ISO/TS 19620:2018

TECHNICAL ISO/TS
SPECIFICATION 19620
First edition
2018-01
Water quality — Determination of
arsenic(III) and arsenic(V) species
— Method using high performance
liquid chromatography (HPLC) with
detection by inductively coupled
plasma mass spectrometry (ICP-
MS) or hydride generation atomic
fluorescence spectrometry (HG-AFS)
Qualité de l'eau — Détermination des formes chimiques (III) et (V)
d'arsenic — Méthode par chromatographie en phase liquide à haute
performance (HPLC) avec détection par spectrométrie de masse
par torche à plasma (ICP-MS) ou génération d'hydrure fluorescence
atomique (HG-AFS)
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principle . 3
5 Interferences . 3
6 Apparatus . 3
7 Reagents and standards . 4
8 Sampling, preservation and storage of samples . 6
9 Procedure. 6
9.1 HPLC instrument optimization . 6
9.2 Calibration . 7
9.3 Sample measurement . 7
10 Expression of results . 7
11 Test report . 8
Annex A (normative) Detection using inductively coupled plasma mass spectrometry (ICP-MS) .9
Annex B (normative) Detection using hydride generation atomic fluorescence (HG-AFS) .20
Annex C (informative) Determination of organic arsenic species .27
Annex D (informative) Storage and preservation of arsenic species in water samples .29
Bibliography .40
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
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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 documents 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).
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URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2,
Physical, chemical and biochemical methods.
iv © ISO 2018 – All rights reserved

Introduction
In the environment, metals and metalloids are found in the form of various chemical species. Chemical
speciation makes it possible to identify and quantify these different species. For the same metal or
metalloid, given that the toxicity of each compound may vary significantly, it can be useful to quantify
each of the species present in a given sample. For arsenic, the toxicity of the various species varies
considerably; inorganic species are recognized as being more toxic than organic species and, for
example, the toxicity of As(III) is greater than that of As(V). This method is primarily applicable to the
determination of arsenite (As(III)) and arsenate (As(V)) as these are the main species of interest and
are the predominant species found in potable water samples from the underlying geological strata in
many parts of the world. Arsenic speciation measurements are important to establish and select the
best water treatment technology for arsenic removal from raw waters containing significant levels of
arsenic.
TECHNICAL SPECIFICATION ISO/TS 19620:2018(E)
Water quality — Determination of arsenic(III) and
arsenic(V) species — Method using high performance liquid
chromatography (HPLC) with detection by inductively
coupled plasma mass spectrometry (ICP-MS) or hydride
generation atomic fluorescence spectrometry (HG-AFS)
WARNING — Persons using this document should be familiar with normal laboratory practice.
This document is not intended to cover any safety problems associated with its use, if applicable.
It is the responsibility of the user to establish appropriate safety and health practices.
IMPORTANT — It is absolutely essential that tests conducted in accordance with this document
be carried out by suitably qualified staff.
1 Scope
This document specifies a method primarily developed for the determination of inorganic arsenic
species (arsenite (As(III)) and arsenate (As(V)) dissolved in a sample after a preservation process
in waters with a low total organic carbon content such as potable water, tap water, surface waters,
ground waters and rain waters. Information is provided on the determination of potentially relevant
organo-arsenic species such as methylarsonic acid (MMA) and dimethylarsinic acid (DMA) which may
be encountered at very low levels in natural surface waters.
The linear working dynamic range depends on the operating conditions and the method of detection
used; under standard conditions, it typically ranges from 0,5 µg/l to 50 µg/l for each species. Samples
containing arsenic at concentrations higher than the linear dynamic range can be analysed after
suitable dilution.
This method is based on high performance liquid chromatography separation of arsenic species with
either inductively coupled mass spectrometry (ICP-MS) or hydride generation atomic fluorescence
spectrometry (HG-AFS) as a method of detection.
The sensitivity of this method depends on the method of detection and the instrumental operating
conditions selected. The limit of quantification (LOQ) of the method also depends on the operating
conditions of the analytical system used and the extent of the calibration range used. LOQ examples for
As(III) and As(V) are provided; LOQs are generally less than 1 µg/l.
This document does not apply to arsenobetaine and other organic arsenic species which are not present
in natural water samples.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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, Water for analytical laboratory use — Specification and test methods
ISO 5667-1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes and
sampling techniques
ISO 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples
ISO 17294-1, Water quality — Application of inductively coupled plasma mass spectrometry (ICP-MS) —
Part 1: General guidelines
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org./obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1
analyte
substance to be determined
[SOURCE: ISO/TS 28581:2012, 3.1]
3.2
blank calibration solution
solution prepared in the same way as the calibration solution but leaving out the analyte
[SOURCE: ISO 17294-1:2004, 3.3]
3.3
calibration solution
solution used to calibrate the instrument, prepared from (a) stock solution(s) or from a certified
standard
[SOURCE: ISO 17294-1:2004, 3.4]
3.4
stock solution
solution with accurately known analyte concentration(s), prepared from suitably pure chemicals
[SOURCE: ISO 17294-1:2004, 3.30]
3.5
determination
entire process from preparing the test sample solution up to and including measurement and calculation
of the final result
[SOURCE: ISO 17294-1:2004, 3.6]
3.6
limit of quantification
LOQ
lowest concentration of an analyte that can be determined with a specified degree of accuracy and
precision
3.7
limit of detection
LOD
lowest concentration of an analyte that can be detected with a specified degree of accuracy and
precision
2 © ISO 2018 – All rights reserved

4 Principle
The different arsenic species are separated using a specific column in a high performance liquid
chromatograph (HPLC). The separation of arsenic species in natural water is typically achieved using
strong anion exchange ion chromatography. The species can be separated using isocratic conditions
however faster more efficient separations can be achieved using gradient elution.
This method permits the use of ICP-MS (see Annex A) or HG-AFS (see Annex B) for individual detection
of the various arsenic species.
Annex C provides information on the determination of organic arsenic species.
Annex D provides information on the stability of arsenic species using different storage and
preservations.
5 Interferences
Retention time shift may occur for some water samples, especially when they are enriched with
significant levels of various water matrix ions. These ions compete with the active sites on the column.
Sample spikes using each of the arsenic species should therefore be used to confirm species identity if
a retention time shift is observed. The sample may also be diluted to overcome this effect or a smaller
injection volume may be used with an inferior LOQ. The co-elution of organic arseni
...