ISO 22682:2017

Iron ores — Determination of trace elements — Plasma spectrometric method

ISO 22682:2017 specifies a method for the determination of phosphorus, vanadium, titanium, copper, nickel, chromium, barium and cobalt in iron ores, by inductively coupled plasma atomic emission spectrometry (ICP-AES).

Minerais de fer — Détermination d'éléments traces — Méthode par spectrométrie avec plasma

General Information

• Status: Published
• Publication Date: 14-Aug-2017
• ICS: 73.060.10 - Iron ores
• Technical Committee: ISO/TC 102/SC 2 - Chemical analysis
• Drafting Committee: ISO/TC 102/SC 2 - Chemical analysis
• Current Stage: 9060 - Close of review
• Start Date: 03-Mar-2028

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 22682
First edition
2017-08
Iron ores — Determination of trace
elements — Plasma spectrometric
method
Minerais de fer — Détermination d’éléments traces — Méthode par
spectrométrie avec plasma
Reference number
ISO 22682:2017(E)
©
ISO 2017

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ISO 22682:2017(E)

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© ISO 2017, Published in Switzerland
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ISO 22682:2017(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principle . 2
5 Reagents . 2
6 Apparatus . 4
7 Sampling and samples . 4
7.1 Laboratory sample . 4
7.2 Preparation of predried test samples . 5
8 Procedure. 5
8.1 Number of determinations . 5
8.2 Test portion . 5
8.3 Blank test and check test . 5
8.4 Determination . 5
8.4.1 Decomposition of the test portion . 5
8.4.2 Adjustment of spectrometer . 6
9 Calculation of results . 7
9.1 Calibration graph . 7
9.2 Correction of spectral interference . 8
9.3 Standardization of calibration graph (drift correction) . 9
9.4 General treatment of results .10
9.4.1 Repeatability and permissible tolerances .10
9.4.2 Determination of analytical result .10
9.4.3 Check for trueness .11
9.4.4 Calculation of final result .12
9.5 Oxide factors .12
10 Test report .12
Annex A (informative) Suggested calibration solutions .14
Annex B (normative) Plasma spectrometer performance tests .15
Annex C (normative) Flowchart of the procedure for the acceptance of analytical values of
test samples .18
Annex D (informative) Derivation of repeatability and permissible tolerance formulae .19
Annex E (informative) Precision data obtained by international analytical trials .20
Bibliography .25
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ISO 22682:2017(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).
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URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 102, Iron ore and direct reduced iron,
Subcommittee SC 2, Chemical analysis.
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INTERNATIONAL STANDARD ISO 22682:2017(E)
Iron ores — Determination of trace elements — Plasma
spectrometric method
CAUTION — This document may involve hazardous operations and equipment. This document
does not purport to address all of the safety issues 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 its use.
1 Scope
This document specifies a method for the determination of phosphorus, vanadium, titanium, copper,
nickel, chromium, barium and cobalt in iron ores, by inductively coupled plasma atomic emission
spectrometry (ICP-AES).
This method is applicable to the concentration ranges (mass fraction) given in Table 1, in natural iron
ores, iron ore concentrates and agglomerates, including sinter products.
Table 1 — Concentration ranges
Concentration range for Concentration range for
Element referee purpose non-referee purpose
% (mass fraction) % (mass fraction)
P 0,000 2 to 0,150 0,000 2 to 0,150
V 0,003 0 to 0,024 0,003 0 to 0,024
Ti 0,015 0 to 0,120 0,015 0 to 0,120
Cu 0,0014 to 0,250 0,001 4 to 0,250
Ni 0,005 0 to 0,090 0,005 0 to 0,090
Cr 0,004 0 to 0,015
Ba 0,002 8 to 0,035
Co 0,002 0 to 0,100
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 648, Laboratory glassware — Single-volume pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 2596, Iron ores — Determination of hygroscopic moisture in analytical samples — Gravimetric, Karl
Fischer and mass-loss methods
ISO 3082, Iron ores — sampling and sample preparation procedures
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 7764, Iron ores — Preparation of predried test samples for chemical analysis
ISO 11323, Iron ore and direct reduced iron — Vocabulary
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3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11323 apply.
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 https:// www .iso .org/ obp
4 Principle
The test portion is decomposed with L-ascorbic acid, hydrofluoric acid, concentrated hydrochloric acid,
concentrated nitric acid and then evaporated to dryness. The dry mass is dissolved in hydrochloric acid
(1 + 1) and the solution is made up to 100 ml.
The solution is diluted to volume and measured on an ICP spectrometer. Final results are read from a
calibration graph prepared using standard calibration solutions.
5 Reagents
During the analysis, use only highly pure reagents of recognized analytical grade and only water that
complies with grade 2 of ISO 3696.
5.1 High-purity iron, metal, of minimum purity grade 99,99 % (mass fraction).
5.2 Hydrochloric acid, ρ 1,16 g/ml to 1,19 g/ml, diluted 1 + 1.
5.3 Nitric acid, ρ 1,38 g/ml to 1,4 g/ml
5.4 Hydrofluoric acid, ρ 1,13 g/ml to ρ 1,16 g/ml.
5.5 Sulfuric acid, p.a. grade.
5.6 L-ascorbic acid, C H O .
6 8 6
5.7 Stock solutions.
Stock solutions shall be prepared by convenient handling moisture-free high-purity salts, dried until a
constant mass and cooled in a desiccator. High-purity metals of minimum purity grade of 99,9 % (mass
fraction) can also be used to prepare vanadium, titanium, copper, nickel and chromium stock solutions.
Stock solutions may also be prepared by independent laboratories or reagent suppliers.
5.7.1 Phosphorus, 1 000 μg/ml.
Dissolve 4,393 6 g of potassium dihydrogen orthophosphate (KH PO ) in about 200 ml of water in a
2 4
1 000 ml one-mark volumetric flask. When the dissolution is complete, dilute to volume with water
and mix.
5.7.2 Vanadium, 1 000 μg/ml.
Dissolve 1,000 0 g of high-purity vanadium metal or 2,296 3 g of ammonium metavanadate (NH VO ) in
4 3
20 ml of nitric acid (5.3) in a covered tall-form beaker with heating. When dissolution is complete, cool
and transfer to a 1 000 ml one mark-volumetric flask, dilute to volume with water and mix.
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5.7.3 Titanium, 1 000 μg/ml.
Dissolve 1,000 0 g of high-purity titanium metal in 100 ml of hydrochloric acid (5.2) in a covered tall-
form beaker with heating or 4,135 1 g of high-purity ammonium hexafluorotitanate [(NH ) TiF ] in
4 2 6
warm distilled water containing drops of hydrofluoridic acid (5.4) in a covered tall-form PTFE beaker.
When dissolution is complete, cool and transfer to a 1 000 ml one-mark volumetric flask, dilute to
volume with water and mix.
5.7.4 Copper, 1 000 μg/ml.
Dissolve 1,000 0 g of high-purity copper metal in 20 ml of nitric acid (5.3) in a covered tall-form beaker.
When dissolution is complete, add about 20 ml of water and heat to liberate oxides of nitrogen. Cool and
transfer to a 1 000 ml one-mark volumetric flask, dilute to volume with water and mix.
5.7.5 Nickel, 1 000 μg/ml.
Dissolve 1,000 0 g of high-purity nickel metal in 20 ml of nitric acid (5.3) in a covered tall-form beaker
with heating. When dissolution is complete, cool and transfer to a 1 000 ml one-mark volumetric flask,
dilute to volume with water and mix.
5.7.6 Chromium, 1 000 μg/ml.
Dissolve 1,000 0 g of high-purity chromium metal in 100 ml of nitric acid (5.3) or 7,695 8 g of
chromium (III) nitrate nonahydrate [Cr(NO ) ·9H O] in 20 ml of nitric acid (5.3) in a covered tall-form
3 3 2
beaker with heating. When dissolution is complete, cool and transfer to a 1 000 ml one-mark volumetric
flask, dilute to volume with water and mix.
5.7.7 Barium, 1 000 μg/ml.
Dissolve 1,437 0 g of high-purity barium carbonate (BaCO ) in 20 ml of nitric acid (5.3) in a covered
3
tall-form beaker with heating. When dissolution is complete, cool and transfer to a 1 000 ml one-mark
volumetric flask, dilute to volume with water and mix.
5.7.8 Cobalt, 1 000 μg/ml.
Dissolve 2,018 2 g of cobalt carbonate (CoCO ) in 20 ml of nitric acid (5.3) in a covered tall-form beaker
3
with heating. When dissolution is complete, cool and transfer to a 1 000 ml one-mark volumetric flask,
dilute to volume water and mix.
5.8 Calibration and reference solutions.
Calibration solutions are defined as the solutions required for the determination of the line peak
and background position(s) and for plotting the calibration graphs of the elements analysed. Their
concentration ranges in solution, expressed in micrograms per millilitre, are determined with reference
to the performance parameter values and the linearity response of the instrument. A minimum of five
calibration solutions is necessary to cover the concentration ranges given in Table 1. For test samples
having narrower concentration ranges, calibration solutions are prepared to cover the region of
interest.
In the case of nonlinearity, either a less sensitive line shall be used or appropriate dilutions of sample
and calibration solutions shall be carried out.
NOTE For the suggested lines shown in Table 2, the calibration solutions prepared as recommended in
Annex A will be in agreement with the performance test figures.
To comply with the requirements of similarity between the test sample and the calibration solutions, iron
and acids shall be added (see Note in Table A.1). For each calibration solution, the procedure described in
8.4.1 shall be followed, replacing the test sample with a suitable amount of high-purity iron (5.1).
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In addition, to comply with the requirements of similarity, calibration solutions and test samples shall
be prepared from reagents taken from the same containers, to minimize purity differences between
batches.
6 Apparatus
Ordinary laboratory equipment, including one-mark pipettes and one-mark volumetric flasks complying
with the specifications of ISO 648 and ISO 1042 respectively, and the following.
6.1 Analytical balance, capable of weighing to the nearest 0,000 1 g.
6.2 Platinum or suitable platinum alloy crucibles, having a minimum volume of 30 ml.
6.3 Muffle furnace, to provide a minimum temperature of 1 020 °C.
6.4 ICP spectrometer.
Any conventional ICP spectrometer, with radial or axial observation path may be used, provided that
the instrument has been initially set up according to the manufacturer’s recommendations and that it
complies with the performance test (see 8.4.2.2), carried out prior to the measurements.
Suggested analytical lines are shown in Table 2. These lines are found to be relatively free of significant
interferences from the matrix elements, but they shall be carefully checked for spectral interference,
background and ionization, with appropriate corrections carried out prior to their adoption. Failure to
attain the recommended performance parameters may indicate interference.
For the analysis of samples having concentrations in the background equivalent concentration (C )
BE
region or lower, as defined in Table 3, careful assessment of the need for background correction for the
particular line chosen is recommended prior to calibration and analysis.
Table 2 — Suggested analytical lines
Element Wavelength, nm
P 178,290
V 311,071/309,311/310,230
Ti 334,941/336,120
Cu 327,396/224,700/324,75
Ni 231,604
Cr 267,716
Ba 455,405
Co 228,616/238,892
7 Sampling and samples
7.1 Laboratory sample
For analysis, use a laboratory sample of minus 100 μm which has been taken and prepared in accordance
with ISO 3082. In the case of ores having significant contents of combined water or oxidizable
compounds, use a particle size of minus 160 μm.
NOTE A guideline on significant contents of combined water and oxidizable compounds is incorporated in
ISO 7764.
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7.2 Preparation of predried test samples
Thoroughly mix the laboratory sample and, taking multiple increments, extract a test sample in
such a manner that it is representative of the whole contents of the container. Dry the test sample at
105 °C ± 2 °C as specified in ISO 7764. (This is the predried test sample.)
For ores having significant content of combined water or oxidizable compounds, an air-equilibrated
test sample shall be prepared in accordance with ISO 2596 to determine the dry sample mass using the
hygroscopic moisture.
8 Procedure
8.1 Number of determinations
Carry out the analysis at least in duplicate in accordance with Annex C, independently, on one predried
test sample.
NOTE The expression “independently” means that the second and any subsequent result is not affected
by the previous result(s). For the particular analytical method, this condition implies that the repetition of the
procedure is carried out either by the same operator at a different time, or by a different operator, including
appropriate recalibration in either case.
8.2 Test portion
Taking several increments, weigh, to the nearest 0,000 1 g, approximately 1,0 g of the predried test
sample obtained in accordance with 7.2.
The test portion should be taken and weighed quickly to avoid re-adsorption of moisture.
8.3 Blank test and check test
In each run, one blank test and one analysis of a certified reference material of the same type of ore shall
be carried out in parallel with the analysis of the ore sample(s) under the same conditions. A predried
test sample of the certified reference material shall be prepared as specified in 7.2.
For the blank test, a suitable amount of high-purity iron (5.1) shall be used in place of the test sample.
The certified reference material shall be of the same type as the sample to be analysed and the
properties of the two materials shall be sufficiently similar to ensure that in either case no significant
changes in the analytical procedure become necessary. Where a certified reference material is not
available, a reference material may be used (see 9.4.4).
Where the analysis is carried out on several samples at the same time, the blank value may be
represented by one test, provided that the procedure is the same and the reagents used are from the
same reagent bottles.
Where the analysis is carried out on several samples of the same type of ore at the same time, the
analytical value of one certified reference material may be used.
8.4 Determination
8.4.1 Decomposition of the test portion
Transfer the weighed test portion to a 250 ml capacity PTFE Erlenmeyer flask with cover.
Add 0,5 g of L-ascorbic acid (5.6), moisten with water, 5,0 ml of hydrofluoric acid (5.4) and 30 ml of
concentrated hydrochloric acid (5.2) and take to a hotplate for 2 h. (The hotplate temperature shall be
controlled between 120 °C and 140 °C; if necessary use a thermometer inserted in a beaker containing
sulfuric acid.)
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Add, after complete dissolution, concentrated nitric acid (5.3) drop by drop until complete oxidation of
the sample (approximately 10 ml) and keep heating in the hotplate for 30 min with the cover, and after
that time, remove the cover and take to complete dryness.
Recover in 20 ml of hydrochloric acid 1 + 1 (5.2), and take to the hotplate until the dissolution is
completed. Filter in white class filter paper.
Transfer the filtrate to a 100 ml volumetric flask. Make up to volume. If necessary, confirm the absence
of undecomposed material by transferring the filter to a pre-weighed platinum crucible followed by
gentle burn in a Bunsen burner, followed by ashing at 900 °C in a muffle furnace. Confirm absence of
residue by taking the difference of crucible masses, before and after the ashing operation.
Carry out also a blank test using all reagents.
8.4.2 Adjustment of spectrometer
8.4.2.1 General
The ICP spectrometer shall be initially adjusted according to the manufacturer’s recommendations and
laboratory practice for quantitative analysis.
The definition of specific ICP components such as type of plasma observation view, torch, nebulizer
as well as all instrumental parameters such as plasma power, test sample solution uptake rate, etc.,
shall be defined during the performance test optimization procedure (see 8.4.2.2), to comply with the
performance parameter figures specified in Table 3, and shall remain unchanged thereafter during
calibration and analysis.
8.4.2.2 Performance test
The performance test is devised with the purpose of optimizing the ICP spectrometer to carry out
the analysis with adequate sensitivity and precision. Target values for these figures, called method
performance parameters are listed in Table 3.
The test is based on the determination of the following three parameters:
— detection limit (L );
D
— background equivalent concentration (C );
BE
— short-term precision (σ ).
r,Nmin
The definitions of these terms and the procedure for their evaluation shall be as described in Annex B.
The procedure shall be carried out as many times as necessary, with the optimization of the instrument
parameters after each turn, until the figures obtained are equal or lower than those given in Table 3.
Table 3 — Recommended performance parameters
λ Adopted C Adopted L σ
BE D r,Nmin
Element
nm μg/ml μg/ml %
P 178,287 0,86 0,025 2
V 310,230 0,44 0,021 2
Ti 334,941 0,12 0,003 2
Cu 324,75 0,28 0,003 2
Ni 231,604 0,53 0,016 2
Cr 267,716 0,25 0,007 2
Ba 455,403 0,06 0,002 2
Co 228,616 0,30 0,020 5
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8.4.2.3 Measurements
8.4.2.3.1 Calibration solutions
Prepare a series of at least five calibration solutions plus a blank, all containing the equivalent of
6 000 µg/ml of iron (Fe), from 0,6 g of high-purity iron (5.1) portions, following exactly the decomposition
of the test portion procedure described in 8.4.1. Add convenient amounts of each single element stock
solutions (5.7.1 to 5.7.8) to cover the required analytical range. A suggested set of calibration solutions
is given in Annex A.
Aspirate the calibration solutions in order of increasing concentration, starting with the blank (zero)
calibration solution.
Aspirate water between each solution and repeat the measurements at least twice. Take the average of
the readings.
If saturation of detector(s) occurs while running the most concentrated calibration solutions, establish
the limit of linearity range of the curve and either choose a less sensitive line from this limit or
conveniently dilute these calibration standards, plotting a new specific calibration curve to cover this
high range of concentration, adding, if necessary, new calibration solutions, to comply with a required
minimum of five points per curve.
For the concentration ranges covered by this procedure, it is necessary to verify if the chosen lines
need background correction. This correction is performed by means of careful choice of their
background position(s) prior to calibration and analysis. To assess the background position(s) all the
5 calibration solutions, the NFe solution (to be used for assessment of interferences and contamination
of reagents) and a typical test sample, submitted to dissolution according to 8.4.1, should be scanned
around the chosen lines. Except for the NFe calibration solution, scanned to test for eventual reagents
contamination, all others should present background levels not significantly different from the test
solution, indicating that matrix matching, in terms of viscosity and surface tension has been achieved.
After initial calibration has been established, a two-point recalibration procedure can be used for
routine analysis. In this case, proceed according to 9.3.
8.4.2.3.2 Test solutions
Immediately after aspiration of the calibration solutions, commence running the first test solution,
followed by the certified reference material (CRM). Continue aspirating test solutions and CRMs
alternately. Aspirate water between each measurement.
This procedure should preferably be repeated at least twice.
9 Calculation of results
9.1 Calibration graph
Prepare a calibration graph by plotting the intensity values obtained from the calibration solution
against its equivalent element concentration.
Read the intensity values for the test solution and obtain their respective concentration values from
calibration graphs.
If spectral interferences are found to exist, corrections shall be carried out in accordance with 9.2.
Calibration graphs are preferably obtained using statistical procedures (e.g. least squares). Computer-
assisted spectrometers usually incorporate such a facility.
Correlation coefficients and root mean square (RMS) values obtained shall be within the laboratory
acceptance criteria.
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Calibration-graph drift-correction procedures may be used, provided that they are carried out in
accordance with 9.3 immediately before analysis of the test solutions.
9.2 Correction of spectral interference
A correction method for spectral interferences by using synthetic standard solution is recommended. A
suggested procedure is described below.
Plot a calibration graph by using binary (iron plus reagents and an analyte) synthetic solution series for
the analyte interfered element (named “i”). Suggested calibration solutions (see Annex A) may be used
as long as
...