ISO 13899-2:2005

INTERNATIONAL ISO
STANDARD 13899-2
First edition
2005-06-15


Steel — Determination of Mo, Nb and W
contents in alloyed steel — Inductively
coupled plasma atomic emission
spectrometric method —
Part 2:
Determination of Nb content
Aciers — Dosage du Mo, du Nb et du W dans les aciers alliés —
Méthode par spectrométrie d'émission atomique avec plasma induit par
haute fréquence —
Partie 2: Dosage du Nb





Reference number
ISO 13899-2:2005(E)
©
ISO 2005

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ISO 13899-2:2005(E)
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ISO 13899-2:2005(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Principle. 1
4 Reagents. 2
5 Apparatus . 3
6 Sampling and samples. 4
7 Procedure . 4
7.1 Preparation of test solution, T . 4
n
7.2 Preparation for spectrometric measurements. 5
7.3 Pre-analysis of the test solution . 5
7.4 Preparation of calibration solutions for bracketing, K and K . 6
Ln Hn
7.5 Analysis of test solutions . 6
8 Expression of results . 6
8.1 Method of calculation. 6
8.2 Precision. 6
9 Test report . 7
Annex A (normative) Procedure for the determination of instrumental criteria. 8
Annex B (informative) Suggested lines together with possible spectral interferences in the
determination of Nb in steel by ICP-AES. 10
Annex C (informative) Additional information on the international cooperative tests . 11
Annex D (informative) Graphical representation of precision data . 13

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ISO 13899-2:2005(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 13899-2 was prepared by Technical Committee ISO/TC 17, Steel, Subcommittee SC 1, Methods of
determination of chemical composition.
ISO 13899 consists of the following parts, under the general title Steel — Determination of Mo, Nb and W
contents in alloyed steel — Inductively coupled plasma atomic emission spectrometric method:
 Part 1: Detemination of Mo content
 Part 2: Detemination of Nb content
 Part 3: Detemination of W content

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INTERNATIONAL STANDARD ISO 13899-2:2005(E)

Steel — Determination of Mo, Nb and W contents in alloyed
steel — Inductively coupled plasma atomic emission
spectrometric method —
Part 2:
Determination of Nb content
1 Scope
This International Standard specifies a method for the determination of the niobium content in steel by means
of inductively coupled plasma emission spectrometry.
This method is applicable to niobium contents between 0,005 and 5 % (mass fraction).
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 648:1977, Laboratory glassware — One mark pipettes
ISO 1042:1983, Laboratory glassware — One mark volumetric flasks
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods
ISO 5725-1:1994, Accuracy (trueness and precision) of measurement methods and results — Part 1: General
principles and definitions
ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic
method for the determination of repeatability and reproducibility of a standard measurement method
ISO 5725-3:1994, Accuracy (trueness and precision) of measurement methods and results — Part 3:
Intermediate measures of the precision of a standard measurement method
ISO 14284:1996, Steel and iron — Sampling and preparation of samples for the determination of chemical
composition
3 Principle
The sample is dissolved in a hydrochloric, nitric and hydrofluoric acid mixture and fumed with a phosphoric
and perchloric acid mixture. Hydrofluoric acid and an internal standard element (if used) are added and the
solution is diluted to known volume. The solution is filtered and nebulized into an ICP and the intensity of the
emitted light from each element is measured simultaneously with the light emitted from the internal standard
element.
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ISO 13899-2:2005(E)
The method uses a calibration based on close matrix matching of the calibration solutions to the sample and
close bracketing of the niobium content around the approximate concentration of niobium in the sample to be
analysed. This compensates for matrix interferences and provides high accuracy, even in highly alloyed steels
where spectral interferences can be severe. Nonetheless, all interferences shall be kept to a minimum and it is
therefore essential that the spectrometer used meets the performance criteria specified in the method for the
selected analytical lines.
In order to accurately matrix match, it is necessary to know the concentration of all elements in the sample (to
the nearest percent). To this end, it may be necessary to carry out a preliminary analysis of the sample by
some semi-quantitative method.
4 Reagents
During the analysis, unless otherwise stated, use only reagents of recognised analytical grade and only
grade 2 water, as specified in ISO 3696.
4.1 Hydrofluoric acid, HF, 40 % (m/m), ρ approximately 1,14 g/ml.
4.2 Hydrochloric acid, HCl, ρ approximately 1,19 g/ml.
4.3 Nitric acid, HNO , ρ approximately 40 g/ml.
3
4.4 Phosphoric acid, H PO , ρ approximately 1,70 g/ml, diluted 1 + 1.
3 4
4.5 Perchloric acid, HClO , ρ approximately 1,54 g/ml, diluted 1 + 1.
4
4.6 Fuming acid mixture, mix 100 ml of the phosphoric acid (4.4) and 300 ml of the perchloric acid (4.5).
4.7 Internal standard solution, 1 000 mg/l.
Choose a suitable element to be added as internal standard and prepare a 1 000 mg/l solution. The internal
standard chosen shall
 be pure,
 not be present in the sample, and
 not interfere with analytical wavelengths, nor should the internal standard element wavelength be
interfered with by elements in the test solution.
The internal standard shall be soluble in the acids used and it shall not cause precipitation. Moreover, the
excitation conditions of the analytical line and the internal standard element line should match.
4.8 Niobium stock standard solution, 1 000 mg/l.
Weigh, to the nearest 0,000 1 g, 0,5 g of high purity niobium [min 99,95 % (mass fraction)] and dissolve in a
mixture of 30 ml hydrofluoric acid (4.1) and 3 ml nitric acid (4.3). Cool and transfer the solution quantitatively
to a calibrated 500 ml one-mark plastic volumetric flask. Dilute to the mark with water and mix. 1 ml of this
solution contains 1 mg of Nb.
NOTE It is not permitted to use pre-prepared niobium standard solutions supplied by second parties.
4.9 Niobium standard solution, 100 mg/l.
Transfer, with a calibrated pipette, 25 ml of the niobium stock standard solution (4.8) into a calibrated 250 ml
one-mark plastic volumetric flask. Add 2,5 ml of hydrofluoric acid (4.1). Dilute to the mark with water and mix.
1 ml of this solution contains 0,1 mg of Nb.
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ISO 13899-2:2005(E)
4.10 Niobium standard solution, 10 mg/l.
Transfer, with a calibrated pipette, 2,5 ml of the niobium stock standard solution (4.8) into a calibrated 250 ml
one-mark plastic volumetric flask. Add 2,5 ml of hydrofluoric acid (4.1). Dilute to the mark with water and mix.
1 ml of this solution contains 0,01 mg of Nb.
4.11 Standard solutions of interfering and matrix elements.
Prepare standard solutions for each element above 1 % (mass fraction) in the test sample. Use pure elements
or oxides with niobium contents less than 10 µg/g (mass fraction). Commercial certified standard solutions can
also be used if the niobium content is less than the value specified above.
NOTE If a large amount of an element is to be added (e.g. iron), it might be more advantageous to use the pure
metal and weigh the correct amount (see 7.3 and 7.4). In this case, use the dissolution procedure described in 7.1.2.
5 Apparatus
As it, for obvious reasons, is impossible to use volumetric glassware in this application, the laboratory has to
make sure that the plastic pipettes and flasks to be used are calibrated in accordance with ISO 648 or
ISO 1042 as appropriate.
Ordinary laboratory apparatus and
5.1 Atomic emission spectrometer, equipped with an inductively coupled plasma (ICP) and a
nebulization system resistant to hydrofluoric acid.
When a teflon nebulizer is used, it is recommended that a surface active agent should be added to improve
wetting in the nebulizer and spray chamber. Modern nebulizers are, however, often manufactured in plastic
materials with better wetting-characteristics than Teflon and can therefore (as is the case with sapphire
nebulizers) be used without a surface active agent.
The ICP-ES spectrometer used will be satisfactory if, after optimising according to 7.2.1 to 7.2.4, it meets the
performance criteria given in 5.1.2 to 5.1.4.
The spectrometer can be either the simultaneous or the sequential type. A sequential type can be used either
with or without an internal standard. However, if a sequential spectrometer is to be used with an internal
standard, it shall be fitted with an arrangement which allows for the simultaneous measurement of the internal
standard line.
5.1.1 Analytical lines
This standard does not specify any particular emission line. It is mandatory that each laboratory carefully
investigate the line/lines available on its own equipment to find the most suitable one regarding sensitivity and
freedom from interferences.
In Table 1, however, two suggestions are given together with possible interferences. These lines have been
carefully investigated (see Annex B).
The line for the internal standard element should be selected according to 4.7. It is, however, recommended to
use Sc 363.07 nm. This line is interference free for the elements and concentrations given in Annex B.
Table 1 — Examples of analytical lines together with interfering elements
Wavelength
Possible
Element
interferences
nm
Nb 309,41 V, Cr, Ni
Nb 316,34 Fe, Cr, V, W, Ti
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ISO 13899-2:2005(E)
5.1.2 Minimum practical resolution of the spectrometer
Calculate the bandwidth, according to Clause A.1, for the wavelength used including the line for the internal
standard. The bandwidth shall be less than 0,030 nm.
5.1.3 Minimum short-term precision
Calculate the short-term precision according to Clause A.2. The relative standard deviation shall not exceed
0,5 % of the mean absolute or ratioed intensities for concentrations 100 to 1 000 times the LOD (6.1.4) mg/l.
For concentrations 10 to 100 times the
...