hydrochloric
acid and the analytes determined by hydride generation atomic absorption spectrometry or hydride
generation atomic fluorescence spectrometry.
5 Reagents
WARNING — Care must be exercised when handling reagents, many of which are toxic and
corrosive.
During the analysis, unless otherwise stated, use only reagents of recognized analytical reagent grade
and water conforming to Grade 1 of ISO 3696.
5.1 Eschka’s mixture, composed of two parts by mass of light magnesium oxide and one part by mass
of anhydrous sodium carbonate.
5.2 Hydrochloric acid (ρ 1,19 g/ml).
5.3 Nitric acid (ρ 1,42 g/ml).
5.4 Potassium iodide solution, 500 g/l. Dissolve 50 g of analytical reagent (AR) grade KI in distilled
water and adjust the volume to 100 ml (for determination of As).
5.5 Sodium borohydride solution. Weigh 1,50 g of sodium borohydride (NaBH ) and 0,4 g of sodium
hydroxide (N
...