tional Standard 6777

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION~MEX~YHAPO~HAFI OPTAHM3AUMfl l-i0 CTAHAAPTM3Ae(MM*ORGANlSATlON INTERNATIONALE DE NORMALISATION

Water quality - Determination of nitrite - Molecular

absorption spectrometric method
Qualit de l eau - Dosage des nitrites - Mthode par spectromktrie d/absorption moltkulaire

First edition - 1984-08-01

iTeh STANDARD PREVIEW
(standards.iteh.ai)
ISO 6777:1984
https://standards.iteh.ai/catalog/standards/sist/10531135-72d2-487d-
9471-410717fbf14f/iso-6777-1984

UDC 543.344 : 543.42 Ref. No. IS0 677-1984 (E)

Descriptors : water, chemical analysis, determination of content, nitrites, spectrometric analysis.

Price based on 5 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 6777 was developed by Technical Committee ISO/TC
Water quality, and was circulated to the member bodies in December 1982.
147,

It has been approved by the member

(standards.iteh.ai)
bodies of the following countries:

Australia
ISO 6777:1984
Hungary Poland
Austria https://standards.iteh.ai/catalog/standards/sist/10531135-72d2-487d-
India Romania
Belgium Iran 9471-410717fbf14f/iso-6777-1984
South Africa, Rep. of
Brazil Iraq Spain
Canada Italy Sweden
Czechoslovakia Japan Switzerland
Denmark Korea, Dem. P. Rep. of Thailand
Egypt, Arab Rep. of Mexico United Kingdom
China Netherlands USSR
France New Zealand
Germany, F. R. Norway

No member body expressed disapproval of the document.

0 International Organization for Standardization, 1984

Printed in Switzerland
 INTERNATIONAL STANDARD IS0 6777-1984 (E)

Water quality - Determination of nitrite - Molecular

absorption spectrometric method

I Scope 3 Principle

This International Standard specifies a molecular absorption Reaction of nitrite in the test portion with 4-aminobenzene
spectrometric method for the determination of nitrite in sulfonamide reagent in the presence of orthophosphoric acid at
potable, raw and waste water. pH 1,9 to form a diazonium salt which forms a pink-coloured
dye with IV-( I-naphthylj-1,2-diaminoethane dihydrochloride
(added with the 4-aminobenzene sulfonamide reagent).
Measurement of the absorbance at 540 nm.
2 Field of application

4 Reagents
2.1 Range
During the analysis, use only reagents of recognized analytical
A nitrite nitrogen concentration, &)N, of up to 0,25 mg/l can be grade and only distilled water or water of equivalent purity.
determined
portion. iTeh STANDARD4.1PREVIEW
when using the maximum volume (40 ml) of test
Orthophosphoric acid, 15 mol/l solution,

2.2 Limit of detection 1)

(standards.iteh.ai) (Q = I,70 g/ml).

4.2 Orthophosphoric acid, approximately 1,5 mol/l solu-

When using cells of optical path length 40 mm and a test ISOpor-
6777:1984tion.
https://standards.iteh.ai/catalog/standards/sist/10531135-72d2-487d-
tion of 40 ml, the limit of detection has been determined to lie
within the range @N = 0,001 to 0,002 mg/l. 9471-410717fbf14f/iso-6777-1984
Add, by means of a pipette, 25 ml of the orthophosphoric acid
(4.1) to 150 + 25 ml of water. Mix and cool to room
temperature. Transfer the solution to a 250 ml one-mark
2.3 Sensitivity 1) volumetric flask and dilute to the mark with water.

Using a 40 ml test portion and a cell of optical path length Store in an amber glass bottle. The solution is stable for at least
4. mm, eN = 0,062 mg/l gives an absorbance of about 6 months.
0,66 units.
4.3 Colour reagent.
Using a 40 ml test portion and a cell of optical path length
10 mm, eN = 0,25 mg/l gives an absorbance of about WARNING - This reagent is hazardous. Skin contact or
0,67 units. ingestion of it or its ingredients must be avoided.

Dissolve 40,O + 0,5 g of 4-aminobenzene sulfonamide

2.4 Interferences (NH,CGH,S02NH2) in a mixture of 100 rt 1 ml of the or-
thophosphoric acid (4.1) and 500 & 50 ml of water in a beaker.
If the alkalinity of the sample is high, some interference may be
encountered (see clause 9). Dissolve 2,00 + 0,02 g of IV-( I-naphthyl)-1,2-diaminoethane
dihydrochloride K,,H,-NH-CH,-CH,-NH2.2HCl) in the
A range of substances often encountered in water samples has resulting solution. Transfer to a 1 000 ml one-mark volumetric
been tested for possible interference. Full details are given in flask and dilute to the mark with water. Mix well.
the annex. Of the substances tested, only chloramine, chlorine,
thiosulfate, sodium polyphosphate and iron(lll) interfere Store in an amber glass bottle. The solution is stable for 1
significantly. month if stored at 2 to 5 OC.

1) Information derived from a United Kingdom interlaboratory trial involving five participants.
IS0 6777-1984 (El

4.4 Nitrite, standard solution, @N = 100 mg/l. Add, by means of a pipette, I,0 ml of the colour reagent (4.3).
Mix immediately by swirling and dilute to the mark with water.
Dissolve 0,492 2 + 0,000 2 g of sodium nitrite (dried at 105 OC Mix and allow to stand. The pH at this stage should be
for at least 2 h) in about 750 ml of water. Transfer quantitatively I,9 + 0,l. (See clause 9.)
to a 1 000 ml one-mark volumetric flask and dilute to the mark
with water. At least 20 min after addition of the reagent, measure the ab-
sorbance of the solution at the wavelength of maximum absor-
Store in a stoppered amber glass bottle at 2 to 5 OC. This solu- bance, approximately 540 nm, in a cell of suitable optical path
tion is stable for at least 1 month. (See clause IO.) length, using water as the reference liquid.

NOTE - The wavelength of maximum absorbance should be checked

4.5 Nitrite, standard solution, eN = I,00 mg/l. when this method is first used, and should be used in all subsequent
determinations.
Transfer, by means of a pipette, 10 ml of the standard nitrite
solution (4.4) to a 1 000 ml one-mark volumetric flask and dilute
7.3 Correction for colour
to the mark with water.

If the colour of the test portion is such that it may interfere with
Prepare this solution each day as required, and discard after
the measurement of absorbance, treat a duplicate test portion
use.
as described in 7.2, but replacing the colour reagent (4.3) with
I,0 ml of the orthophosphoric acid solution (4.2).

5 Apparatus
7.4 Blank test
All glassware shall be carefully cleaned using approximately
2 mol/l hydrochloric acid and then rinsed thoroughly with Carry out a blank test by proceeding as described in 7.2, but
water. replacing the test portion with 40 fr 2 ml of water.

Ordinary laboratory apparatus, and 7.5 Preparation of the calibration graph

iTeh STANDARD PREVIEW Place, by means of a burette, into a series of nine 50 ml one-
Spectrometer, suitable for measurements at a wavelength of
540 nm, together with cells of optical path length between (standards.iteh.ai) 10 mark volumetric flasks, the volumes of the standard nitrite solu-
tion (4.5) shown in table 1.
and 50 mm.
ISO 6777:1984
Dilute the contents of each flask with water to give a volume of
https://standards.iteh.ai/catalog/standards/sist/10531135-72d2-487d-
40 + 2 ml and proceed as described in 7.2, from the second
6 Sampling and samples 9471-410717fbf14f/iso-6777-1984
paragraph to the end, using cells of optical path length
specified in table 1.
Laboratory samples should be collected in glass bottles and
should be analysed as soon as possible within 24 h of collec-
Subtract the absorbance of the zero term from the absorbances
tion. Storage of the samples at 2 to 5 OC may preserve many
obtained for the other standard solutions and plot a graph of
types of sample, but this should be verified.
absorbance against the mass of nitrite, as nitrogen, for each
optical path length. The graph should be linear and should pass
through the origin.
7 Procedure

7.1 Test portion 8 Expression of results

The maximum volume of test portion is 40 ml. This is suitable
8.1 Method of calculation
for the determination of nitrite concentrations of up to
QN = 0,25 mg/l. Smaller test portions may be used as ap-
The corrected absorbance, A,, of the test solution is given by
propriate in order to accommodate much higher nitrite concen-
the equation
trations. If the laboratory sample contains suspended matter,
this should be allowed to settle, or the sample should be filtered
A, = A, - A,
through a glass fibre paper before taking the test portion.
or, if correction for colour was made, by means of the equation ,
7.2 Determination A, = A, - A, - A,
Transfer, by means of a pipette, the selected volume of test
portion to a 50 ml one-mark volumetric flask, and, if necessary,
dilute to 40 + 2 ml with water. A, is the absorbance, as measured, of the test solution;

Ab is the absorbance of the blank test solution

NOTE - It is always essential to adjust the volume to 40 + 2 ml to en-
sure that the correct pH is obtained (after addition of the reagent) for
AC is the absorbance of the solution prepared for the cor-
the reaction. rection for colour.
 IS0 67774984 (El

NOTE - It is essential that the values of A,, A, and A, are measured in amount of substance concentration of nitrite ion, c(NO& in
cells of the same optical path length for a particular sample. micromoles per litre. The appropriate conversion factors are
given in table 2.
From the corrected absorbance A,, determine from the calibra-
tion graph (7.5), for the appropriate optical path length of the Table 2
cell, the corresponding mass of nitrite, as nitrogen, in
micrograms.

The nitrite content, expressed in milligrams of nitrogen per litre,

is given by the formula = 1 mg/l
@N

@NO, = 1 mg/l
PUN
C( NOi) = 1 pmol/l
V
Example:
where

A nitrogen concentration of 1 mg/l corresponds to a nitrite

!?I N is the mass, in micrograms, of nitrite nitrogen cor-
concentration of 3,29 mg/l.
responding to the corrected absorbance (A,);

V is the volume, in millilitres, of the test portion. 8.2 Precision

The result may be expressed as the mass concentration of Repeatability and reproducibility standard deviations have been
nitrogen, @N, or nitrite, @Noj, in milligrams per litre, or as the determined as indicated in table 3.

Table 1
iTeh STANDARD PREVIEW
Volume of standard
nitrite solution(standards.iteh.ai)
(4.5)
Mass of nitrite nitrogen, mN
I
Optical path length of cell

ml I I43 1
0,oo ISO 6777:1984
0,oo 10 and 40”
0,50 0,50
https://standards.iteh.ai/catalog/standards/sist/10531135-72d2-487d- 40
l,oo l,oo
9471-410717fbf14f/iso-6777-1984 IO and 40
1,513 I,50 40
2,00 2,00 40
z50 2,50 10 and 40
5m 5,00 10
7,50 7,50 10
10,oo IO,00 10
* 50 mm cells may also be used.

3
IS0 6777-1984 (E)

Table 3*

Standard solution 0,000 2 to 0,000 8 0,000 2 to 0,001 8

Standard solution 0,001 1 to 0,005 4 0,003 to 0,009

Standard solution 0,002 to 0,026 0,007 to 0,040

Sewage effluent 0,002 to 0,020 0,004 to 0,021

Sea water 0,000 3 to 0,002 6 0,001 to 0,004

* Information derived from a United Kingdom interlaboratory trial involving five participants.

** The highest and lowest values from the interlaboratory exercise. All values have 14 degrees of freedom.

9 Special cases 50 ml of a potassium permanganate standard volumetric solu-

tion, c(1/5 KMnO& = 0,Ol mol/l, is equivalent to 3,502 mg of
lf the alkalinity of the sample is high, such that the pH is not nitrogen. Thus, for the standard nitrite solution (4.41, the
I,9 + 0,l after treating test portion and diluting to 40 ml, addi- volume used in the titration should be 35,02 ml. The standard
tional orthophosphoric acid solution (4.2) should be added nitrite solution is only suitable if the volume used in the titration
before dilution, so that the specified pH is attained. The lies within the range 35,02 rt 0,40 ml.
method will, however, tolerate a hydrogen carbonate alkalinity
of at least 300 mg/l in a test portion of 40 ml without deviation
from the specified pH.
iTeh STANDARD PREVIEW
11 Test report

40 Notes on procedure
(standards.iteh.ai) The test report shall include the following information:

As standard nitrite solutions may become unstable, the con- ISO 6777:1984
centration of the standard nitrite solution (4.4) used may be a) a reference to this International Standard;
https://standards.iteh.ai/catalog/standards/sist/10531135-72d2-487d-
checked by the following method:
9471-410717fbf14f/iso-6777-1984
b) all details required for the complete identification of the
sample;
Place by means of a pipette, 50 ml of potassium permanganate
standard volumetric solution, c(1/5 KMn04) = 0,Ol mol/l, in a c) details concerning the storage of the laboratory sample
250 ml conical flask. Add 10 + 1 ml of 2,5 mol/l sulfuric acid before analysis;
solution and mix thoroughly. Fill a 50 ml burette with the stan-
dard nitrite solution (4.4) and arrange the apparatus so that the d) a statement of the repeatability achieved by the
tip of the burette dips below the surface of the acid per- laboratory when using this method;
manganate solution in the flask. Titrate to a colourless end-
e) the results and the method of expression used;
point. As the end-point approaches, warm the solution to
about 40 OC and continue the titration slowly until the colour of f) details of any deviation from the procedure specified in
the permanganate is just discharged. Note the volume of stan- this International Standard or any other circumstances that
dard nitrite solution used in the titration. may have influenced the result.

4
 IS0 6777-1984 (E)

Annex

Effect of other substances on the result

Mass of Effect** upon the determination of

Substance Salt used substance*
I-19 mN = 0 l-43 mN = I,00 pg mN = IO,0 I-Q

Magnesium Acetate 1 000 0,oo 0,oo - 0,07

Potassium Chloride 100 0,oo 0,oo - 0,07

Potassium Chloride 1 000 0,oo - 0,03 -0,13

Sodium Chloride 100 0,oo 0,oo - 0,02

Sodium Chloride 1 000 0,oo - 0,Ol -0,13

Hydrogen carbonate Sodium 6 100 (HCO,) 0,oo + 0,03 + 0,Ol

Hydrogen carbonate Sodium 12 200 (HCO,) 0,oo + 0,03 + 0,06

Nitrate Potassium 1 000 (N) 0,oo 0,oo - 0,06

Ammonium Chloride 100 (N) 0,oo - 0,Ol - 0,03

Cadmium Chloride 100 0,oo - 0,03 - 0,03

Zinc Acetate 100 0,oo - 0,04 0,oo

100 0,oo + 0,04 - 0,03

Manganese
Iron( Ill)
iTeh STANDARD PREVIEW
Chloride
Chloride 10 0,oo + 0,04 - 0,03

Iron(lll) (standards.iteh.ai)
Chloride 100 0,oo - 0,06 - 0,51

Copper Acetate 100 - 0,06 - 0,06 - 0,07

Aluminium Sulfate ISO 6777:1984

100 0,oo 0,oo - 0,03

Silicate https://standards.iteh.ai/catalog/standards/sist/10531135-72d2-487d-
Sodium 100 (SiO,) 0,oo 0,oo -
9471-410717fbf14f/iso-6777-1984
100
Urea - 0,oo + 0,04 - 0,09

Thiosulfate Sodium 100 (s,o;-) 0,oo - 0,03 - 0,82

Thiosulfate Sodium 1 000 ( s,o;-) 0,oo 0,oo - 0,77

Chlorine - 2 (Cl,) 0,oo - 0,22 - 0,25

Chlorine - 20 (Cl,) - 0,Ol - I,01 - 2,81

Chloramine - 2 (Cl,) - - 0,06 - 0,07

Chloramine - 20 (Cl,) - 0,Ol - 0,30 - 2,78

Hydroxylammonium chloride 100 0,oo 0,oo - 0,Ol

Sodium polyphosphate (hexametaphosphate) 50 0,oo - 0,03 - 0,82

Sodium polyphosphate (hexametaphosphate) 500 0,oo - 0,80 -8,lO

Mass of substance present in the test portion. The mass is given as the element or compound, except where otherwise indicated in brackets.

** The maximum effects, assuming no interference, are as follows: 0,OO IL 0,02 pg; I,00 I!I 0,08 pg; 10,OO + 0,14 pg (95 % confidence limit).

5
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