ISO 4688-1:2006
(Main)Iron ores — Determination of aluminium — Part 1: Flame atomic absorption spectrometric method
Iron ores — Determination of aluminium — Part 1: Flame atomic absorption spectrometric method
ISO 4688-1:2006 specifies a flame atomic absorption spectrometric method for the determination of the mass fraction of aluminium in iron ores. This method is applicable to mass fractions of aluminium between 0,1 % and 5,0 % in natural iron ores, iron ore concentrates and agglomerates, including sinter products.
Minerais de fer — Dosage de l'aluminium — Partie 1: Méthode par spectrométrie d'absorption atomique dans la flamme
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 4688-1
Second edition
2006-03-15
Iron ores — Determination of
aluminium —
Part 1:
Flame atomic absorption spectrometric
method
Minerais de fer — Dosage de l'aluminium —
Partie 1: Méthode par spectrométrie d'absorption atomique dans la
flamme
Reference number
ISO 4688-1:2006(E)
©
ISO 2006
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ISO 4688-1:2006(E)
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ISO 4688-1:2006(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 . 3
7.1 Number of determinations . 3
7.2 Test portion . 4
7.3 Blank test and check test. 4
7.4 Determination. 4
8 Expression of results . 6
8.1 Calculation of mass fraction of aluminium . 6
8.2 General treatment of results. 6
8.3 Oxide factor . 8
9 Test report . 8
Annex A (normative) Flowsheet of the procedure for the acceptance of analytical values for test
samples. 9
Annex B (informative) Derivation of repeatability and permissible tolerance equations . 10
Annex C (informative) Precision data obtained by international analytical trials . 11
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ISO 4688-1:2006(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 4688-1 was prepared by Technical Committee ISO/TC 102, Iron ore and direct reduced iron,
Subcommittee SC 2, Chemical analysis.
This second edition cancels and replaces the first edition (ISO 4688-1:1992), which has been technically
revised. It has been updated to alter the manner in which precision data are presented.
ISO 4688 consists of the following parts, under the general title Iron ores — Determination of aluminium :
⎯ Part 1: Flame atomic absorption spectrometric method
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INTERNATIONAL STANDARD ISO 4688-1:2006(E)
Iron ores — Determination of aluminium —
Part 1:
Flame atomic absorption spectrometric method
WARNING — This part of ISO 4688 may involve hazardous materials, operations and equipment. This
part of ISO 4688 does not purport to address all of the safety problems associated with its use. It is
the responsibility of the user of this part of ISO 4688 to establish appropriate health and safety
practices and determine the applicability of regulatory limitations prior to use.
1 Scope
This part of ISO 4688 specifies a flame atomic absorption spectrometric method for the determination of the
mass fraction of aluminium in iron ores.
This method is applicable to mass fractions of aluminium between 0,1 % and 5,0 % 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 7764, Iron ores — Preparation of predried test samples for chemical analysis
3 Principle
The test portion is decomposed by treatment with hydrochloric acid and a small amount of nitric acid.
The mixture is evaporated to dehydrate silica, followed by dilution and filtration.
The residue is ignited and silica is removed by evaporation with hydrofluoric and sulfuric acids. The residue is
then fused with sodium carbonate and the cooled melt is dissolved in the filtrate.
The solution obtained is aspirated into the flame of an atomic absorption spectrometer using a dinitrogen
oxide/acetylene burner.
The absorbance values obtained for aluminium are compared with those obtained from the calibration
solutions.
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ISO 4688-1:2006(E)
4 Reagents
During the analysis, use only reagents of recognized analytical grade and only distilled water or water of
equivalent purity.
4.1 Sodium carbonate (Na CO ), anhydrous.
2 3
4.2 Hydrochloric aid, ρ 1,19 g/ml.
4.3 Nitric acid, ρ 1,4 g/ml.
4.4 Hydrochloric acid, ρ 1,19 g/ml, diluted 1 + 9.
4.5 Hydrofluoric acid, ρ 1, 13 g/ml, 40 % (m/m), or ρ 1,185 g/ml, 48 % (m/m).
4.6 Sulfuric acid, ρ 1,84 g/ml, diluted 1 + 1.
4.7 Background solution
Dissolve 10 g of high purity iron [minimum purity 99,9 % (mass fraction)] of mass fraction of aluminium less
than 0,002 %, in 50 ml of hydrochloric acid (4.2) and oxidize by adding nitric acid (4.3) drop by drop.
Evaporate until a syrupy consistence is obtained. Add 20 ml of hydrochloric acid (4.2) and dilute to 200 ml with
water. Dissolve 17 g of sodium carbonate (4.1) in water and add it to the iron solution. Transfer the solution to
a 1 000 ml one-mark volumetric flask and dilute to volume with water.
4.8 Aluminium standard solution, 500 µg Al/ml.
Dissolve 0,5 000 g of high purity aluminium [minimum purity 99,9 % (mass fraction)] in 25 ml of hydrochloric
acid (4.2). Cool, transfer to a 1 000 ml one-mark volumetric flask, dilute to volume with water and mix.
4.9 Aluminium calibration solutions
Transfer 2,0 ml; 5,0 ml; 10,0 ml; 20,0 ml; 40,0 ml; and 50,0 ml portions of aluminium standard solution (4.8) to
200 ml volumetric flasks. Dilute to about 100 ml. Add 6 ml of hydrochloric acid (4.2) and 60 ml of background
solution (4.7) to each flask. Prepare a zero aluminium calibration solution by transferring 60 ml of the
background solution to a 200 ml volumetic flask, and add 6 ml of hydrochloric acid (4.2). Dilute all the
solutions to 200 ml with water and mix. (For an atomic absorption spectrometer having high sensitivity, smaller
portions of the standard solution may be used.)
5 Apparatus
Ordinary laboratory apparatus, including one-mark pipettes and one-mark volumetric flasks complying with the
specifications of ISO 648 and ISO 1042 respectively, and the following.
5.1 Platinum crucible, of capacity 30 ml.
5.2 Muffle furnace, capable of maintaining a temperature of approximately 1 100 °C.
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
flame is burning.
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ISO 4688-1:2006(E)
The atomic absorption spectrometer used in this method shall meet the following criteria.
a) Minimum sensitivity: the absorbance of the most concentrated aluminium calibration solution (4.9) shall
be 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) shall not be 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, shall be less than 1,5 % and 0,5 %, respectively, of the mean value of the absorbance of
the most concentrated calibration 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 may vary with each instrument. The following parameters were successfully used in
several laboratories and they can be used as guidelines. Solutions were aspirated into a dinitrogen oxide/acetylene flame
of a premix burner.
Aluminium hollow cathode lamp, mA. 25
Wavelength, nm . 396,2
Dinitrogen oxide flow rate, l/min . 13,8
Acetylene flow rate, l/min . 6,6
In systems where the values shown above for gas flow rates do not apply, the ratio of the gas flow rates may still be a
useful guideline.
6 Sampling and samples
6.1 Laboratory sample
For analysis, use a laboratory sample of minus 100 µm particle size 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.
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 °C ± 2 °C, as
specified in ISO 7764. (This is the predried test sample.)
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.
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