ISO 15634:2005
(Main)Iron ores — Determination of chromium content — Flame atomic absorption spectrometric method
Iron ores — Determination of chromium content — Flame atomic absorption spectrometric method
ISO 15634:2005 specifies a flame atomic absorption spectrometric method for the determination of the chromium content of iron ores. ISO 15634:2005 is applicable to chromium contents between 0,001 6 % and 0,1 % (mass fractions) in natural iron ores, iron ore concentrates and agglomerates, including sinter products.
Minerais de fer — Dosage du chrome — Méthode par spectrométrie d'absorption atomique dans la flamme
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 15634
First edition
2005-05-15
Iron ores — Determination of chromium
content — Flame atomic absorption
spectrometric method
Minerais de fer — Dosage du chrome — Méthode par spectrométrie
d'absorption atomique dans la flamme
Reference number
ISO 15634:2005(E)
©
ISO 2005
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ISO 15634:2005(E)
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ii © ISO 2005 – All rights reserved
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ISO 15634:2005(E)
Contents Page
Foreword. iv
1 Scope. 1
2 Normative references . 1
3 Principle . 1
4 Reagents . 2
5 Apparatus. 2
6 Sampling and samples . 3
6.1 Laboratory sample. 3
6.2 Preparation of predried test samples . 3
7 Procedure. 4
7.1 Number of determinations . 4
7.2 Test portion . 4
7.3 Blank test and check test. 4
7.4 Determination . 4
7.4.1 Decomposition of the test portion . 4
7.4.2 Removal of iron . 5
7.4.3 Treatment of the residue . 5
7.4.4 Preparation of the calibration solutions. 5
7.4.5 Preparation of the flame setting solution. 6
7.4.6 Adjustment of the atomic absorption spectrometer . 6
7.4.7 Atomic absorption measurements. 6
8 Expression of results. 6
8.1 Calculation of chromium content. 6
8.2 General treatment of results . 7
8.2.1 Repeatability and permissible tolerance . 7
8.2.2 Determination of analytical result . 7
8.2.3 Between-laboratories precision . 7
8.2.4 Check for trueness. 8
8.2.5 Calculation of final result . 8
8.3 Oxide factor for conversion to chromium oxide. 9
9 Test report. 9
Annex A (normative) Flowsheet of the procedure for the acceptance of analytical values for test
samples. 10
Annex B (informative) Derivation of repeatability and permissible tolerance equations . 11
Annex C (informative) Precision data obtained by international analytical trials. 12
Bibliography . 13
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ISO 15634:2005(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 15634 was prepared by Technical Committee ISO/TC 102, Iron ore and direct reduced iron,
Subcommittee SC 2, Chemical analysis.
This first edition of ISO 15634, together with ISO 15633, cancels and replaces ISO 9685:1991, which has
been technically revised.
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INTERNATIONAL STANDARD ISO 15634:2005(E)
Iron ores — Determination of chromium content — Flame
atomic absorption spectrometric method
WARNING — This International Standard may involve hazardous materials, operations and equipment.
This International Standard does not purport to address all of the safety problems associated with its
use. It is the responsibility of the user of this International Standard to establish appropriate health
and safety practices and determine the applicability of regulatory limitations prior to use.
1 Scope
This International Standard specifies a flame atomic absorption spectrometric method for the determination of
the chromium content of iron ores.
This method is applicable to chromium contents between 0,001 6 % and 0,1 % (mass fractions) in natural iron
ores, iron ore concentrates and agglomerates, including sinter products.
2 Normative references
The following referenced documents are indispensable for the application 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 — One-mark pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
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
3 Principle
The test portion is decomposed by treatment with hydrochloric and nitric acids.
The major portion of iron in the filtrate is removed by extraction with 4-methylpentan-2-one.
The insoluble residue is ignited and the silicon dioxide is removed by evaporation with hydrofluoric and sulfuric
acids. The residue is fused with a mixture of sodium carbonate and sodium tetraborate, and then dissolved with
hydrochloric acid and combined with the main solution.
The solution is aspirated into the flame of an atomic absorption spectrometer using a nitrous oxide-acetylene
burner.
The absorbance values obtained are compared with those obtained from the calibration solutions.
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ISO 15634:2005(E)
4 Reagents
During the analysis, use only reagents of recognized analytical grade.
4.1 Water, complying with grade 2 as defined in ISO 3696.
4.2 Sodium carbonate, (Na CO ), anhydrous powder.
2 3
4.3 Sodium tetraborate, (Na B O ), anhydrous powder.
2 4 7
4.4 Lithium tetraborate, (Li B O ), anhydrous powder.
2 4 7
4.5 Hydrochloric acid, ρ 1,16 g/ml to 1,19 g/ml.
4.6 Hydrochloric acid, ρ 1,16 g/ml to 1,19 g/ml, diluted 2 + 1.
4.7 Hydrochloric acid, ρ 1,16 g/ml to 1,19 g/ml, diluted 1 + 1.
4.8 Hydrochloric acid, ρ 1,16 g/ml to 1,19 g/ml, diluted 2 + 100.
4.9 Nitric acid, ρ 1,4 g/ml.
4.10 Nitric acid, ρ 1,4 g/ml, diluted 1 + 1.
4.11 Hydrofluoric acid, ρ 1,13 g/ml, 40 % (mass fraction), or ρ 1,19 g/ml, 48 % (mass fraction).
4.12 Sulfuric acid, ρ 1,84 g/ml.
4.13 Sulfuric acid, ρ 1,84 g/ml, diluted 1 + 1.
4.14 Methylpentan-2-one, (methyl isobutyl ketone, MIBK).
4.15 Chromium standard solution A, 100 µg Cr/ml.
Dissolve 0,100 0 g of chromium metal [purity > 99,9 % (mass fraction), (see Note to 4.16)] in 20 ml of
hydrochloric acid (4.7). After cooling, transfer to a 1 000 ml one-mark volumetric flask quantitatively, dilute to
volume with water (4.1) and mix.
4.16 Chromium standard solution B, 10 µg Cr/ml.
Transfer 100,0 ml of chromium standard solution A (4.15) to a 1 000 ml one-mark volumetric flask. Dilute to
volume with water and mix.
NOTE The purity of the metals stated on the certificates does not generally take into account the presence of
adsorbed gases like oxygen, carbon monoxide, etc.
5 Apparatus
Ordinary laboratory apparatus, including one-mark pipettes and one-mark volumetric flasks complying with the
specifications of ISO 648 and ISO 1042, and the following.
5.1 Platinum crucible, of minimum capacity 25 ml.
5.2 Muffle furnace.
5.3 Atomic absorption spectrometer, equipped with a dinitrogen oxide-acetylene burner.
WARNING — Follow the manufacturer's instructions for igniting and extinguishing the dinitrogen
oxide-acetylene flame to avoid possible explosion hazards. Wear tinted safety glasses whenever the
burner is in operation.
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ISO 15634:2005(E)
The atomic absorption spectrometer used in this method shall meet the following criteria:
a) Minimum sensitivity — the absorbance of the most concentrated calibration solution (see 7.4.4) is at
least 0,3;
b) Graph linearity — the slope of the calibration graph covering the top 20 % of the concentration range
(expressed as a change in absorbance) is not less than 0,7 of the value of the slope for the bottom 20 %
of the concentration range determined in the same way;
c) Minimum stability — the standard deviation of the absorbance of the most concentrated calibration
solution and that of the zero calibration solution, each being calculated from a sufficient number of
repetitive measurements, are less than 1,5 % and 0,5 % respectively of the mean value of the
absorbance of the most concentrated solution.
The use of a strip-chart recorder and/or digital readout device is recommended to evaluate criteria a), b) and
c) and for all subsequent measurements.
NOTE Instrument parameters will vary with each instrument. The following parameters were successfully used in
several laboratories and they can be used as guidelines:
hollow-cathode lamp 10 mA;
wavelength 357,9 nm:
dinitrogen oxide flow rate ≈10 l/min.;
acetylene flow rate 5 l/min.
A dinitrogen oxide-acetylene flame was used.
In systems where the values shown above for gas flow rates do not apply, the ratio of the gas flow rates can still
be a useful guideline.
6 Sampling and samples
6.1 Laboratory sample
For analysis, use a laboratory sample of particle size of less than 100 µm which has been taken and prepared
in accordance with ISO 3082. In the case of ores containing significant contents of combined water or
oxidizable compounds, use a particle size of less than 160 µm.
NOTE A guideline on significant contents of combined water and oxidizable compounds is incorporated in ISO 7764.
Ensure that the sample has not been pulverized in a nickel/chromium pot.
6.2 Preparation of predried test samples
Thoroughly mix the laboratory sample and, taking multiple increments, extract a test sample in such a way
that it is representative of the whole contents of the container. Dry the test sample at (105 ± 2)°C as specified
in ISO 7764. (This is the predried test sample.)
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ISO 15634:2005(E)
7 Procedure
7.1 Number of determinations
Carry out the analysis at least in duplicate in accordance with Annex A, 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 this particular analytical method, this condition implies that the repetition of the procedure be carried
out either by the same operator at a different time or by a different operator including, in either case, appropriate
recalibration.
7.2 Test portion
Taking several increments, weigh, to the nearest 0,000 2 g, approximately 1 g of the predried test sample
obtained in accordance with 6.2.
The test portion should be taken and weighed quickly, in order to avoid reabsorption of moisture.
7.3 Blank test and check test
In each run, one blank test and one an
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