ISO 23201:2015

INTERNATIONAL ISO
STANDARD 23201
First edition
2015-11-15
Aluminium oxide primarily used
for production of aluminium —
Determination of trace elements
— Wavelength dispersive X-ray
fluorescence spectrometric method
Oxyde d’aluminium utilisé pour la production d’aluminium —
Détermination d’éléments traces — Spectrométrie de fluorescence des
rayons X par dispersion en longueur d’onde
Reference number
ISO 23201:2015(E)
©
ISO 2015

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ISO 23201:2015(E)

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ISO 23201:2015(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Principle . 2
4 Reagents and materials . 2
5 Apparatus . 3
6 Sampling and samples . 5
7 Procedure. 5
7.1 General . 5
7.2 Preparation of calibration specimens . 6
7.2.1 Determination of loss of mass on fusion of flux and flux correction . 6
7.2.2 Preparation of intermediate calibration glass (ICG) . 6
7.2.3 Preparation of the synthetic calibration disk (SCD) . 7
7.2.4 Preparation of the blank calibration discs . 9
7.3 Preparation of the sample discs . 9
7.4 X-ray fluorescence measurement .10
7.4.1 General instrumental conditions .10
7.4.2 Guidelines for instrument optimization .11
7.4.3 Sample loading .11
7.4.4 Monitor disc: correction for instrumental drift .11
7.4.5 Measurements for calibration .12
7.4.6 Measurement of test discs .13
8 Calculations.13
8.1 Calculation of net intensity .13
8.2 Comparison of duplicate measurements for the Al O blanks and Synthetic
2 3
Calibration Discs (SCDs) .14
8.2.1 SCDs criteria for the acceptability of duplicate measurements .14
8.2.2 Al O blanks criteria for the acceptability of duplicate measurement .14
2 3
8.3 Drift correction of measured intensities.15
8.4 Calculation of the calibration parameters .15
9 Consistency checks and reporting results .16
10 Precision .16
11 Accuracy .17
12 Quality assurance and control.17
13 Test report .17
Annex A (informative) Contamination issues and care of platinum ware .19
Annex B (normative) Example of instrument optimization .21
Annex C (informative) Calculation of reagent masses for different sample/flux
combinations and synthetic calibration discs when omitting some elements .25
Annex D (informative) Preparation of monitor disc .27
Annex E (informative) Interlaboratory test program analysis of NIST 699 and ASCRM 27
smelter grade alumina, certified reference materials .29
Annex F (informative) Comments on flux purity .31
Bibliography .32
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ISO 23201:2015(E)

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 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).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 226, Materials for the production of primary
aluminium.
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ISO 23201:2015(E)

Introduction
This International Standard is based on Australian Standard AS 2879.7–1997, Alumina — Determination
of trace elements — Wavelength dispersive X-ray fluorescence spectrometric method, developed by the
Standards Australia Committee on Alumina and Materials used in Aluminium Production to provide an
XRF method for the analysis of alumina.
The objective of this International Standard is to provide those responsible for the analysis of smelting-
grade alumina with a standardized, validated procedure that will ensure the integrity of the analysis.
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INTERNATIONAL STANDARD ISO 23201:2015(E)
Aluminium oxide primarily used for production of
aluminium — Determination of trace elements —
Wavelength dispersive X-ray fluorescence spectrometric
method
1 Scope
This International Standard sets out a wavelength dispersive X-ray fluorescence spectrometric method
for the analysis of aluminium oxide for trace amounts of any or all of the following elements: sodium,
silicon, iron, calcium, titanium, phosphorus, vanadium, zinc, manganese, gallium, potassium, copper,
chromium and nickel. These elements are expressed as the oxides Na O, SiO , Fe O , CaO, TiO , P O ,
2 2 2 3 2 2 5
V O , ZnO, MnO, Ga O , K O, CuO, Cr O and NiO on an un-dried sample basis.
2 5 2 3 2 2 3,
The method is applicable to smelting-grade aluminium oxide. The concentration range covered for each
of the components is given in Table 1.
Table 1 — Applicable concentration range
Concentration range
Component
%
Na O 0,10 to 1,00
2
SiO 0,003 to 0,05
2
Fe O 0,003 to 0,05
2 3
CaO 0,003 to 0,10
TiO 0,000 5 to 0,010
2
P O 0,000 5 to 0,050
2 5
V O 0,000 5 to 0,010
2 5
ZnO 0,000 5 to 0,010
MnO 0,000 5 to 0,010
Ga O 0,000 5 to 0,020
2 3
K2O 0,000 5 to 0,010
CuO 0,000 5 to 0,010
Cr O 0,000 5 to 0,010
2 3
NiO 0,000 5 to 0,010
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
AS 2563, Wavelength dispersive X-ray fluorescence spectrometers — Determination of precision
AS 2706, Numeric values — Rounding and interpretation of limiting values
AS 4538.1-1999 (R2013), Guide to the sampling of alumina — Sampling procedures
AS 4538.2-2000 (R2013), Guide to the sampling of alumina — Preparation of samples
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ISO 23201:2015(E)

3 Principle
A portion of the aluminium oxide test sample is incorporated, via fusion, into a borate glass disc using a
casting technique. X-ray fluorescence measurements are made on this disc.
Calibration is carried out using synthetic standards prepared from pure chemicals using a two-point
regression. Matrix corrections may be employed but, because of the low levels at which the analytes are
present in the Al O matrix, will have negligible effect within the scope of the method.
2 3
Intensity measurements are corrected for spectrometer drift.
A certified reference material, (see Annex E) is used to verify the calibration.
4 Reagents and materials
4.1 Flux, mixture of 12 parts lithium tetraborate to 22 parts lithium metaborate, pre-fused.
This flux is available commercially. Flux will absorb atmospheric moisture when exposed to air.
Minimize water uptake by storing flux in an airtight container.
See Annex F for comments on flux purity.
4.2 Aluminium oxide (Al O ), high purity, nominally 99,999 % Al O .
2 3 2 3
Prepared by heating to 1 200 °C± 25 °C for 2 h and cooling in a desiccator.
To ensure the high purity Al O is not contaminated with analyte elements, analyse it before use by
2 3
preparing a disc made from the aluminium oxide (referred to as a “blank disc”) and measuring net
intensities for each analyte element.
The method for the measurement of blank discs is given in 7.4.5. If a number of differently sourced high
purity aluminium oxides are tested select the one with the lowest countrates for impurities for use
in calibration and blank discs. A.3 gives instructions for reducing silica contamination in high purity
aluminium oxide and may be employed if required.
4.3 Sodium tetraborate (Na B O ), nominally 99,99 % Na B O .
2 4 7 2 4 7
Prepared by heating to 650 °C ± 25 °C for 4 h minimum and cooling in a desiccator.
4.4 Silicon dioxide (SiO ), nominally 99,9 % SiO .
2 2
Prepared by heating to 1 200 °C ± 25 °C for 2 h and cooling in a desiccator.
4.5 Iron(III) oxide (Fe O ), nominally 99,9 % Fe O .
2 3 2 3
Prepared by heating to 1 000 °C ± 25 °C for a minimum of 1 h and cooling in a desiccator.
4.6 Calcium carbonate (CaCO ), nominally 99,9 % CaCO .
3 3
Prepared by heating to 105 °C ± 5 °C for 1 h and cooling in a desiccator.
4.7 Titanium dioxide (TiO ), nominally 99,9 % TiO .
2 2
Prepared by heating to 1 000 °C ± 25 °C for a minimum of 1 h and cooling in a desiccator.
4.8 Ammonium dihydrogen orthophosphate (NH H PO ), nominally 99,9 % NH H PO .
4 2 4 4 2 4
Prepared by heating to 105 °C ± 5 °C for 1 h and cooling in a desiccator.
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ISO 23201:2015(E)

4.9 Vanadium pentoxide (V O ), nominally 99,9 % V O .
2 5 2 5
Prepared by heating to 600 °C ± 25 °C for 1 h and cooling in a desiccator.
4.10 Zinc oxide (ZnO), nominally 99,9 % ZnO.
Prepared by heating to 1 000 °C ± 25 °C for a minimum of 1 h and cooling in a desiccator.
4.11 Manganese oxide (Mn O ), nominally 99,9 % pure.
3 4
Heat manganese dioxide (99,9 % pure, MnO ) for 24 h at 1 000 °C ± 25 °C in a platinum crucible and cool
2
in a dessicator. Crush the resultant lumpy material to a fine powder. The product material is Mn O .
3 4
4.12 Gallium oxide (Ga O ), nominally 99,9 % Ga O .
2 3 2 3
Prepared by heating to 1 000 °C ± 25 °C for a minimum of 1 h and cooling in a desiccator.
4.13 Potassium carbonate (K CO ), nominally 99,9 % K CO .
2 3 2 3
Prepared by heating to 600 °C ± 25 °C for a minimum of 2 h and cooling in a desiccator.
4.14 Copper oxide (CuO), nominally 99,9 % CuO.
Prepared by heating to 1 000 °C ± 25 °C for a minimum of 1 h and cooling in a desiccator.
4.15 Chromium(III) oxide (Cr O ), nominally 99,9 % Cr O .
2 3 2 3
Prepared by heating to 1 000 °C ± 25 °C for a minimum of 1 h and cooling in a desiccator.
4.16 Nickel(II) oxide (NiO), nominally 99,9 % NiO.
Prepared by heating to 1 000 °C ± 25 °C for a minimum of 1 h and cooling in a desiccator.
4.17 Certified Reference Material (CRM), one or both of the alumina materials NIST699 and ASCRM027.
Prepared by heating to 300 °C ± 10 °C for a minimum of 2 h and cooling in a desiccator. Details for
NIST699 can be found at www.nist.gov. A test report for ASCRM027 is available from SAI-Global, www.
saiglobal.com, details of availability can be found within this International Standard.
5 Apparatus
5.1 Platinum crucible, non-wetting, platinum-alloy with a platinum lid and having a capacity
compatible with the bead requirements.
Typical crucibles have a volume of 25 mL to 40 mL.
Crucibles shall be free of all elements to be determined.
NOTE Silica has been found to be a common contaminant of platinum metal alloys, and a suggested method
for cleaning platinum ware to remove silica is given in A.2.
5.2 Desiccator, provided with an effective, non-contaminating desiccant.
All heat treated reagents (4.2 to 4.17) shall be stored in a desiccator.
NOTE Pelletized molecular sieves and phosphorous pentoxide have been found to be satisfactory desiccants.
Silica gel is not suitable.
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ISO 23201:2015(E)

5.3 Electric furnace, fitted with an automatic temperature controller and capable of maintaining a
temperature of 1 200 °C ± 25 °C.
5.4 Platinum mould, non-wetting, platinum or platinum-alloy, circular-shaped of the type
shown in Figure 1 and with dimensions compatible with sample holders employed in the particular
spectrometer used.
An example of a 35 mm mould is given in Figure 1.
The surfaces of moulds shall be free of all elements to be determined, flat and polished to a mirror finish.
Dimensions in mm (not in scale)
35
2
6
32
Figure 1 — Drawing of platinum/5 % gold mould
NOTE Silica has been found to be a common contaminant, and a suggested method for cleaning platinum
ware and to remove silica is given in A.2.
5.5 X-ray fluorescence spectrometer, wavelength dispersive, vacuum path X-ray fluorescence
spectrometer, provided that the performance of the instrument has been verified and found to comply
with the manufacture’s specifications or the performance requirements given in AS 2563, “Wavelength
dispersive X — ray fluorescence spectrometers — Determination of precision.”
5.6 Vibratory mill, having grinding components that do not contaminate the intermediate calibration
glass (ICG) with analyte elements.
Take care to ensure that contaminants from the grinding equipment do not affect the analysis.
NOTE Alumina, tungsten carbide and zirconia grinding components have been found to be satisfactory.
5.7 Fusion equipment, an electric furnace capable of maintaining a temperature of 1 100 °C ± 25 °C.
A flat, level heat sink is required to cool hot charged moulds. Using both an aluminium and ceramic
heat sink is effective, where initial cooling is achieved on the ceramic heat sink and quicker cooling to
ambient temperature is achieved on the aluminium heat sink.
Alternatively, commercially available automatic fusion machines may be used since the development of
modern automated fusion equipment has made bead preparation faster and significantly less operator-
dependent. Most of these machines use similar sized crucibles and moulds to those described in the
manual method and simulate the action required to ensure complete dissolution of the sample in the
molten flux. The use of these devices to prepare fused beads is acceptable as long as the agitation
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ISO 23201:2015(E)

provided is sufficient to ensure complete dissolution of the samples and that it can be demonstrated
that the results so generated achieve the accuracy and precision criteria outlined in Clauses 11 and 12.
WARNING — Warning: certain flame fusion devices have been found to reduce reported Fe O
2 3
levels by up to 0,002 % due to reduction and subsequent alloying with the Pt crucible. Other
elements may also be affected. For burner type fusion devices an oxidizing flame shall be used.
5.8 Balance, analytical balance capable of weighing up to 100 g, to the nearest 0,1 mg.
5.9 Platinum tipped stainless steel tongs, for transferring crucibles (5.1) and their lids in and out of
the furnace (5.3) and, where applicable, fusion equipment (5.7) of a length and construction suitable for
safely performing this task.
A heat shield fitted to the front of the tongs’ handles is advisable. Titanium tongs may also be used but
titanium contamination must be avoided.
5.10 Stainless steel mould tongs for transferring moulds (5.4) in and out of the furnace (5.3) and, where
applicable, fusion equipment (5.7) of a length and construction suitable for safely performing this task.
They are typically of a two pronged forked design, the prongs fit the mould’s underside, securely
supporting it. A heat shield fitted to the front of the tongs’ handle is advisable.
5.11 Monitor disc, described in 7.4.4.
6 Sampling and samples
Bulk samples shall be taken in accordance with AS 4538.1 and test samples prepared in accordance
with AS 4538.2 Weighed test portions are extracted from test samples and may be dried or analysed
as-received. As-received samples often contain up to 3 % moisture and proper drying requires a 300 °C
treatment. Procedures for this are contained in ISO 806.
It is possible to fuse and produce borate discs from as-received test samples. However alumina used
for aluminium production typically contains a few mass per cent of particles greater than 150 micron,
consequently better repeatability is often achieved by grinding in a vibratory mill (5.6). Grinding is
recommended if coarse impurities are present from the manufacturing process. Examples of these
contaminants are refractory fragments from the calcination process or quartz particles not removed
during refining.
7 Procedure
7.1 General
Calibration is performed using a two-point regression. Determine the zero concentration point from a
blank calibration disc of flux and high purity Al O , and the high concentration point from a synthetic
2 3
calibration disc (SCD) derived from flux and an intermediate calibration glass (ICG). Make a correction
for the loss of mass on fusion of the flux, by establishing a value for the loss on fusion of each batch of flux.
Test sample discs are produced using a specified flux-to-sample ratio of 2:1 and the masses given in
Table 3, Table 5, and Table 6 are calculated for this ratio. Other ratios have been found to be satisfactory
but require re-calculation of the masses in these tables (see Annex C). Higher ratios than the specified
2:1 substantially improve dissolution and ease of disc preparation but count rates for analytes will
decrease. Ratios up to 5:1 are successfully used on modern spectrometers.
Also, different mould sizes may be used. This only requires that fusion masses in Table 3, Table 5, and
Table 6 be adjusted proportionately to the mould’s volume.
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ISO 23201:2015(E)

7.2 Preparation of calibration specimens
7.2.1 Determination of loss of mass on fusion of flux and flux correction
Determine the loss on fusion as follows:
a) weigh a clean dry platinum crucible (5.1) to the nearest 0,1 mg (m );
1
b) add approximately 4 g of the flux (4.1), weighed to the nearest 0,1 mg (m ), to the crucible and place
2
in a furnace at 300 °C ± 10 °C. Slowly increase the temperature to 1 100 °C ± 25 °C over 1 h;
c) after holding at 1 100 °C ± 25 °C for 20 min, remove from the furnace, allow to cool in a desiccator
and then re-weigh to the nearest 0,1 mg (m );
3
d) calculate the loss on fusion using Formula (1):
mm+− m
12 3
Loss on fusion (LOF)= (1)
m
2
where
m is the mass of clean dry crucible, in grams;
1
m is the mass of flux before heating, in grams;
2
m is the mass of crucible plus flux after heating, in grams.
3
To determine the mass of flux to be taken in 7.2.2, 7.2.3, 7.2.4 and 7.3, use Formula (2):
Corrected mass=mass givenL/(1− OF) (2)
7.2.2 Preparation of intermediate calibration glass (ICG)
Prepare the reagents by heating and cooling as shown in Clause 4.
Select the masses of reagents used to prepare the ICG in accordance with Table 2.
If any elements in Table 2 are not required, they may be omitted from the ICG. In this case, increase the
mass of flux in Table 2 by the equivalent mass of that reagent after fusion. (See Annex C).
Where reagents are omitted, the addition of extra flux will change the masses of flux and Al O from
2 3
those shown in Table 3. Use the information given in Annex C to calculate the new masses required.
Prepare the ICG as follows:
a) add the weighed reagents (as per Table 2, weighed to within 0,1 mg) to the crucible (5.1) and mix
thoroughly, ensuring that no contamination or loss of material occurs. Cover the crucible with its
lid and keep the crucible covered for the rest of the procedure, except while stirring the contents;
b) transfer the covered crucible and contents to the electric furnace (5.7), maintained at 300 °C ± 10 °C;
c) slowly increase the furnace temperature to 1 100 °C ± 25 °C over a period of not less than 1 h, at the
same heating rate as used in 7.2.1(b);
d) maintain this temperature for 5 min and then swirl the crucible and contents to mix the molten mass;
e) after a further 15 min at 1 100 °C ± 25 °C, remove the crucible and allow it to cool on a heat sink
(described in 5.7). When cool, the glass may be tapped from the crucible;
f) grind the glass in a vibratory mill (5.6).
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ISO 23201:2015(E)

Transfer the ground glass to an airtight container and store in the desiccator (5.2).
Table 2 — Reagent masses for intermediate calibration glass
Equivalent mass of reagent after
Mass
Conversion factor to
fusion
Reagent
mass of equivalent oxide
g
g
a
Flux 4,247 5 4,247 5
Na B O 5,191 3 0,308 2 1,600 0 Na2O
2 4 7
  3,591 3 B4O6 reports to flux
SiO 0,080 0 1,000 0 0,080 0
2
Fe O 0,080 0 1,000 0 0,080 0
2 3
CaCO 0,285 5 0,560 4 0,160 0
3
TiO 0,016 0 1,000 0 0,016 0
2
NH H PO 0,129 6 0,617 0 0,080 0
4 2 4
V O 0,016 0 1,000 0 0,016 0
2 5
ZnO 0,016 0 1,000 0 0,016 0
Mn O 0,017 2 0,930 1 0,016 0 MnO
3 4
  0,001 2 oxygen reports to flux
Ga O 0,032 0 1,000 0 0,032 0
2 3
K CO 0,023 5 0,681 2 0,016 0
2 3
CuO 0,016 0 1,000 0 0,016 0
Cr O 0,016 0 1,000 0 0,016 0
2 3
NiO 0,016 0 1,000 0 0,016 0
Total mass of ICG 10,000
a
This flux mass shall be loss corrected as per Formula (2).
7.2.3 Preparation of the synthetic calibration disk (SCD)
The masses of SCD reagents suitable for 35 mm and 40 mm moulds are given in Table 3. These masses
may be reduced or increased proportionally to suit any other size mould.
Table 3 — Reagent masses for synthetic calibration disc
Mass for 35 mm mould Mass for 40 mm mould
Reagent
g g
Intermediate calibration 0,125 0 0,187 5
glass
ab
Flux 3,902 0 5,853 0
b
High purity Al O 1,973 0 2,959 5
2 3
Total mass 6,00 9,00
a
This flux mass shall be loss corrected as per Formula (2).
b
If elements in Table 2 are omitted and/or a flux-to-sample ratio higher than 2:1 is used,
Annex C should be used to calculate new masses for Table 3.
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ISO 23201:2015(E)

Prepare the SCD as follows:
a) add the weighed reagents (to the nearest 0,5 mg) reagents to the crucible (5.1) and mix thoroughly,
ensuring that no contamination or loss of material occurs. To facilitate dissolution, intimate mixing
is essential;
b) transfer the crucible and contents to the furnace (5.7), which is maintained at 1 100 °C ± 25 °C;
c) maintain this temperature for 5 min, and then swirl the crucible to assist dissolution;
d) after a further 15 min at 1 100 °C ± 25 °C, swirl the crucible once more. Repeat the swirling at
5 min intervals until all alumina is fully dissolved. Place the mould (5.4) next
...