ISO 7485:2000
(Main)Animal feeding stuffs — Determination of potassium and sodium contents — Methods using flame-emission spectrometry
Animal feeding stuffs — Determination of potassium and sodium contents — Methods using flame-emission spectrometry
This International Standard specifies a calibration method and a standard addition method for the determination of potassium and sodium contents of animal feeding stuffs by flame-emission spectrometry. The standard addition method applies if it is not known whether the emissions measured for potassium or sodium are subject to matrix effects. The limit of determination for potassium and sodium is 0,04 g/kg. The calibration method applies if such matrix effects have been shown to be absent.
Aliments des animaux — Détermination des teneurs en potassium et sodium — Méthodes par spectrométrie d'émission de flamme
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 7485
First edition
2000-08-15
Animal feeding stuffs — Determination of
potassium and sodium contents —
Methods using flame-emission
spectrometry
Aliments des animaux — Détermination des teneurs en potassium et
sodium — Méthodes par spectrométrie d'émission de flamme
Reference number
ISO 7485:2000(E)
©
ISO 2000
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ISO 7485:2000(E)
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ISO 7485:2000(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
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Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
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 International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 7485 was prepared by Technical Committee ISO/TC 34, Agricultural food products,
Subcommittee SC 10, Animal feeding stuffs.
Annex A of this International Standard is for information only.
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INTERNATIONAL STANDARD ISO 7485:2000(E)
Animal feeding stuffs — Determination of potassium and sodium
contents — Methods using flame-emission spectrometry
1 Scope
This International Standard specifies a calibration method and a standard addition method for the determination of
potassium and sodium contents of animal feeding stuffs by flame-emission spectrometry.
The standard addition method applies if it is not known whether the emissions measured for potassium or sodium
are subject to matrix effects. The limit of determination for potassium and sodium is 0,04 g/kg.
The calibration method applies if such matrix effects have been shown to be absent.
2 Normative reference
The following normative document contains provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent edition of the normative document indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 6498:1998, Animal feeding stuffs — Preparation of test samples.
3Principle
The test portion is incinerated to destroy any organic matter. The potassium and sodium are dissolved by treatment
with hydrochloric acid. The potassium and sodium contents are determined by flame-emission spectrometry at
wavelengths of 766 nm and 589 nm respectively, by means of a calibration curve (calibration method) or a
standard addition graph (standard addition method).
4 Reagents
Use only reagents of recognized analytical quality.
4.1 Water, double distilled, or double deionized.
4.2 Potassium chloride (KCl), dried for 2 h at (110� 2) °C.
4.3 Sodium chloride (NaCl), dried for 2 h at (110� 2) °C.
4.4 Concentrated hydrochloric acid, c(HCl) = 12 mol/l (� (HCl) = 1,19 g/ml).
20
4.5 Hydrochloric acid, c(HCl) = 6 mol/l.
4.6 Dilute hydrochloric acid, c(HCl) = 0,1 mol/l.
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ISO 7485:2000(E)
4.7 Ionization and release buffer solution.
Dissolve 50 g of caesium chloride and 250 g of aluminium nitrate nonahydrate [Al(NO ) ����9H O] in water. Dilute to
3 3 2
1 litre with water and mix. Store in a plastic bottle, e.g. polyethene or polypropylene.
4.8 Potassium standard solutions.
4.8.1 Potassium stock solution, �(K) = 1 mg/ml.
Weigh 1,906 g of potassium chloride (4.2) and transfer to a 1 000 ml volumetric flask with approximately 250 ml of
dilute hydrochloric acid (4.6). Dissolve and dilute to the mark with the hydrochloric acid (4.6).
Store in a plastic bottle, e.g. polyethene or polypropylene. At room temperature the solution is stable for up to
6 months.
4.8.2 Potassium intermediate solution, �(K) = 100�g/ml.
Transfer 10 ml of the potassium stock solution (4.8.1) to a 100 ml volumetric flask. Dilute to the mark with dilute
hydrochloric acid (4.6) and mix.
Store in a plastic bottle, e.g. polyethene or polypropylene. At room temperature the solution is stable for 1 month.
4.8.3 Potassium calibration solution, �(K) = 10�g/ml.
Transfer 10 ml of the potassium intermediate solution (4.8.2) to a 100 ml volumetric flask. Add 10 ml of the
ionization and release buffer solution (4.7). Dilute to the mark with dilute hydrochloric acid (4.6) and mix.
Prepare fresh on the day of use.
4.9 Sodium standard solutions.
4.9.1 Sodium stock solution, �(Na) = 1 mg/ml.
Weigh 2,542 g of sodium chloride (4.3) and transfer to a 1 000 ml volumetric flask with approximately 250 ml of
dilute hydrochloric acid (4.6). Dissolve and dilute to the mark with the hydrochloric acid (4.6). Mix well.
Store in a plastics bottle. At room temperature the solution is stable for up to 6 months.
4.9.2 Sodium intermediate solution, �(Na) = 100�g/ml.
Transfer 10 ml of the sodium stock solution (4.9.1) to a 100 ml volumetric flask. Dilute to the mark with dilute
hydrochloric acid (4.6) and mix.
Store in a plastics bottle. At room temperature the solution is stable for 1 month.
4.9.3 Sodium calibration solution, �(Na) = 10�g/ml.
Transfer 10 ml of the sodium intermediate solution (4.9.2) to a 100 ml volumetric flask. Add 10 ml of the ionization
and release buffer solution (4.7). Dilute to the mark with the hydrochloric acid (4.6) and mix.
Prepare fresh on the day of use.
4.10 Biological Certified Reference Materials.
For example: V8-Rye flour or V10-Hay (powdered), from the International Atomic Energy Agency (IAEA), Austria;
SRM 157-Wheat flour, SRM 1568a-Rice flour or SRM 1548-Total diet, from the National Institute of Standards and
Technology (NIST), USA.
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ISO 7485:2000(E)
5 Apparatus
Usual laboratory equipment and, in particular, the following.
5.1 Analytical balance, capable of weighing to the nearest 1 mg.
5.2 Muffle furnace, electrically heated, capable of being maintained at (550� 20) °C.
5.3 Ashing dishes, of platinum or silica.
5.4 Flame photometer with an air-butane, air-propane or air-acetylene flame in a ratio allowing complete
combustion; or an atomic absorption spectrometer operating in emission mode and equipped to determine
potassium and sodium with an air-acetylene flame.
5.5 Sand bath or hot plate, capable of being maintained at approximately 150 °C.
5.6 TD (to deliver) precision pipettes or microburette of 5 ml capacity.
5.7 TC (to contain) precision pipettes, of various capacities.
5.8 Beakers, of 250 ml capacity.
5.9 Volumetric flasks, of various capacities.
6 Sampling
Sampling is not part of the method specified in this International Standard. A recommended sampling method is
given in ISO 6497 [1].
It is important that the laboratory receive a sample which is truly representative and has not been damaged or
changed during transport or storage.
7 Preparation of test sample
Prepare the test sample in accordance with ISO 6498.
8 Procedure
8.1 Test portion
8.1.1 Samples containing organic matter
Depending on the expected content, weigh 1 g to 5 g of the prepared test sample (clause 7) to the nearest 1 mg
into an ashing dish (5.3). Proceed in accordance with 8.2.1.
8.1.2 Samples not containing organic matter
Depending on the expected content of potassium and sodium, weigh 1 g to 5 g of the prepared test sample to the
nearest 1 mg into a beaker (5.8). Proceed in accordance with 8.2.2.
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ISO 7485:2000(E)
8.2 Preparation of test solution
8.2.1 Incineration and rendering silica insoluble
Place the incineration dish containing the test portion (8.1.1) in the cold muffle furnace (5.2). Close the furnace and
gradually increase the temperature to 550 °C and ash for 3 h at this temperature.
If many carbon particles are present, allow to cool down, moisten the contents of the dish with 2 ml of water and dry
the dish on the sand bath or hot plate (5.5). Ash for another 2 h at 550 °C in the muffle furnace.
Allow to cool down, moisten the ash with a few drops of water and transfer it to a 250 ml beaker (5.8). Rinse the
incineration dish with a total of approximately 5 ml of concentrated hydrochloric acid (4.4) and then with a few
millilitres of water, collecting the rinsings in the beaker.
CAUTION — Take care during the addition of hydrochloric acid, as an effervescent reaction may occur with
some samples.
Put a watch glass on the beaker to reduce spattering and slowly evaporate the contents of the beaker to near
dryness on the sand bath o
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