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International
Standard
ISO 24181-1
First edition
Rare earth — Determination of non-
2024-08
rare earth impurities in individual
rare earth metals and their oxides
— ICP-AES —
Part 1:
Analysis of Al, Ca, Mg, Fe and Si
Terres rares — Détermination des impuretés de terres non rares
dans les métaux de terres rares individuels et leurs oxydes —
ICP-AES —
Partie 1: Analyse de Al, Ca, Mg, Fe et Si
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 3
5 Reagent . 4
6 Apparatus . 4
6.1 Volumetric glassware .4
6.2 Inductively coupled plasma atomic emission spectrometer .4
6.2.1 General .4
6.2.2 Line spectra selection .4
7 Procedure . 5
7.1 Weighing the test portion .5
7.2 Sample preparation .6
7.3 Preparation of calibration solutions .6
7.4 Measurements . .7
7.4.1 Instrument set-up .7
7.4.2 Measurement of the calibration solution and calibration curve construction .7
7.4.3 Measurement of the test solution .7
8 Calculation and expression of results . 7
8.1 Method of calculation .7
8.2 Precision . . .8
8.2.1 Interlaboratory test .8
8.2.2 Statistical analysis .8
9 Test report . 8
Annex A (informative) Interlaboratory test results . 9
Annex B (informative) Regression formulae of precision . 10
Bibliography .11
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,
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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
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This document was prepared by Technical Committee ISO/TC 298, Rare earth.
A list of all parts in the ISO 24181 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
Introduction
Atomic spectroscopy has been recognised as the most common technique for trace elemental determinations.
Although atomic absorption spectroscopy is limited to determination of one element at a time, many elements
are analysed routinely at the same time by inductively coupled plasma atomic emission spectroscopy
(ICP-AES), which utilises the inductively coupled plasma (ICP) as an excitation source for atomic emission
spectrometry (AES). Several thousands of these instruments are in routine use throughout the world.
ICP-AES is the most common technique for trace elemental determinations, particularly for the analysis of
impurities. This method has been demonstrated to feature a linear response over a wide dynamic range,
a low chemical interference/matrix effect, good stability and good reproducibility. It demonstrates a low
detection limit and various sample introduction techniques are available for different sample analysis
demands.
In rare earth metals and oxides, during processing ores of rare earth elements, Aluminum(Al), calcium(Ca),
magnesium(Mg), iron(Fe) and silicon(Si) are contained as impurities. ICP-AES is well-suited for the
quantification of non-rare earth impurities in a matrix containing rare earth elements. Additionally, the ICP-
AES technique also offers high resolution for rare earth elements as rare earth elements exhibits line-rich
emission spectra.
This document provides a guide for chemical analysis of materials for producers, consumers, and traders in
the field of rare-earth metals and their oxides. This document is anticipated to reduce discrepancies caused
by inconsistencies in the analytical procedures used when working with rare earth metals and their oxides.
v
International Standard ISO 24181-1:2024(en)
Rare earth — Determination of non-rare earth impurities in
individual rare earth metals and their oxides — ICP-AES —
Part 1:
Analysis of Al, Ca, Mg, Fe and Si
WARNING — The use of this document can involve hazardous chemicals, materials, operations and
equipment. This document does not purport to address any safety problems associated with its
use. It is the responsibility of the user of this document to establish appropriate safety and health
practices and to determine the applicability of regulatory limitations before use (e.g. according to
ISO 15202-2 and ISO 15202-3).
1 Scope
This document describes procedures for the determination of non-rare earth impurities in individual rare
earth metals and their oxides through the use of inductively coupled plasma atomic emission spectroscopy
(ICP-AES). Magnesium (Mg), aluminum (Al), silicon (Si), calcium (Ca) and iron (Fe) are included as non-
rare earth impurity elements, and the measurement ranges for each impurity element are specified. The
applicable measurement range (mass fraction %) of magnesium, aluminum, silicon and calcium is from
0,001 to 0,2, and that of iron is from 0,001 to 0,5. The verified measurement ranges in the interlaboratory
tests are described later in this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content dictates
requirements or specifications 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 648, Laboratory glassware — Single-volume pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 11885, Water quality — Determination of selected elements by inductively coupled plasma optical emission
spectrometry (ICP-OES)
ISO 22444-1, Rare earth — Vocabulary — Part 1: Minerals, oxides and other compounds
ISO 22444-2, Rare earth — Vocabulary — Part 2: Metals and their alloys
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 22444-1, ISO 22444-2 and the
following apply.
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/
3.1
inductively coupled plasma
ICP
high-temperature (8 000 K to 10 000 K) discharge of energy generated in a ionized gas, usually argon,
produced by a radio frequency controlled varying magnetic field, originating from an AC current flowing in
a water-cooled copper coil or in an induction coil which surrounds tubes through which the gas flows
3.2
inductively coupled plasma-atomic emission spectroscopy
ICP-AES
type of atomic spectroscopy in which
...