EN ISO 11732:2005

SLOVENSKI STANDARD
01-julij-2005
Nadomešča:
SIST EN ISO 11732:1999
Kakovost vode - Določevanje amonijevega dušika – Metoda s pretočno analizo
(CFA in FIA) in spektrometrijsko detekcijo (ISO 11732:2005)
Water quality - Determination of ammonium nitrogen - Method by flow analysis (CFA and
FIA) and spectrometric detection (ISO 11732:2005)
Wasserbeschaffenheit - Bestimmung von Ammoniumstickstoff - Verfahren mittels
Fließanalytik (CFA und FIA) und spektrometrischer Detektion (ISO 11732:2005)
Qualité de l'eau - Dosage de l'azote ammoniacal - Méthode par analyse en flux (CFA et
FIA) et détection spectrométrique (ISO 11732:2005)
Ta slovenski standard je istoveten z: EN ISO 11732:2005
ICS:
13.060.50 Preiskava vode na kemične Examination of water for
snovi chemical substances
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 11732
NORME EUROPÉENNE
EUROPÄISCHE NORM
February 2005
ICS 13.060.50 Supersedes EN ISO 11732:1997
English version
Water quality - Determination of ammonium nitrogen - Method
by flow analysis (CFA and FIA) and spectrometric detection
(ISO 11732:2005)
Qualité de l'eau - Dosage de l'azote ammoniacal - Méthode Wasserbeschaffenheit - Bestimmung von
par analyse en flux (CFA et FIA) et détection Ammoniumstickstoff - Verfahren mittels Fließanalytik (CFA
spectrométrique (ISO 11732:2005) und FIA) und spektrometrischer Detektion (ISO
11732:2005)
This European Standard was approved by CEN on 3 January 2005.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 11732:2005: E
worldwide for CEN national Members.

Foreword
This document (EN ISO 11732:2005) has been prepared by Technical Committee ISO/TC 147
"Water quality" in collaboration with Technical Committee CEN/TC 230 "Water analysis", the
secretariat of which is held by DIN.

This European Standard shall be given the status of a national standard, either by publication of
an identical text or by endorsement, at the latest by August 2005, and conflicting national
standards shall be withdrawn at the latest by August 2005.

This document supersedes EN ISO 11732:1997.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

Endorsement notice
The text of ISO 11732:2005 has been approved by CEN as EN ISO 11732:2005 without any
modifications.
INTERNATIONAL ISO
STANDARD 11732
Second edition
2005-02-01
Water quality — Determination of
ammonium nitrogen — Method by flow
analysis (CFA and FIA) and spectrometric
detection
Qualité de l'eau — Dosage de l'azote ammoniacal — Méthode par
analyse en flux (CFA et FIA) et détection spectrométrique

Reference number
ISO 11732:2005(E)
©
ISO 2005
ISO 11732:2005(E)
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ii © ISO 2005 – All rights reserved

ISO 11732:2005(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
2 Normative references . 1
3 Determination of ammonium nitrogen by flow injection analysis (FIA) and spectrometric
detection . 1
4 Determination of ammonium nitrogen by continuous flow analysis (CFA) and
spectrometric detection . 7
5 Calculation. 10
6 Precision . 10
7 Test report . 11
Annex A (informative) Examples of flow analysis systems . 12
Annex B (informative) Precision data. 16
Bibliography . 18

ISO 11732:2005(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 11732 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2, Physical,
chemical and biochemical methods.
This second edition cancels and replaces the first edition (ISO 11732:1997), which has been technically
revised.
iv © ISO 2005 – All rights reserved

ISO 11732:2005(E)
Introduction
Methods using flow analysis are automating wet chemical procedures and are therefore particularly suitable
for the processing of large sample series at a high analysis frequency (up to 100 samples per hour).
[1],[2] [3]
It is differentiated between flow injection analysis (FIA) and continuous flow analysis (CFA) . Both methods
consist of the automatic dosage of the sample introduced into a flow system (manifold) in which the sample
analytes react with the reagent solutions on their way through the manifold. The sample preparation may be
integrated into the manifold. The reaction product is measured in a flow detector.
The user should be aware that particular problems could require the specification of additional marginal
conditions.
INTERNATIONAL STANDARD ISO 11732:2005(E)

Water quality — Determination of ammonium nitrogen —
Method by flow analysis (CFA and FIA) and spectrometric
detection
WARNING — Persons using this International Standard should be familiar with normal laboratory
practice. This International Standard does not purport to address all of the safety problems, if any,
associated with its use. It is the responsibility of the user to establish appropriate safety and health
practices and to ensure compliance with any national regulatory conditions.
IMPORTANT — It is absolutely essential that tests conducted according to this standard be carried
out by suitably trained staff.
1 Scope
This International Standard specifies methods suitable for the determination of ammonium nitrogen in various
types of waters (such as ground, drinking, surface, and waste waters) in mass concentrations ranging from
0,1 mg/l to 10 mg/l (in the undiluted sample), applying either FIA (Clause 3) or CFA (Clause 4). In particular
cases, the range of application may be adapted by varying the operating conditions.
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 3696:1987, Water for analytical laboratory use — Specification and test methods
ISO 5667-1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes
ISO 5667-2, Water quality — Sampling — Part 2: Guidance on sampling techniques
ISO 5667-3, Water quality — Sampling — Part 3: Guidance on the preservation and handling of water
samples
ISO 8466-1, Water quality — Calibration and evaluation of analytical methods and estimation of performance
characteristics — Part 1: Statistical evaluation of the linear calibration function
3 Determination of ammonium nitrogen by flow injection analysis (FIA) and
spectrometric detection
3.1 Principle
The sample containing ammonium is injected into a continuous carrier stream by means of an injection valve
and is mixed with a continuously streaming flow of an alkaline solution. The ammonia formed is separated in a
diffusion cell from the solution over a hydrophobic semipermeable membrane and taken up by a streaming
recipient flow containing a pH indicator. Due to the resulting pH shift, the indicator solution will change its
colour which is measured continuously in the flow photometer. Additional information about this analytical
technique is given in references [4], [5], [6], [7] and [8].
NOTE Equipment following this principle using CFA instead of FIA is commercially available, however it has not been
validated.
ISO 11732:2005(E)
3.2 Interferences
Volatile amines, if present, diffuse through the membrane and lead to a pH shift. If the concentrations of the
volatile amines (e.g. methylamine or ethylamine) are equal to those of the ammonium, higher results may then
[12]
be expected . Significant concentrations of volatile amines can be reduced by distilling the sample adjusted
to pH 5,8 prior to the analysis.
In rare cases, it may be possible that the sample does not reach a pH of 12 after the addition of the alkaline
reagent solution, thus leading to a loss of ammonium because it will not be converted quantitatively into
ammonia. This may particularly occur with strong acidic or buffered samples. In these cases, the pH of the
sample shall be adjusted to the range of 3 to 5 by the addition of sodium hydroxide solution (3.3.2 or 3.3.3).
A high concentration of metal ions that can precipitate as hydroxides will give poorly reproducible results. The
addition of a suitable complexing agent, such as ethylenedinitrilotetraacetic acid (EDTA), disodium salt, to the
alkaline reaction solution (3.3.17) in sufficiently large concentration will prevent the interference by Cu, Zn, Fe,
Ca, Mg, and Al. A concentration of 30 g/l of ethylenedinitrilotetraacetic acid, disodium salt (3.3.4), in
solution R1 (3.3.17) is adequate for metal concentrations up to 0,2 mg/l each.
In the case of samples containing particulate matter, see 3.5 (last paragraph).
Samples with a total salt concentration of > 10 g/l shall be diluted prior to the measurement.
3.3 Reagents
Apart from the reagents dealt with in the 3.3.6 and 3.3.7, use only reagents of “analytical grade quality for the
determination of nitrogen”, or, if not available, those of recognized “analytical grade quality”. The ammonium
content of the blank shall regularly be checked (3.6.3).
3.3.1 Water, of grade 1 as specified in ISO 3696:1987.
3.3.2 Sodium hydroxide solution I, c(NaOH) = 5 mol/l.
3.3.3 Sodium hydroxide solution II, c(NaOH) = 0,01 mol/l.
1)
3.3.4 Ethylenedinitrilotetraacetic acid (EDTA) , disodium salt, monohydrate, C H N Na O ⋅H O.
10 14 2 2 8 2
3.3.5 Bromocresol purple, C H Br O S.
21 16 2 5
3.3.6 Bromothymol blue, C H Br O S.
27 28 2 5
3.3.7 Cresol red, C H O S.
21 18 5
3.3.8 Ammonium chloride, NH Cl, dried at 105 °C ± 2 °C to constant mass.
3.3.9 Potassium chloride, KCl.
3.3.10 Boric acid, H BO .
3 3
3.3.11 Hydrochloric acid solution I, c(HCl) = 0,01 mol/l.
3.3.12 Hydrochloric acid solution II, c(HCl) = 0,1 mol/l.
3.3.13 Hydrochloric acid solution III, c(HCl) = 1,0 mol/l.
3.3.14 Sulfuric acid, ρ(H SO ) = 1,84 g/ml.
2 4
1) Commonly known as ethylenediaminetetraacetic acid.
2 © ISO 2005 – All rights reserved

ISO 11732:2005(E)
3.3.15 Mixed indicator.
In a mortar prepare a dry mixture consisting of 10 g of bromocresol purple (3.3.5), 5 g of bromothymol blue
(3.3.6), 2,5 g of cresol red (3.3.7), and 45 g of potassium chloride (3.3.9).
The given quantities can be reduced (e.g. by one tenth).
3.3.16 Carrier solution, C (see Figure A.1).
Use water according to 3.3.1, degassed e.g. by reduced pressure.
3.3.17 Alkaline reaction solution, R1 (see Figure A.1).
Dissolve in a graduated flask, nominal capacity 1 000 ml, 30 g of ethylenedinitrilotetraacetic acid, disodium
salt (3.3.4) in approximately 800 ml of water (3.3.1), and add 12,4 g of boric acid (3.3.10).
Add 100 ml of sodium hydroxide solution I (3.3.2) dropwise to the suspension and make up to volume with
water (3.3.1).
Degas the solution by filtering it through the membrane filter assembly (3.4.2).
The pH of the solution will be approximately 13. Being stored in a plastics bottle (polyethene) at room
temperature, it will be stable for one month.
3.3.18 Indicator solution.
Dissolve in a 200 ml graduated flask 1 g of the mixed indicator (3.3.15) in a mixture of 50 ml of sodium
hydroxide solution II (3.3.3). Make up to volume with water (3.3.1).
The solution should have a dark reddish colour.
Filter off any undissolved particles.
This solution may be stored at room temperature for three months in an amber glass bottle.
3.3.19 Ammonia recipient solution, R2 (see Figure A.1).
Dilute 10 ml of the indicator solution (3.3.18) with approximately 480 ml of water (3.3.1).
The absorbance of the solution should be 0,3 to 0,5. Otherwise, add dropwise sodium hydroxide solution II
(3.3.3) or hydrochloric acid solution III (3.3.13) until an absorbance value of 0,3 to 0,5 (path length 10 mm,
wavelength 590 nm) is obtained. Make up to 500 ml with water (3.3.1).
Degas and purify the solution by the membrane filter assembly (3.4.2), fill it into the reagent reservoir and let it
stand for at least 2 h.
Immediately before starting the measurement (3.6), check the absorbance again and adjust, if need be, to the
absorbance range specified above by adding sodium hydroxide solution II (3.3.3) or hydrochloric acid I, II or III
(3.3.11 to 3.3.12) respectively.
This solution may be stored at room temperature for two weeks in a glass bottle.
3.3.20 Ammonium stock solution, ρ(N) = 1 000 mg/l.
Dissolve in a 1 000 ml graduated flask 3,819 g of ammonium chloride (3.3.8) in approximately 900 ml of water
(3.3.1), acidify to pH 2 by dropwise addition of sulfuric acid (3.3.14), and make up to volume with water (3.3.1).
This solution may be stored in a refrigerator for at most three months.
ISO 11732:2005(E)
3.3.21 Ammonium standard solution I, ρ(N) = 100 mg/l.
Pipette 10 ml of the ammonium stock solution (3.3.20) into a 100 ml graduated flask, add approximately 80 ml
of water (3.3.1), acidify by dropwise addition of sulfuric acid (3.3.14), and make up to volume with water
(3.3.1).
This solution may be stored in a refrigerator for at most one week.
3.3.22 Ammonium standard solution II, ρ(N) = 10 mg/l.
Pipette 1 ml of the ammonium stock solution (3.3.20) or 10 ml of the ammonium standard solution I (3.3.21)
into a 100 ml graduated flask, add approximately 80 ml of water, acidify to pH 2 by dropwise addition of
sulfuric acid (3.3.14), and make up to volume with water (3.3.1).
This solution may be stored in a refrigerator for at most one week.
3.3.23 Calibration solutions
Prepare calibration solutions by diluting the ammonium standard solutions I or II (3.3.21 or .3.3.22). At least
five calibration standards per working range are recommended. As an example, if six standards are applied,
proceed for the working ranges I or II respectively, as follows:
a) Working range I (1 mg/l to 10 mg/l):
 Pipette into a series of 100 ml graduated flasks, 1 ml, 2 ml, 4 ml, 6 ml, 8 ml and 10 ml respectively, of the
ammonium standard solution I (3.3.21), and make up to volume with water (3.3.1).
 The mass concentrations of ammonium, expressed as nitrogen, in these calibration solutions are 1 mg/l,
2 mg/l, 4 mg/l, 6 mg/l, 8 mg/l and 10 mg/l.
b) Working range II (0,1 mg/l to 1,0 mg/l):
 Pipette into a series of 100 ml graduated flasks, 1 ml, 2 ml, 4 ml, 6 ml, 8 ml and 10 ml respectively, of the
ammonium standard solution II (3.3.22), and make up to volume with water (3.3.1).
 The mass concentrations of ammonium, expressed as nitrogen, in these calibration solutions are 0,1 mg/l,
0,2 mg/l, 0,4 mg/l, 0,6 mg/l, 0,8 mg/l and 1,0 mg/l.
Prepare all calibration solutions freshly before use.
3.4 Apparatus
3.4.1 Flow injection system.
In general, the flow injection system consists of the following components (see Figure A.1).
3.4.1.1 Reagent reservoirs.
3.4.1.2 Low pulsation pump.
3.4.1.3 Suitable pump tubes, if required.
3.4.1.4 Injection valve with a suitable injection volume.
For working range I, an injection volume of 40 µl, for working range II, a volume of e.g. 360 µl or 400 µl is
recommended.
4 © ISO 2005 – All rights reserved

ISO 11732:2005(E)
3.4.1.5 Diffusion cell with hydrophobic semipermeable membrane (e.g. made from
polytetrafluoroethene, PTFE).
EXAMPLES
thickness of membranes: 150 µm to 200 µm;
pore size: 0,5 µm to 2,0 µm;
porosity: 75 %.
3.4.1.6 Transport tubes and reaction coils, having an internal diameter of 0,5 mm to 0,8 mm, tube
connections and T-connections of inert plastic and with minimum dead volumes.
3.4.1.7 Photometric detector with flow cell, having a normal path length of 10 mm to 50 mm and a
wavelength range 580 nm to 600 nm.
3.4.1.8 Recording unit (e.g. strip chart recorder, integrator or printer/plotter), generally used for
evaluation of peak height signals.
3.4.1.9 Autosampler, if required.
3.4.2 Additional apparatus.
Usual laboratory apparatus and the following.
3.4.2.1 Graduated flasks, of 100 ml, 200 ml and 1 000 ml capacities.
3.4.2.2 Graduated pipettes, of 1 ml to 10 ml capacities.
3.4.2.3 Membrane filter assembly with membrane filters, having a pore size of 0,45 µm.
3.5 Sampling and sample pretreatment
Take samples in accordance w
...