EN ISO 11732:1997
(Main)Water quality - Determination of ammonium nitrogen by flow analysis (CFA and FIA) and spectrometric detection (ISO 11732:1997)
Water quality - Determination of ammonium nitrogen by flow analysis (CFA and FIA) and spectrometric detection (ISO 11732:1997)
According to the methods specified in this document ammonia may be determined in large sample series and the high analysis frequency. The method includes an automatic dosage.
Wasserbeschaffenheit - Bestimmung von Ammoniumstickstoff mit der Fließanalysis (CFA und FIA) und spektrometrischer Detektion (ISO 11732:1997)
Diese Internationale Norm legt ein Verfahren zur Bestimmung von Ammonium- Stickstoff in unterschiedlichen Wässern fest, (wie z.B. Grund-, Trink-, Oberflächen- und Abwässer) in Massenkonzentrationen von 0,1 mg/l bis 10 mg/l (in der unverdünnten Probe). In Einzelfällen kann durch Variation der Arbeitsbedingungen der Anwendungsbereich verändert werden.
Qualité de l'eau - Détermination de l'azote ammoniacal par analyse de l'écoulement (CFA et FIA) et détection spectrométrique (ISO 11732:1997)
Kakovost vode - Določevanje amonijevega dušika s pretočno analizo (CFA in FIA) in spekrofotometrijsko detekcijo (ISO 11732:1997)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 11732:1999
01-marec-1999
.DNRYRVWYRGH'RORþHYDQMHDPRQLMHYHJDGXãLNDVSUHWRþQRDQDOL]R &)$LQ),$
LQVSHNURIRWRPHWULMVNRGHWHNFLMR ,62
Water quality - Determination of ammonium nitrogen by flow analysis (CFA and FIA) and
spectrometric detection (ISO 11732:1997)
Wasserbeschaffenheit - Bestimmung von Ammoniumstickstoff mit der Fließanalysis
(CFA und FIA) und spektrometrischer Detektion (ISO 11732:1997)
Qualité de l'eau - Détermination de l'azote ammoniacal par analyse de l'écoulement
(CFA et FIA) et détection spectrométrique (ISO 11732:1997)
Ta slovenski standard je istoveten z: EN ISO 11732:1997
ICS:
13.060.50 3UHLVNDYDYRGHQDNHPLþQH Examination of water for
VQRYL chemical substances
SIST EN ISO 11732:1999 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 11732:1999
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SIST EN ISO 11732:1999
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SIST EN ISO 11732:1999
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SIST EN ISO 11732:1999
INTER NAL IS0
STANDARD 11732
First edition
1997-07-01
Determination of
Water quality -
ammonium nitrogen by flow analysis
(CFA and FIA) and spectrometric detection
Qualit de I’eau - Determination de I’azote ammoniacal par analyse en
flux (CFA et F/A) et dbtection spectrombtrique
Reference number
IS0 11732:1997(E)
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SIST EN ISO 11732:1999
IS0 11732: 1997(E)
Foreword
lS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
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. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
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.
International Standard IS0 11732 was prepared by Technical Committee
ISORC 147, Water quality, Subcommittee SC 2, Physical, chemical and
biochemical methods.
Annexes A to D of this International Standard are for information only.
0 IS0 1997
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 l CH-1211 Geneve 20 l Switzerland
Internet
central @ iso.ch
x.400 c=ch; a=4OOnet; p=iso; o=isocs; s=central
Printed in Switzerland
ii
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SIST EN ISO 11732:1999
IS0 11732: 1997(E)
Introduction
Methods using flow analysis are automatized 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).
One differentiates between flow injection analysis (FIA) [l], [2] and
continuous flow analysis (CFA) [3]. Both methods include the automatic
dosage of the sample into a flow system (manifold) in which the analytes in
the sample react with the reagent solutions on their way through the
manifold. The sample preparation may be integrated in the manifold. The
reaction product is analysed spectrometrically in a flow detector.
. . .
III
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SIST EN ISO 11732:1999
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SIST EN ISO 11732:1999
INTERNATIONAL STANDARD @ IS0 IS0 11732:1997(E)
Water quality - Determination of ammonium nitrogen by flow
analysis (CFA and FIA) and spectrometric detection
1 Determination of ammonium nitrogen by flow injection analysis (FIA) and
spectrometric detection
1.1 Scope
1 A.1 Field of application
This International Standard specifies a method 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,l to 10 mg/l
(in the undiluted sample). In particular cases, the range of application may be adapted by varying the operating
conditions.
1 A.2 interferences
Volatile amines will 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, erroneously high results may be
expected WI. In significant cases, prior to analysis an (online) distillation of the sample, adjusted to a pH of 5,8 may
be necessary.
Interferences may occur in exceptional cases when the sample does not reach a pH at least 12 after the addition of
the alkaline reagent, since then ammonium will not be converted quantitatively into ammonia. In particular, this may
occur with strongly acidic or buffered samples. In such cases the pH of the sample should be adjusted to 3 to 5 by
the addition of sodium hydroxide solution (1.4.1 or 1.4.2).
High concentrations of metal ions which may precipitate as hydroxides will give poorly reproducible results. The
addition of a suitable complexing agent, such as (ethylenedinitrilo)tetraacetic acid, disodium salt, to the alkaline
reaction solution (1.4.17) in a sufficiently large concentration will prevent interference by Cu, Zn, Fe, Ca, Mg and Al;
up to individual metal concentrations of 0,2 mg/l, a concentration of 30 g/l of ethylenedinitrilotetraacetic acid,
disodium salt, in solution RI (see 1.4.17) is adequate.
For samples containing particulate matter, see 1.6 (last paragraph).
Samples with a total salt concentration of > 10 g/l should be diluted prior to measurement.
1.2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. All standards are subject to revision, and parties to agreements based on this International
Standard are encouraged to investigate the possibility of applying the most recent editions of the standards
indicated below. Members of IEC and IS0 maintain registers of currently valid International Standards.
IS0 3696: 1987, Water for analytical and laboratory use - Specification and test methods.
IS0 5667-1 :1980, Water quality - Sampling - Part 1: Guidance on the design of sampling programmes.
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SIST EN ISO 11732:1999
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IS0 11732:1997(E)
IS0 5667.2:1991, W’ater quality - Sampling - Part 2: Guidance on sampling techniques.
IS0 5667-3:1994, Water quality - Sampling - Part 3: Guidance on the preservation and handling of samples.
1.3 Principle
The test sample containing ammonium is injected into a continuous carrier stream by means of an injection valve,
and is mixed with a continuous 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 colour; the colour change is monitored
continuously in a flow spectrophotometer. Additional information concerning this analytical technique is given in [4],
j51, PI, 171 and PI.
1.4 Reagents
Apart from the reagents listed in II .4.4 to 1.4.6, use only reagents of analytical grade quality for the determination of
nitrogen or, if not available, those of recognized analytical grade quality and water of grade 1 (in accordance with
IS0 3696), freshly prepared. The ammonium content of the blank shall be checked regularly (see 1.7.3).
1.4.1 Sodium hydroxide solution I, c(NaOH) = 5 mol/l.
1.4.2 Sodium hydroxide solution II, c(NaOH) = 0,Ol mol/l.
1.4.3 Ethylenedinitrilotetraacetic acid (EDTA), disodium salt, monohydrate, Na2C10H14N2Cso H20.
1.4.4 Bromcresol purple, C21 H16Br&S.
1.4.5 Bromthymol blue, C27H2sBr2CsS.
1.4.6 Cresol red, C21 H1805S
1.4.7 Ammonium chloride, NH&I, dried at 105 “C to constant weight.
1.4.8 Potassium chloride, KCI.
1.4.9 Boric acid, HaBOa.
1.4.10 Ethanol, CzHsOH, 95 % mass fraction.
1.4.11 Hydrochloric acid I, c(HCI) = 0,Ol mol/l.
1.4.12 Hydrochloric acid II, c(HCI) = 0,l mol/l.
1.4.13 Hydrochloric acid Ill, c(HCI) = 1,O mol/l.
1.4.14 Sulfuric acid, p(H2SO4) = 1,84 g/ml.
1.4.15 Mixed indicator.
In a mortar prepare a dry mixture consisting of 10 g of Bromcresol purple (1.4.4), 5 g of Bromthymol blue (1.4.5),
2,5 g of Cresol red (1.4.6) and 45 g of potassium chloride (1.4.8).
The given quantities can be reduced (e.g. by one-tenth), maintaining the ratio.
1.4.16 Carrier solution, C (see figure 1).
Use grade 1 water (IS0 3696), degassed by reduced pressure.
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SIST EN ISO 11732:1999
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1.4.17 Alkaline reaction solution, RI (see figure 1).
Dissolve in a graduated flask, nominal capacity 1 000 ml, 30 g of EDTA disodium salt (1.4.3) in approximately
800 ml of water, and add 12,4 g of boric acid (1.4.9).
Add dropwise to the suspension 100 ml of sodium hydroxide solution I (1.4.1), and make up to volume with water.
Degas the solution by filtering it through a membrane filter assembly (see 1.5.2).
The pH of the solution will be approximately 13. When stored in a polyethylene bottle at room temperature, it will be
stable for 1 month.
1.4.18 Indicator solution
In a graduated flask, nominal capacity 200 ml, dissolve 1 g of the mixed indicator (1.4.15) in a mixture of 10 ml of
sodium hydroxide solution II (1.4.2) and 10 ml of ethanol (1.4.10).
Add approximately 150 ml of water.
The solution should have a bright orange-red colour. If it has a blue colour, add hydrochloric acid
I I I dropwise
(1.4.13) until the colour changes.
Make up to volume with water.
Filter off any undissolved particles.
This solution can be stored without deterioration at room temperature for 3 months in a brown glass bottle.
1.4.19 Ammonia recipient solution, R2 (see figure 1)
Dilute 10 ml of the indicator solution (1.4.18) with approximately 480 ml of water.
Add dropwise sodium hydroxide solution II (1.4.2) until an absorbance value of 0,45 to 0,6 (pathlength 10 mm,
wavelength 590 nm) is obtained. Make up to a volume of 500 ml with water.
Degas and purify the solution using the membrane filter assembly (see 1.5.2), pour it into the reagent reservoir and
let it stand for at least 2 h.
Immediately before starting the measurement (1.7), check the absorbance again and adjust, if need be, to the
absorbance range specified above by adding sodium hydroxide solution II (1.4.2) or hydrochloric acid I, II or Ill
(1.4.11 to 1.4.13).
This solution can be stored without deterioration at room temperature for 2 weeks in a glass bottle.
1.4.20 Ammonium stock solution, ps(N) = 1 000 mg/l.
In a graduated flask, nominal capacity 1 000 ml, dissolve, 3,819 g of ammonium chloride (1.4.7) in approximately
900 ml water, acidify with sulfuric acid (1.4.14) to pH 2, and make up to volume with water.
This solution can be stored without deterioration in a refrigerator for at least 3 months.
1.4.21 Ammonium standard solution I, /Q(N) = 100 mg/l.
Pipette 10 ml of the ammonium stock solution (1.4.20) into a graduated flask, nominal capacity 100 ml, add
approximately 80 ml water, acidify with sulfuric acid (1.4.14) to pH 2, and make up to volume with water.
This solution can be stored without deterioration in a refrigerator for at least 1 week.
1.4.22 Ammonium standard solution II, p(N) = 10 mg/l.
Pipette 1 ml of the ammonium stock solution (1.4.20) or 10 ml of the ammonium standard solution I (1.4.21) into a
graduated flask, nominal capacity 100 ml, add approximately 80 ml water, acidify with sulfuric acid (1.4.14) to pH 2,
and make up to volume with water.
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This solution can be stored without deterioration in a refrigerator for at least 1 week.
1.4.23 Calibration solutions
Prepare the calibration solutions by diluting the ammonium standard solution I or II (1.4.21 or 1.4.22). At least five
calibration standards per working range are recommended. Proceed for the working range I or II respectively, as
follows:
a) Working range I [for mass concentrations ~B(N) = 1 mg/l to 10 mg/l]:
Pipette into a series of graduated flasks, nominal capacity 100 ml each, 1 ml, 3 ml, 5 ml, 7 ml and 9 ml respectively
of ammonium standard solution I (1.4.21), and make up to volume with water.
The mass concentrations of ammonium, expressed as nitrogen, in these calibration solutions are respectively
1 mg/l, 3 mg/l, 5 mg/l, 7 mg/l and 9 mg/l.
b) Working range II [for mass concentrations ~B(N) = 0,l mg/l to 1,O mg/l]:
Pipette into a series of graduated flasks, nominal capacity 100 ml each, 1 ml, 3 ml, 5 ml, 7 ml and 9 ml respectively
of the ammonium standard solution II (1.4.22), and make up to volume with water.
The mass concentrations of ammonium, expressed as nitrogen, in these calibration solutions are respectively
0,l mg/l, 0,3 mg/l, 0,5 mg/l, 0,7 mg/l and 0,9 mg/l.
All calibration solutions shall freshly be prepared before use.
1.5 Apparatus
1.5.1 Flow injection system
In general, the flow injection system consists of the following components (see figure 1):
reagent reservoirs;
- low pulsation pump;
- suitable pump tubes, if required;
- injection valve with a suitable injection volume;
- diffusion cell with hydrophobic semipermeable membrane [e.g. made from polytetrafluoroethylene (PTFE)].
NOTE - Example of a typical membrane:
- thickness: 150 pm to 200 pm;
-
pore size: 0,5 pm to 2,0 pm;
- porosity: 75 %.
- transport tubes and reaction coils, internal diameter 0,5 mm to 0,8 mm, tube connections and T-connections of
inert plastic and with minimum dead volumes;
- spectrophotometric detector with flow cell, normal path length 10 mm to 50 mm, wavelength range 580 nm to
600 nm;
- recording unit (e.g. strip chart recorder, integrator or printer/plotter). In general peak height signals are
evaluated;
autosampler, if required.
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SIST EN ISO 11732:1999
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2
3
4
C 23
4
Waste
R OB
1
-----------
R zo Waste
2
-
Typical injection time: 20 s to 25 s
Typical residence time: approx. 45 s
Key
C Carrier solution 2 Sample injection valve
400 ~1 [working range I: m(N) = 1 mg/l to 10 mg/l]
RI Alkaline reagent solution
40 yl [working range II: m(N) = 0,l mg/l to 1,O mg/l]
R2 Ammonia recipient solution
3 Reaction coil
D Detector for 580 nm to 600 nm
length: 30 cm/0 int. 0,5 mm to 0,8 mm
I Pump (ml/min)
4
Gas diffusion cell
5 PTFE membrane
Figure 1 - Example of a flow injection system for ammonium nitrogen concentrations for 0,l mg/l to 10 mg/l
1 S.2 Additional apparatus
- graduated flasks, nominal capacity 100 ml, 200 ml and 1 000 ml;
- graduated pipettes, nominal capacity 1 ml to 10 ml;
- membrane filter assembly with membrane filters, pore size 0,45 pm.
1.6 Sampling
Containers of glass, polyalkylenes and polytetrafluoroethylene (PTFE) are suitable for sample collection. All
containers coming in contact with the sample shall be cleaned thoroughly with hydrochloric acid I, II or Ill (1.4.11 to
1.4.13) and shall be rinsed several times with water.
Analyze the samples immediately after collection. Alternatively, add sulfuric acid (1.4.14) to adjust to a pH of
approximately 2, store at 2 “C to 5 “C in the dark, and analyze within the next 24 h.
In exceptional cases, the sample may be stored up to 2 weeks provided it has been membrane-filtered after
acidification. The applicability of this preservation procedure shall be checked for each individual case.
If there is a risk of clogging the injection system transport tubes, the samples shall be filtered before analysis.
1.7 Procedure
1.7.1 Preparation of the measurement
Prior to measurement, continuously run the reagent solutions C, R1 and R2 for approximately 10 min through the
flow injection system, record and zero the baseline.
The system is ready when the baseline no longer shows any drift. A satisfactory signal-to-noise ratio should be
obtained. Check the reagent blank and the operation of the membrane in accordance with 1.7.3. Calibrate the
system as described in 1.7.4.
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1.7.2 Quality requirements for the measuring system
In the measuring system being calibrated for working range I, a calibration solution (1.4.23) with mass concentration
0,5 mg/l shall give an absorbance of at least 0,040 per 10 mm pathlength.
NOTE - If the spectrophotometric detector does not give any absorbance readings, the absorbance may then be determined
by comparing with an external absorbance-measuring spectrometer.
1.7.3 Checking reagent blank
Wait for the baseline to stabilize.
Instead of the alkaline reagent solution RI, run water through the system until a stable signal is obtained. Record
the change in absorbance.
If the absorbance changes by more than 0,l per 10 mm pathlength, either the water being used or the alkaline
or the semipermeable membrane may be faulty.
reagent solution may be contaminated with ammonium,
Appropriate measures shall then be taken to remedy the fault.
Run the reagent solutions again.
1.7.4 Calibration
Select working range I or II and prepare the calibration solutions for the selected working range (1.4.23). Perform a
separate calibration for each working range.
For working range I, use an injection volume of 40 ~1, for working range II a volume of 400 ~1.
Prior to the calibration, zero the system, in accordance with the manufacturer’s instructions, if necessary.
Calibrate by alternately injecting calibration solutions and blank
...
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