International Standard 5663

INTERNATIONAL ORGANIZATION FOR STANDARDIZATlON.MEIK,QYHAPOfiHAFI OPrAHM3A~MR IlO CTAH~APTM3Al@lM.ORGANlSATlON INTERNATIONALE DE NORMALISATION

Water quality - Determination of Kjeldahl nitrogen -

Method after mineralization with selenium
Qua/it& de l’eau - Dosage de l azote Kjeldahl - Mb thode aprks min&alisa tion au s&nium

First edition - 1984~05-m iTeh STANDARD PREVIEW

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ISO 5663:1984
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6beeb1242799/iso-5663-1984

UDC 543.34 Ref. No. IS0 5663-1984 (E)

Descriptors : water, quality, chemical analysis, determination of content, nitrogen, Kjeldahl method, water pollution.

Price based on 4 pages

Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of
national standards bodies (IS0 member bodies). The work of developing International
Standards is carried out through IS0 technical committees. Every member body
interested in a subject for which a technical committee has been authorized 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.

Draft International Standards adopted by the technical committees are circulated to

the member bodies for approval before their acceptance as International Standards by
the IS0 Council.

International iTeh STANDARD PREVIEW

Standard IS0 5663 was developed by Technical Committee ISO/TC 147,
Water quality, and was circulated to the member bodies in December 1982.
(standards.iteh.ai)
It has been approved by the member bodies of the following countries:
ISO 5663:1984
Australia https://standards.iteh.ai/catalog/standards/sist/bcb295f6-ad2a-4871-92be-
Germany, F. R. Norway
Austria Hungary 6beeb1242799/iso-5663-1984
Poland
Belgium India Romania
Brazil Iran South Africa, Rep. of
Canada Iraq Spain
China Italy Sweden
Czechoslovakia Korea, Dem. P. Rep. of Switzerland
Denmark Mexico Thailand
Egypt, Arab Rep. of Netherlands USSR
France New Zealand

The member bodies of the following countries expressed disapproval of the document
on technical grounds :

Japan
United Ki ngdom

0 International Organization for Standardization, 1984

Printed in Switzerland
 INTERNATIONAL STANDARD IS0 5663-1984 (E)

Water quality - Determination of Kjeldahl nitrogen -

Method after mineralization with selenium

1 Scope and field of application Kjeldahl nitrogen: The content of organic nitrogen and am-
moniacal nitrogen in a sample determined after mineralization.
1 .I Substance determined
It does not include nitrate and nitrite nitrogen, and does not
This International Standard specifies a method for the deter- necessarily include all organically bound nitrogen.
mination of nitrogen by a Kjeldahl-type method. Only trivalent
negative nitrogen is determined. Organic nitrogen in the form
of azide, azine, azo, hydrazone, nitrite, nitro, nitroso, oxime or 4 Principle
semicarbazone is not determined quantitatively. Nitrogen may
be incompletely recovered from heterocyclic nitrogen com- Mineralization of the sample to form ammonium sulfate, from
pounds. which ammonia is liberated and distilled for subsequent deter-
mination by titration.

1.2 Type of sample iTeh STANDARD PREVIEW Conversion of the nitrogen compounds responding to the test
to ammonium sulfate by mineralization of the sample with
This method is applicable
waste waters.
(standards.iteh.ai)
to the analysis of raw, potable and
sulfuric acid, containing a high concentration of potassium
sulfate in order to raise the boiling point of the mixture, in the

1.3 Range
ISO 5663:1984presence of selenium which acts as a catalyst. 1)
https://standards.iteh.ai/catalog/standards/sist/bcb295f6-ad2a-4871-92be-
Liberation of ammonia from the ammonium sulfate by the addi-
A Kjeldahl nitrogen content, @N, of up to IO mg, 6beeb1242799/iso-5663-1984
in the test por- tion of alkali and distillation into boric acid/indicator solution.
tion may be determined. Using a IO ml test portion, this cor-
responds to a sample concentration of up to @N = I 000 mg/l.
Determination of ammonium ion in the distillate by titration
with standard acid.
1.4 Limit of detection
Alternatively, direct determination of ammonium ion in the
A practically determined (4 degrees of freedom) limit of detec- mineralizate by spectrometry at 655 nm. (See clause I I .)
tion, using a 100 ml test portion, is ,oN = 1 mg/l.

1.5 Sensitivity 5 Reagents

Using a 100 ml test portion, I,0 ml of 0,02 mol/l hydrochloric During the analysis, use only reagents of recognized analytical
acid is equivalent to @N = 2,8 mg/l. grade, and only distilled water prepared as described in 5.1.

5.1 Water, ammonium-free, prepared by one of the follow-

2 Reference ing methods.

IS0 71501 I, Water quality - Determination of ammonium -

Part 7: Manual spectrometric method. 5.1.1 Ion exchange method

Pass distilled water through a column of strongly acidic cation

3 Definition exchange resin (in the hydrogen form) and collect the eluate in
a glass bottle provided with a well-fitting glass stopper. Add
For the purpose of this International Standard, the following about IO g of the same resin to each litre of collected eluate for
definition applies : storage purposes.

1) Selenium has been selected as the catalyst in preference to mercury because of concern in many countries about the toxicity of mercury.
However, the toxicity of selenium must not be overlooked. See 11.2 for a suggested procedure for removal of selenium from mineralization residues.

1
IS0 5663-1984 (El

5.1.2 Distillation method 5.8 Catalyst mixture.

Add 0,lO +_ 0,Ol ml of sulfuric acid (5.3) to 1 000 +_ 10 ml of WARNING - This mixture is toxic. Inhalation of any dust
distilled water and redistil in all glass apparatus. Discard the resulting from its preparation or use shall be avoided. All
first 50 ml of distillate, and then collect the distillate in a g!ass residues containing selenium shall be collected for
bottle provided with a well-fitting glass stopper. Add about selenium recovery (11.2) or controlled disposal.
IO g of strongly acidic cation exchange resin (in the hydrogen
form) to each litre of collected distillate. Thoroughly mix 1 000 + 20 g of potassium sulfate and
10,O + 0,2 g of selenium pellets.

5.2 Hydrochloric acid, Q = 1,18 g/ml.

5.9 Anti-bumping granules.

5.3 Sulfuric acid, Q = 1,84 g/ml.

6 Apparatus
WARNING - This reagent causes severe burns.
Ordinary laboratory apparatus and :

The highest purity sulfuric acid shall always be used. Pay par-
ticular attention to the manufacturer’s specification with 6.1 Kjeldahl mineralization flasks, specially designed, of
respect to its nitrogen content. sufficient capacity to accommodate the test portion volume to
be used in the analysis, and in any event not exceeding 500 ml.

5.4 Sodium hydroxide, approximately 500 g/l solution. They should preferably be suitable for direct attachment to the
distillation apparatus (6.2).
WARNING - This reagent causes severe burns.

Dissolve 500 + 20 g of sodium

iTeh STANDARD6.2 PREVIEW
hydroxide in about 800 ml of
Distillation apparatus, incorporating an anti-splash
distillation head and a vertical condenser whose outlet can be
water. Cool to room temperature
in a measuring cylinder.
(standards.iteh.ai)
and dilute to 1 litre with water submerged in the absorbent solution.

ISO 5663:1984
5.5 Hydrochloric acid, standard https://standards.iteh.ai/catalog/standards/sist/bcb295f6-ad2a-4871-92be-
volumetric solution,
c( HCI) = 0,lO mol/l.
6beeb1242799/iso-5663-1984
NOTE ON PRELIMINARY CLEANING OF THE DISTILLATION
This solution shall be prepared by dilution of hydrochloric acid APPARATUS
(5.2) followed by standardization by normal analytical pro-
cedures. Alternatively, a commercial solution of guaranteed Carry out th e following procedure whenever the apparatus has
concentration may be used. been out of use for more than a few days.

Add about 350 ml of water (5.1) to the distillation flask. Add a

5.6 Hydrochloric acid, standard volumetric solution, few anti-bumping granules (5.9), assemble the apparatus, and
c(HCI) = 0,02 mol/l. distil at least 100 ml. Discard the distillate and the residue in the
distillation flask.
This solution shall be prepared by dilution of hydrochloric acid
(5.2 or 5.5) followed by standardization by normal analytical
procedures. Alternatively, a commercial solution of guaranteed 7 Sampling and samples
concentration may be used.
Laboratory samples shall be collected in polyethylene or glass
bottles. They should be analysed as quickly as possible, or else
5.7 Boric acid/indicator, solution. stored at between 2 and 5 OC until analysed. Acidification with
sulfuric acid (5.3) to < pH 2 may also be used as an aid to
preservation, provided that possible contamination of the
5.7.1 Dissolve 0,5 + 0,l g of methyl red in about 800 ml of
acidified sample by absorption of any atmospheric ammonia is
water and dilute to 1 litre wi th water in a measuring cylinder.
avoided.

5.7.2 Dissolve 1,5 + 0,l g of methylene blue in about 800 ml

of water and dilute to 1 litre with water in a measuring cylinder. 8 Procedure

5.7.3 Dissolve 20 + 1 g of boric acid (H3B03) in warm water. 8.1 Test portion
Cool to room temperature. Add 10 + 0,5 ml of methyl red solu-
tion (5.7.1) and 2,0 + 0,l ml of methylene blue solution (5.7.2) If the approximate nitrogen concentra tion of the sample IS
and dilute to 1 litre with water in a measuring cylinder. known I the test portion volume can be selected fro m table 1.

2
 is0 56634984 (El

Table 1 - Selection of test portion 3 0,lO mol/l hydrochloric acid (5. 51 may be used for the titration of
distillates from samples containing hi gh concentrations of nitrogen.
Kjeldahl nitrogen
Volume of the test portion*
concentration, eN I
I mg/l I ml I 9 Expression of results
up to 10 250
10 to 20 100
50
9.1 Method of calculation
20 to 50
50 to 100 25
The Kjeldahl nitrogen concentration, expressed in
* When using the 0,02 mol /I hydrochloric acid standard volumetric
milligrams per itre, is given by the formu
solution (5.6) for titration

8.2 Blank test Vl - V2

x c x 14,Ol x 1 000
Vo
Proceed as described in 8.3, but using about 250 ml of water
(5.1) instead of a test portion. Record the volume of
where
hydrochloric acid (5.6) added.

V. is the volume, in millilitres, of the test portion (see 8.1);

8.3 Determination
VI is the volume, in millilitres, of the standard volumetric
WARNING - The mineralization procedure may evolve
hydrochloric acid used for titration (see 8.3);
toxic sulfur dioxide gas. Hydrogen sulfide and/or
hydrogen cyanide may also be liberated from polluted
V2 is the volume, in millilitres, of the standard volumetric
samples. The mineralization should therefore be carried
hydrochloric acid used for the titration in the blank test (see
out under an effective fume extraction system.
8.2);
iTeh STANDARD PREVIEW
Place the test portion (8.1) in a Kjeldahl flask (6.1) and add,
c is the exact concentration, expressed in moles per litre,
from a measuring cylinder, 10 ml of sulfuric acid (5.3) and
(standards.iteh.ai)
5,0 & 0,5 g of the catalyst mixture (5.8). Add a few anti-
of the hydrochloric acid used for titration;

bumping granules (5.9) and boil the flask contents rapidly,

14,Ol is the relative atomic mass of nitrogen.
under a suitable fume extraction system. The volume ISO of 5663:1984
the
contents will decrease as water is boiled away, then evolution
https://standards.iteh.ai/catalog/standards/sist/bcb295f6-ad2a-4871-92be-
of white fumes will begin. The result may be expressed as the mass concentration of
6beeb1242799/iso-5663-1984nitrogen, eN, in milligrams per litre, or as the amount of
After fume evolution has ended, periodically observe the substance concentration of nitrogen, CN, in micromoles per
mineralizate and, after it has become clear and either colourless litre.
or light brown in colour, continue heating for a further 60 min.
(See note 1.) To convert @N to CN, multiply @N by 71,4.

After mineralization allow the flask to cool to room tempera-

ture. Meanwhile, measure 50 + 5 ml of indicator (5.7) into the 9.2 Repeatability
receiving flask of the distillation apparatus. Ensure that the
delivery tip of the condenser is below the surface of the in- Repeatability standard deviations have been determined as
dicator solution. shown in tabl e 2.

Carefully add 250 + 50 ml of water (5.1) to the mineralization

flask, together with a few anti-bumping granules (5.9). Then
10 Interferences
add, from a measuring cylinder, 50 ml of sodium hydroxide
solution (5.4) and immediately attach the flask to the distillation
apparatus. (See note 2. ) The presence of nitrate and/or nitrite may be a cause of both
negative and positive errors. Nitrate and/or nitrite may be
Heat the distillation flask so that distillate collects at a rate of reduced under the test conditions to ammonium, leading to
about 10 ml/min. Stop the distillation when about 200 ml have falsely high results. Nitrate and/or nitrite may also form am-
been collected. Titrate the distillate to a purple end-point with monium salts with ammonium in the sample. These salts may
0,02 mol/l hydrochloric acid (5.6) and record the volume be decomposed at the temperature of the mineralization,
added. (See note 3). resulting in the loss of nitrogen in gaseous forms and conse-
quently low results. If the concentration of nitrate and/or nitrite
NOTES in the sample seems likely to cause unacceptable bias or loss of
1 After water has boiled away, the rate of heating should be sufficient
precision, separate reduction to ammonium should precede the
to reflux the acid mixture half-way up the neck of the flask. This en- mineralization process.
sures the attainment of a sufficiently high mineralization temperature.

2 Where the flask is not compatible with the distillation apparatus, Falsely low results may also be obtained if the mineralization
the contents must be transferred quantitatively to a suitable distillation procedure is over-prolonged. The procedure given in clause 8
flask. This may conveniently be done at the water addition stage. must be carefully observed.

3
IS0 5663-1984 (E)

11 Notes on procedure made acid (pH 2). Reduction of this acid solution with tin(ll)
chloride (added as a solid) will produce a precipitate of red
11 .I Ammonium ion may be determined directly in the selenium which can then be filtered off and disposed of in a
mineralizate by spectrometry at 655 nm. The following pro- controlled manner.
cedure should be used.

After allowing the flask to cool following mineralization, add

50 + - 10 ml of water (5.1) to the flask. Add 2 drops of a solu-
tion of 4-nitrophenol, 1 g/l. Then, very slowly, add sodium
hydroxide solution (5.4) while thoroughly mixing and cooling
12 Test report
the solution until a pale yellow persistent colour develops. Then
add a few drops of sulfuric acid (5.3) until the yellow colour is
discharged. Transfer the solution quantitatively to a 200 ml The test report shall include the following information:
volumetric flask and dilute to volume with water (5.1). Deter-
mine ammonium ion in this solution using the spectrometric
procedure (see IS0 7150/l). Calibration and blank solutions a) a reference to this International Standard;
must be prepared by following the above procedure because
the high concentration of sodium sulfate in the neutralized b) all information necessary for complete identification of
mineralizate solution will affect the calibration of the spec- the sample;
trOmetriC procedure. The ammonium concentration, @N, ex-
pressed in milligrams per litre, determined by the spectrometric c) details of the storage and preservation of the laboratory
procedure must be multiplied by a factor 200/V. where VO is sample before analysis;
the test portion volume in millilitres (8.1), to obtain the Kjeldahl
nitrogen concentration, eN, expressed in milligrams per litre, of
d) a statement of the repeatability achieved;
the sample.

e) the results and the method of expression used;

11.2
selenium
Suggested
from
procedure
mineralization
iTeh STANDARD
for removal
residues
of
PREVIEW
f) details of any operations not included in this Inter-
The residues should be collected (standards.iteh.ai)
into a glass bottle labelled national Standard, or regarded as optional, together with
“Toxic”. For removal of selenium, the bottle contents must be any circumstance that may have affected the results.
ISO 5663:1984
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6beeb1242799/iso-5663-1984
Table 2 - Repeatability standard deviations*

Nitrogen Test portion Standard

Degrees of
Sample concentration, eN volume deviation **
freedom
mg/l ml mgll

Urea solution 2 500 0,027 19

Urea solution 50 100 0,31 19
Urea solution 150 100 2,69 19
Sewage 79 *** 50 Of68 19
Chemical waste 16 *** 200 0,19 15
Chemical waste 62 *** 100 15
04
* Data from France.

** OfI mol/l hydrochloric acid was used for all titrations, except those for the @N = 2 mg/l standard solution,
for which Of02 mol/l hydrochloric acid was used.

*** Mean value from the determinations.

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