EN ISO 11969:1996

SLOVENSKI STANDARD
01-januar-1998
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Water quality - Determination of arsenic - Atomic absorption spectrometric method
(hydride technique) (ISO 11969:1996)
Wasserbeschaffenheit - Bestimmung von Arsen - Atomabsorptionsspektrometrie
(Hydridverfahren) (ISO 11969:1996)
Qualité de l'eau - Dosage de l'arsenic - Méthode par spectrométrie d'absorption
atomique (technique hydrure) (ISO 11969:1996)
Ta slovenski standard je istoveten z: EN ISO 11969:1996
ICS:
13.060.50 3UHLVNDYDYRGHQDNHPLþQH Examination of water for
VQRYL chemical substances
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL IS0
STANDARD
First edition
1996-07-15
Water quality - Determination of
arsenic - Atomic absorption
spectrometric method (hydride technique)
Qua/it6 de I ’eau - Dosage de / ‘arsenic - M&hode par spectromktrie
d ‘absorp tion a tomique (technique h ydrure)
Reference number
IS0 11969:1996(E)
IS0 11969:1996(E)
Foreword
IS0 (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 11969 was prepared by Technical Committee
lSO/TC 147, l,&ter quality, Subcommittee SC 2, Physical, chemical,
biochemical methods.
Annexes A and B of this International Standard are for information only.
0 IS0 1996
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.
lnternationa I Organization for Standardization
Case Postal tzerland
e 56 l CH-1211 Geneve 20 l Swi
Printed in Switzerland
IS0 11969:1996(E)
INTERNATIONAL STANDARD 0 IS0
- Determination of arsenic - Atomic
spectrometric meth
(hydride technique)
WARNING - Arsenic and arsenic compounds are toxic and are recognized as human carcinogens.
Avoid any exposure by inhalation. Personal protection must be used in all cases where exposure
to arsenic or arsenic compounds is possible.
4 Scope 3 Principle
The method is based on the atomic absorption
This International Standard specifies a method for the
measurement of arsenic generated by the thermal
determination of arsenic including organically bound
arsenic in drinking waters, ground waters and surface decomposition of arsenic(l I I) hydride.
waters, in a concentration range from 1 pg/l to
Under the conditions of this method, only As(lIl) is
10 l-m
quantitatively converted to the hydride. To avoid er-
rors in determination, other oxidation states need to
Higher concentrations can be determined by using a
be converted to As(lll) prior to the determination.
suitable dilution of the water sample.
As(lIl) is reduced to gaseous arsenic(l II) hydride
(ASH,) by reaction with sodium tetrahydroborate in a
hydrochloric acid medium.
2 Normative references
The absorbance is determined at a wavelength of
The following standards contain provisions which,
193,7 nm.
through reference in this text, constitute provisions
of this International Standard. At the time of publi-
cation, the editions indicated were valid. All standards
4 Reagents
are subject to revision, and parties to agreements
based on this International Standard are encouraged
During the analysis, use only reagents of recognized
to investigate the possibility of applying the most re-
analytical grade.
cent editions of the standards indicated below.
Members of IEC and IS0 maintain registers of cur-
The arsenic content of the water and the reagents
rently valid International Standards.
shall be negligible, compared with the lowest con-
centration to be determined.
IS0 5667-l : 1980, Water quality - Sampling -
Part 7: Guidance on the design of sampling pro-
grammes. 4.1 Sulfuric acid (H2S04), p = I,84 g/ml.
IS0 5667-2:1991, Water quality - Sampling -
4.2 Hydrochloric acid (HCI), p = 1 ,I 5 g/ml.
Part 2: Guidance on sampling techniques.
IS0 5667-3: 1994, Water quality - Sampling -
4.3 Hydrogen peroxide (H,O,), w = 30 % (mjm).
Part 3: Guidance on the preservation and handling of
samples.
4.4 Sodium hydroxide (NaOH).
IS0 11969:1996(E)
Prepare the solution on the day of use.
4.5 Sodium tetrahydroborate solution.
Dissolve 1 g of sodium hydroxide (4.4) in about
5 Apparatus
20 ml of water. Add 3 g of sodium tetrahydroborate
(NaBH,). Dilute to 100 ml with water.
Usual laboratory apparatus and
Prepare the solution on the day of use.
5.1 Atomic absorption spectrometer, fitted with
NOTE 1 For flow-through systems, it is recommended to
a hydride system, and a suitable radiation source for
follow the instructions of the manufacturer. A solution con-
determination of arsenic, for example
the
taining 0,5 % of sodium tetrahydroborate and 0,5 % of
electrodeless discharge lamp or a hollow cathode
sodium hydroxide is suitable. This solution is stable for at
lamp with a background correction facility, if necess-
least one week.
ary.
4.6 Potassium iodide-ascorbic acid solution.
5.2 Gas supply, with argon or nitrogen.
Dissolve 3 g of potassium iodide (KI) and 5 g of
L(+)-ascorbic acid (C,H,O,) in 100 ml of water.
5.3 Glassware, to be cleaned immediately before
use with warm, dilute nitric acid [I 0 % (V/V)] and
Prepare the solution on the day of use.
rinsed with water.
NOTE 2 It is unnecessary to use ascorbic acid if a 20 %
solution of potassium iodide is used.
6 Sampling
4.7 Arsenic stock solution, corresponding to
Take samples according to IS0 5667-l and
1 000 mg of As per Iitre.
IS0 5667-2.
Place 1,320 g of arsenic(lII) oxide (As,O,), in a
Collect samples in polyethylene or borosilicate glass
volumetric flask of nominal capacity 1 000 ml. Add
containers which have been previously cleaned with
2 g of sodium hydroxide (4.4) and dissolve in a small
nitric acid [e.g. 10 % (V/V)] and then rinsed with
quantity of water. Dilute to volume with water.
water.
This solution is stable for at least 1 year.
On site, add 20 ml of hydrochloric acid (4.2) to each
1 000 ml of the water sample.
Arsenic stock solutions are commercially available.
If the stock solution contains As(V), the standard sol-
If the pH of the sample is still greater than 2, add
utions shall be treated in the same way as the sample
more hydrochloric acid until the pH is 2 or less.
for the reduction step (8.3.2).
For sample conservation, see IS0 5667-3.
4.8 Arsenic standard solution 1, corresponding to
10 mg of As per litre.
7 Interferences
Pipette 10 ml of arsenic stock solution (4.7) into a
Most organic materials interfere with the arsenic de-
volumetric flask of nominal capacity 1 000 ml. Add
termination. They shall be removed prior to the
20 ml of hydrochloric acid (4.2) and dilute to volume
analysis by the digestion procedure described in
with water.
8.3.1. Samples forming foams when tetrahydroborate
is added shall be pretreated (e.g. with an anti-foaming
The solution is stable for about 1 month.
agent or by complete digestion). When an anti-
If a stock solution of arsenic(V) is used
...