SIST EN ISO 18724:2025

SLOVENSKI STANDARD
01-november-2025
Kakovost vode - Določanje kroma (VI), raztopljenega v vodi - Fotometrijska
metoda (ISO 18724:2025)
Water quality - Determination of dissolved chromium(VI) in water - Photometric method
(ISO 18724:2025)
Wasserbeschaffenheit - Bestimmung des gelösten Chrom(VI) in Wasser -
Photometrisches Verfahren (ISO 18724:2025)
Qualité de l'eau - Détermination du chrome dissous(VI) dans l'eau - Méthode
photométrique (ISO 18724:2025)
Ta slovenski standard je istoveten z: EN ISO 18724:2025
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.

EN ISO 18724
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2025
EUROPÄISCHE NORM
ICS 13.060.50
English Version
Water quality - Determination of dissolved chromium(VI)
in water - Photometric method (ISO 18724:2025)
Qualité de l'eau - Détermination du chrome dissous(VI) Wasserbeschaffenheit - Bestimmung des gelösten
dans l'eau - Méthode photométrique (ISO 18724:2025) Chrom(VI) in Wasser - Photometrisches Verfahren (ISO
18724:2025)
This European Standard was approved by CEN on 14 September 2025.

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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 18724:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 18724:2025) 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 April 2026, and conflicting national standards shall be
withdrawn at the latest by April 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 18724:2025 has been approved by CEN as EN ISO 18724:2025 without any modification.

International
Standard
ISO 18724
First edition
Water quality — Determination of
2025-10
dissolved chromium(VI) in water —
Photometric method
Qualité de l'eau — Détermination du chrome dissous(VI) dans
l'eau — Méthode photométrique
Reference number
ISO 18724:2025(en) © ISO 2025
ISO 18724:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 18724:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Interferences . 1
4.1 General .1
4.2 Sampling, preservation and storage .2
4.3 Interferences in photometry .2
5 Principle . 2
6 Reagents . 3
7 Apparatus . 6
8 Sampling, sample pretreatment and sample storage . 6
8.1 Sampling .6
8.2 Samples with reducing or oxidizing substances .6
8.3 Consideration of the self-absorption of coloured samples .7
8.4 Sample storage .7
9 Procedure . 7
9.1 General .7
9.2 Required concentrations of reagents in the reaction vessel .7
9.3 Required concentrations of reagents in the reaction vessel for measuring the intrinsic
absorption .8
9.4 Measurement .8
9.5 Calibration .8
9.6 Measurement of chromium(VI).8
9.7 Validity check of the calibration function .8
9.8 Calculation considering the ordinate intercept .9
9.9 Calculation with zero adjustment of the photometer .9
10 Expression of results . 9
11 Test report . 10
Annex A (normative) Manual static technique .11
Annex B (normative) Automated static techniques .13
Annex C (normative) Automated dynamic techniques .15
Annex D (normative) Calculations for adjusting reagent concentrations, volumes and flows .22
Annex E (informative) Performance data .25
Bibliography .28

iii
ISO 18724:2025(en)
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.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s).
...