ISO 13312:2006
(Main)Iron ores — Determination of potassium —- Flame atomic absorption spectrometric method
Iron ores — Determination of potassium —- Flame atomic absorption spectrometric method
ISO 13312:2006 specifies a flame atomic absorption spectrometric method for the determination of the mass fraction of potassium in iron ores. This method is applicable to mass fractions of potassium between 0,002 5 % and 0,52 % in natural iron ores, iron ore concentrates and agglomerates, including sinter products.
Minerais de fer — Dosage du potassium — Méthode par spectrométrie d'absorption atomique dans la flamme
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 13312
Second edition
2006-06-01
Iron ores — Determination of
potassium — Flame atomic absorption
spectrometric method
Minerais de fer — Dosage du potassium — Méthode par spectrométrie
d'absorption atomique dans la flamme
Reference number
ISO 13312:2006(E)
©
ISO 2006
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ISO 13312:2006(E)
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ii © ISO 2006 – All rights reserved
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ISO 13312:2006(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Principle. 1
5 Reagents. 2
6 Apparatus . 2
7 Sampling and samples. 4
7.1 Laboratory sample. 4
7.2 Preparation of predried test samples . 4
8 Procedure . 4
8.1 Number of determinations . 4
8.2 Test portion . 4
8.3 Blank test and check test. 4
8.4 Determination. 5
8.4.1 Decomposition of the test portion . 5
8.4.2 Treatment of the solution. 5
8.4.3 Preparation of the set of calibration solutions . 5
8.4.4 Adjustment of atomic absorption spectrometer . 6
8.4.5 Atomic absorption measurements. 6
9 Expression of results . 6
9.1 Calculation of mass fraction of potassium . 6
9.2 General treatment of results. 7
9.2.1 Repeatability and permissible tolerance. 7
9.2.2 Determination of analytical result. 7
9.2.3 Between-laboratories precision . 7
9.2.4 Check for trueness . 8
9.2.5 Calculation of final result. 8
9.3 Oxide factor . 9
10 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
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ISO 13312:2006(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 13312 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 13312:1997), which has been technically
revised. It has been updated to alter the manner in which precision data are presented.
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INTERNATIONAL STANDARD ISO 13312:2006(E)
Iron ores — Determination of potassium — 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 mass fraction of potassium in iron ores.
This method is applicable to mass fractions of potassium between 0,002 5 % and 0,52 % 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
ISO 11323, Iron ore and direct reduced iron — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11323 apply.
4 Principle
The test portion is decomposed by treatment with hydrochloric acid and hydrofluoric acid, followed by
evaporation to dryness. The residue is wetted and the evaporation is repeated with a new portion of
hydrochloric acid. The residue is dissolved with hydrochloric acid followed by appropriate dilution. The solution
is aspirated into the air/acetylene flame of the atomic absorption apparatus.
The absorbance value obtained for potassium is measured in comparison with those obtained from calibration
solutions.
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ISO 13312:2006(E)
5 Reagents
During the analysis, use only reagents of recognized analytical grade, and only water that complies with
grade 2 of ISO 3696.
Reagents are to be selected or purified for the lowest possible blank value.
5.1 Hydrochloric acid, ρ 1,16 g/ml to 1,19 g/ml.
5.2 Hydrofluoric acid, ρ 1,13 g/ml, 40 % (m/m), or ρ 1,19 g/ml, 48 % (m/m).
5.3 Hydrochloric acid, ρ 1,16 g/ml to 1,19 g/ml, diluted 1 + 2.
5.4 Background solution
1)
Dissolve 43 g of high-purity iron oxide powder in 500 ml of hydrochloric acid (5.1). Allow to cool and dilute
with water to 1 000 ml.
5.5 Potassium, standard solution, 20 µg K/ml.
Pulverize about 3 g of high-purity potassium chloride in an agate mortar, dry in an oven at 105 °C to 110 °C
for 2 h, and allow to cool to room temperature in a desiccator. Dissolve 1,907 g in water, dilute with water to
1 000 ml in a volumetric flask and mix.
2)
Transfer 10,0 ml of this solution to a 500 ml volumetric flask, dilute with water to volume and mix.
Store this standard solution in a plastic bottle.
1 ml of this standard solution contains 20 µg of potassium.
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 Polytetrafluoroethylene (PTFE) beakers, of capacity 100 ml, provided with PTFE covers.
6.2 PTFE-coated magnetic stirring bars.
6.3 PTFE digestion bomb.
6.4 Plastic pipettes.
6.5 Plastic volumetric flasks and storage bottles.
6.6 Magnetic stirring hotplates.
NOTE Platinum vessels may be used instead of PTFE beakers.
Except where stated, glass equipment should be avoided, as it could contaminate the solutions.
1) Instead of iron oxide, the use of metallic iron with a suitable oxidant is permitted. (The alkali content of the oxidant
shall be low.)
2) Glass equipment may be used.
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ISO 13312:2006(E)
To obtain reliable values, the equipment should be cleaned and checked as follows.
a) Rinse all volumetric ware, including the pipettes used for preparing the calibration solutions, with dilute
hydrochloric acid (5.3) before use. Check the calibration regularly or as needed.
b) Clean PTFE vessels and stirring bars by stirring with 50 ml of dilute hydrochloric acid (5.3) and by heating
for 15 min. Discard the rinsings and conduct a blank test in each vessel in turn, exactly as specified in 8.3.
If any absorbance value is above the limit specified in 8.3, the cleaning procedure should be repeated or
acid reagents of a higher purity should be used. At no stage should the stirring bars be handled with the
fingers.
c) Platinum vessels, exclusively used for potassium analysis according to this International Standard, can be
cleaned by the same method as the PTFE vessels [see b)]. Otherwise, they should be pre-cleaned by
fusion with lithium tetraborate or lithium borate, until the absorbance readings fall to those for the lithium
salt alone.
d) Rinse storage bottles with dilute hydrochloric acid (5.3) before use.
6.7 Atomic absorption spectrometer.
WARNING — Follow the manufacturer's instructions for igniting and extinguishing the air/acetylene
flame to avoid possible explosion hazards. Wear tinted safety glasses whenever the burner is in
operation.
The atomic absorption spectrometer shall meet the following criteria.
a) Minimum sensitivity: the absorbance of the most concentrated calibration solution (see 8.4.3) shall be at
least 0,25.
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 will vary with each instrument. The following parameters were successfully used in
several laboratories and they can be used as guidelines. Solutions were aspirated into an air/acetylene flame of a premix
burner.
⎯ hollow cathode lamp, mA 10
⎯ wavelength, nm 766,5
⎯ air flow-rate, l/min 10
⎯ acetylene flow-rate, l/min 2
In systems where the values shown for gas flow-rates do not apply, the ratio of the gas flow-rates may still be a useful
guideline.
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ISO 13312:2006(E)
7 Sampling and samples
7.1 Laboratory sample
For analysis, use a laboratory sample of minus 100 µm particle size
...
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