SIST EN ISO 20595:2023
(Main)Water quality - Determination of selected highly volatile organic compounds in water - Method using gas chromatography and mass spectrometry by static headspace technique (HS-GC-MS) (ISO 20595:2018)
Water quality - Determination of selected highly volatile organic compounds in water - Method using gas chromatography and mass spectrometry by static headspace technique (HS-GC-MS) (ISO 20595:2018)
ISO 20595:2018 specifies a method for the determination of selected volatile organic compounds in water (see Table 1). This comprises among others volatile halogenated hydrocarbons as well as gasoline components (BTXE, TAME, MTBE and ETBE).
The method is applicable to the determination of volatile organic compounds (see Table 1) in drinking water, groundwater, surface water and treated waste water in mass concentrations >0,1 µg/l. The lower application range depends on the individual compound, the amount of the blank value and the matrix.
Wasserbeschaffenheit - Bestimmung ausgewählter leichtflüchtiger organischer Verbindungen in Wasser - Verfahren mittels Gaschromatographie und Massenspektrometrie nach statischer Headspacetechnik (HS-GC-MS) (ISO 20595:2018)
Dieses Dokument legt ein Verfahren für die Bestimmung von ausgewählten leichtflüchtigen organischen Verbindungen in Wasser (siehe Tabelle 1) fest. Hierbei handelt es sich z. B. um leichtflüchtige Halogenkohlenwasserstoffe (LHKW) sowie um Benzininhaltstoffe (BTXE, TAME, MTBE und ETBE).
Das Verfahren ist anwendbar auf die Bestimmung von leichtflüchtigen organischen Verbindungen (siehe Tabelle 1) in Trink , Grund , Oberflächenwasser und Abwasser in Massenkonzentrationen >0,1 µg/l. Der untere Anwendungsbereich ist von der individuellen Verbindung, der Höhe des Blindwerts und der Matrix abhängig.
Die Anwendbarkeit des Verfahrens auf weitere, in Tabelle 1 nicht genannte, leichtflüchtige organische Verbindungen ist nicht ausgeschlossen, sie muss jedoch im Einzelfall geprüft werden.
[Tabelle 1]
Qualité de l'eau - Dosage de composés organiques hautement volatils sélectionnés dans l'eau - Méthode par chromatographie en phase gazeuse par la technique de l'espace de tête statique et spectrométrie de masse (HS-GC-MS) (ISO 20595:2018)
ISO 20595:2018 spécifie une méthode pour le dosage de composés organiques volatils sélectionnés dans l'eau (voir Tableau 1). Ceux-ci comprennent, entre autres, des hydrocarbures halogénés volatils ainsi que des constituants de l'essence (BTXE, TAME, MTBE et ETBE).
La méthode est applicable au dosage de composés organiques volatils (voir Tableau 1) présents dans l'eau potable, les eaux souterraines, les eaux de surface et les eaux résiduaires traitées à des concentrations massiques > 0,1 µg/l. La limite inférieure du domaine d'application dépend du composé particulier, de l'importance de la valeur du blanc et de la matrice.
Kakovost vode - Določevanje izbranih lahko hlapnih organskih spojin v vodi - Metoda s plinsko kromatografijo s statično "headspace" tehniko in z masno spektrometrijo (HS-GC-MS) (ISO 20595:2018)
Standard ISO 20595:2018 določa metodo za določanje izbranih hlapnih organskih spojin v vodi (glej preglednico 1). To med drugim vključuje hlapne halogenirane ogljikovodike ter sestavine bencina (BTXE, TAME, MTBE in ETBE).
Metoda se uporablja za določanje hlapnih organskih spojin (glej preglednico 1) v pitni vodi, podtalnici, površinski vodi in očiščeni odpadni vodi v masnih koncentracijah >0,1 µg/l. Spodnje področje uporabe je odvisno od posamezne spojine, vrednosti slepega vzorca in matrice.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-april-2023
Kakovost vode - Določevanje izbranih lahko hlapnih organskih spojin v vodi -
Metoda s plinsko kromatografijo s statično "headspace" tehniko in z masno
spektrometrijo (HS-GC-MS) (ISO 20595:2018)
Water quality - Determination of selected highly volatile organic compounds in water -
Method using gas chromatography and mass spectrometry by static headspace
technique (HS-GC-MS) (ISO 20595:2018)
Wasserbeschaffenheit - Bestimmung ausgewählter leichtflüchtiger organischer
Verbindungen in Wasser - Verfahren mittels Gaschromatographie und
Massenspektrometrie nach statischer Headspacetechnik (HS-GC-MS) (ISO 20595:2018)
Qualité de l'eau - Dosage de composés organiques hautement volatils sélectionnés dans
l'eau - Méthode par chromatographie en phase gazeuse par la technique de l'espace de
tête statique et spectrométrie de masse (HS-GC-MS) (ISO 20595:2018)
Ta slovenski standard je istoveten z: EN ISO 20595:2022
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 20595
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2022
EUROPÄISCHE NORM
ICS 13.060.50
English Version
Water quality - Determination of selected highly volatile
organic compounds in water - Method using gas
chromatography and mass spectrometry by static
headspace technique (HS-GC-MS) (ISO 20595:2018)
Qualité de l'eau - Dosage de composés organiques Wasserbeschaffenheit - Bestimmung ausgewählter
hautement volatils sélectionnés dans l'eau - Méthode leichtflüchtiger organischer Verbindungen in Wasser -
par chromatographie en phase gazeuse par la Verfahren mittels Gaschromatographie und
technique de l'espace de tête statique et spectrométrie Massenspektrometrie nach statischer
de masse (HS-GC-MS) (ISO 20595:2018) Headspacetechnik (HS-GC-MS) (ISO 20595:2018)
This European Standard was approved by CEN on 19 September 2022.
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
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 20595:2022 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
European foreword
The text of ISO 20595:2018 has been prepared by Technical Committee ISO/TC 147 "Water quality” of
the International Organization for Standardization (ISO) and has been taken over as EN ISO 20595:2022
by 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 March 2023, and conflicting national standards shall
be withdrawn at the latest by March 2023.
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.
Any feedback and questions on this document should be directed to the users’ national standards body.
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 20595:2018 has been approved by CEN as EN ISO 20595:2022 without any modification.
INTERNATIONAL ISO
STANDARD 20595
First edition
2018-01
Water quality — Determination
of selected highly volatile organic
compounds in water — Method
using gas chromatography and mass
spectrometry by static headspace
technique (HS-GC-MS)
Qualité de l'eau — Dosage de composés organiques hautement
volatils sélectionnés dans l'eau — Méthode par chromatographie
en phase gazeuse par la technique de l'espace de tête statique et
spectrométrie de masse (HS-GC-MS)
Reference number
ISO 20595:2018(E)
©
ISO 2018
ISO 20595:2018(E)
© ISO 2018
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
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Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
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Published in Switzerland
ii © ISO 2018 – All rights reserved
ISO 20595:2018(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 3
3 Terms and definitions . 3
4 Principle . 3
5 Interferences . 4
5.1 General . 4
5.2 Interferences in the laboratory . 4
5.3 Interferences by the matrix. 4
5.4 Interferences in the headspace . 4
5.5 Interferences during gas chromatography and mass spectrometry. 4
6 Reagents . 4
7 Apparatus . 6
8 Sampling . 6
9 Procedure. 7
9.1 Sample preparation . 7
9.2 GC-MS operating conditions . 7
9.3 Control measures . 7
9.3.1 Blank value control . 7
9.3.2 Control over the total procedure . 7
9.4 Identification of individual compounds . 8
9.4.1 General. 8
9.4.2 Identification of individual compounds with mass spectrometric detector . 8
10 Calibration .10
10.1 General .10
10.2 Calibration with internal standard .11
11 Evaluation .12
12 Expression of results .12
13 Test report .12
Annex A (informative) Example of GC column, headspace vial and septum .13
Annex B (informative) Examples of internal standards .14
Annex C (informative) Example of headspace and gas chromatographic conditions .16
Annex D (informative) Performance data .17
Bibliography .24
ISO 20595:2018(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.
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).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
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
ISO 20595:2018(E)
Introduction
Various methods are available for the determination of highly volatile organic compounds in water.
This document specifies a gas chromatographic method with mass spectrometric detection (GC-MS)
for the determination of volatile organic compounds using the static headspace technique (HS).
INTERNATIONAL STANDARD ISO 20595:2018(E)
Water quality — Determination of selected highly
volatile organic compounds in water — Method using
gas chromatography and mass spectrometry by static
headspace technique (HS-GC-MS)
WARNING — Persons using this document should be familiar with normal laboratory practice.
This document 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.
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 for the determination of selected volatile organic compounds in
water (see Table 1). This comprises among others volatile halogenated hydrocarbons as well as gasoline
components (BTXE, TAME, MTBE and ETBE).
The method is applicable to the determination of volatile organic compounds (see Table 1) in drinking
water, groundwater, surface water and treated waste water in mass concentrations >0,1 µg/l. The lower
application range depends on the individual compound, the amount of the blank value and the matrix.
The applicability of the method to further volatile organic compounds not indicated in Table 1 is not
excluded, but this is checked in individual cases.
Table 1 — Volatile organic compounds determinable by this method
a b
Name (other name) Molecular formula CAS-RN EC-Number Molar mass
g/mol
c
allyl chloride (3-chloropropene) C H Cl 107-05-1 203-457-6 76,53
3 5
benzene C H 71-43-2 200-753-7 78,11
6 6
biphenyl C H 92-52-4 202-163-5 154,21
12 10
bromodichloromethane CHBrCl 75-27-4 200-856-7 163,83
chlorobenzene C H Cl 108-90-7 203-628-5 112,56
6 5
2-chloro-1,3-butadiene (chloroprene) C H Cl 126-99-8 204-818-0 88,54
4 5
2-chlorotoluene C H Cl 95-49-8 202-424-3 126,58
7 7
3-chlorotoluene C H Cl 108-41-8 203-580-5 126,58
7 7
4-chlorotoluene C H Cl 106-43-4 203-397-0 126,58
7 7
dibromochloromethane CHBr Cl 124-48-1 204-704-0 208,28
1,2-dibromoethane C H Br 106-93-4 203-444-5 187,86
2 4 2
1,2-dichlorobenzene C H Cl 95-50-1 202-425-9 147,00
6 4 2
1,3-dichlorobenzene C H Cl 541-73-1 208-792-1 147,00
6 4 2
a
CAS-RN: Chemical Abstracts Service Registry Number.
b
EC-Number: European Inventory of Existing Commercial Substances (EINECS) or European List of Notified Chemical
Substances (ELINCS).
c
Compounds do not have long-term stability.
d
Compounds can coelute.
e
Source: Hazardous Substance Data Base University Hamburg (Germany).
ISO 20595:2018(E)
Table 1 (continued)
a b
Name (other name) Molecular formula CAS-RN EC-Number Molar mass
g/mol
1,4-dichlorobenzene C H Cl 106-46-7 203-400-5 147,00
6 4 2
dichlorodiisopropyl ether C H Cl O 108-60-1 203-598-3 171,06
6 12 2
1,1-dichloroethane C H Cl 75-34-3 200-863-5 98,96
2 4 2
1,2-dichloroethane C H Cl 107-06-2 203-458-1 98,96
2 4 2
1,1-dichloroethene C H Cl 75-35-4 200-864-0 96,94
2 2 2
cis-1,2-dichloroethene C H Cl 156-59-2 205-859-7 96,94
2 2 2
trans-1,2-dichloroethene C H Cl 156-60-5 205-860-2 96,94
2 2 2
dichloromethane CH Cl 75-09-2 200-838-9 84,93
2 2
1,2-dichloropropane C H Cl 78-87-5 201-152-2 112,99
3 6 2
cis-1,3-dichloropropene C H Cl 10061-01-5 233-195-8 110,97
3 4 2
e
trans-1,3-dichloropropene C H Cl 10061-02-6 602-030-00-5 110,97
3 4 2
2,3-dichloropropene C H Cl 78-88-6 201-153-8 110,97
3 4 2
1,1-dimethylpropyl-methyl ether,
C H O 994-05-8 213-611-4 102,17
6 14
tert-amyl methyl ether (TAME)
ethyl benzene C H 100-41-4 202-849-4 106,17
8 10
ethyl tert-butyl ether (ETBE) C H O 637-92-3 211-309-7 102,17
6 14
hexachlorobutadiene C Cl 87-68-3 201-765-5 260,76
4 6
hexachloroethane C Cl 67-72-1 200-666-4 236,74
2 6
isopropylbenzene (cumene) C H 98-82-8 202-704-5 120,19
9 12
methyl tert-butyl ether (MTBE) C H O 1634-04-4 216-653-1 88,15
5 12
naphthalene C H 91-20-3 202-049-5 128,17
10 8
n-propylbenzene C H 103-65-1 203-132-9 120,19
9 12
1,1,1,2-tetrachloroethane C H Cl 630-20-6 211-135-1 167,85
2 2 4
tetrachloroethene C Cl 127-18-4 204-825-9 165,84
2 4
tetrachloromethane
CCl 56-23-5 200-262-8 153,82
(carbon tetrachloride)
toluene C H 108-88-3 203-625-9 92,14
7 8
tribromomethane (bromoform) CHBr 75-25-2 200-854-6 252,73
1,2,3-trichlorobenzene C H Cl 87-61-6 201-757-1 181,45
6 3 3
1,2,4-trichlorobenzene C H Cl 120-82-1 204-428-0 181,45
6 3 3
1,3,5-trichlorobenzene C H Cl 108-70-3 203-608-6 181,45
6 3 3
1,1,1-trichloroethane C H Cl 71-55-6 200-756-3 133,40
2 3 3
1,1,2-trichloroethane C H Cl 79-00-5 201-166-9 133,40
2 3 3
trichloroethene C HCl 79-01-6 201-167-4 131,39
2 3
trichloromethane (chloroform) CHCl 67-66-3 200-663-8 119,38
1,1,2-trichlorotrifluoroethane C Cl F 76-13-1 200-936-1 187,38
2 3 3
1,2,4-trimethylbenzene C H 95-63-6 202-436-9 120,19
9 12
(pseudocumene)
a
CAS-RN: Chemical Abstracts Service Registry Number.
b
EC-Number: European Inventory of Existing Commercial Substances (EINECS) or European List of Notified Chemical
Substances (ELINCS).
c
Compounds do not have long-term stability.
d
Compounds can coelute.
e
Source: Hazardous Substance Data Base University Hamburg (Germany).
2 © ISO 2018 – All rights reserved
ISO 20595:2018(E)
Table 1 (continued)
a b
Name (other name) Molecular formula CAS-RN EC-Number Molar mass
g/mol
1,3,5-trimethylbenzene (mesitylene) C H 108-67-8 203-604-4 120,19
9 12
vinyl benzene (styrene) C H 100-42-5 202-851-5 104,15
8 8
c
vinyl chloride (chloroethene) C H Cl 75-01-4 200-831-0 62,49
2 3
o-xylene C H 95-47-6 202-422-2 106,17
8 10
d
m-xylene C H 108-38-3 203-576-3 106,17
8 10
d
p-xylene C H 106-42-3 203-396-5 106,17
8 10
a
CAS-RN: Chemical Abstracts Service Registry Number.
b
EC-Number: European Inventory of Existing Commercial Substances (EINECS) or European List of Notified Chemical
Substances (ELINCS).
c
Compounds do not have long-term stability.
d
Compounds can coelute.
e
Source: Hazardous Substance Data Base University Hamburg (Germany).
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 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples
ISO 5667-4, Water quality — Sampling — Part 4: Guidance on sampling from lakes, natural and man-made
ISO 5667-5, Water quality — Sampling — Part 5: Guidance on sampling of drinking water from treatment
works and piped distribution systems
ISO 5667-6, Water quality — Sampling — Part 6: Guidance on sampling of rivers and streams
ISO 5667-10, Water quality — Sampling — Part 10: Guidance on sampling of waste waters
ISO 5667-11, Water quality — Sampling — Part 11: Guidance on sampling of groundwaters
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
4 Principle
An exact volume of an unfiltered water sample is sealed gastight in a headspace vial and heated. After
an equilibrium has become established between the volatile organic compounds dissolved in the water
and those located in the gas phase above the water level, an exact gas volume is taken from the gas
phase and determined by gas chromatography with mass spectrometric detection.
ISO 20595:2018(E)
5 Interferences
5.1 General
If a sample consists of several liquid phases, another method shall be applied.
5.2 Interferences in the laboratory
Some of the volatile organic compounds listed in Table 1 are frequently used as solvents in laboratories.
Solvent vapours in the laboratory air can lead to overestimates during the analysis. Regular blank value
examinations are therefore indispensable (see 9.3.1).
5.3 Interferences by the matrix
Matrix effects that lead to different recoveries and different response factors in samples in comparison
to calibration standards can be reduced by adding specific amounts of salt. An increase in the sensitivity
can also be attained by adding salt. The use of sodium sulfate or sodium chloride has proven effective.
However, interferences can occur depending on the salt used.
5.4 Interferences in the headspace
Some compounds can decompose while the equilibrium forms at e.g. 80 °C. For example,
1,1,2,2-tetrachloroethane decomposes to trichloroethene. If 1,1,2,2-tetrachloroethane is present in the
sample, overestimates of trichloroethene can result.
NOTE The decomposition of 1,1,2,2-tetrachoroethane can be eliminated by acidifying the water in the
headspace vial with H SO to pH <2 and using Na SO as salt. But remember that the acid has an immense
2 4 2 4
influence on the life span of the column and the injector.
5.5 Interferences during gas chromatography and mass spectrometry
To rectify interferences that are typically caused by the injection system or by inadequate separation,
enlist experts and observe the manufacturer information in the apparatus manuals. The performance
and stability of the analysis system shall be checked regularly (e.g. by measuring reference solutions of
known composition).
Performance data from an interlaboratory trial held in 2013 are provided in Annex D.
6 Reagents
6.1 General
Unless otherwise indicated, reagents to be used are of purity grade “for analysis” or “for residue
analysis”.
6.2 Water, complying with the requirements of ISO 3696, grade 1 or equivalent without any interfering
blank values.
6.3 Operating gases for gas chromatograph and mass spectrometer, of high purity and according
to the required specification of the manufacturer of the instrumentation, e.g. helium, minimum purity
99,996 %.
6.4 Salts, e.g. sodium sulfate, Na SO , sodium chloride, NaCl.
2 4
6.5 Solvents, for the preparation of stock solutions and as solubilizers in aqueous reference solutions,
e.g. methanol, CH OH, or dimethylformamide (DMF), C H NO.
3 3 7
4 © ISO 2018 – All rights reserved
ISO 20595:2018(E)
6.6 Reference compounds, every compound to be analysed shall be of defined purity.
6.7 Internal standard, for examples of suitable internal standards, see Annex B.
6.8 Examples of stock and standard solutions
6.8.1 Stock solution
The stock solution shall be produced by corresponding dilution of the individual compounds in e.g.
methanol (6.5) or from certified standard mixtures. The concentration of every individual compound is
e.g. 100 µg/ml in methanol (6.5).
Keep the stock solutions at a temperature not exceeding 6 °C and protect them from light.
They are stable for at least 12 months.
6.8.2 Intermediate dilutions (spiking solutions)
Intermediate dilutions (spiking solutions) for the preparation of aqueous multi-component solutions
for calibration over the total process (6.8.4) are produced by dilution of the stock solution (6.8.1) with
a solvent (6.5). For example, use a microlitre syringe (7.7) to add between 5 µl and 500 µl of each of the
required stock solution (6.8.1) in a 10 ml volumetric flask (7.9) filled about half-full with methanol and
then fill up to the mark.
The concentrations in methanol are then between 0,05 µg/ml and 5 µg/ml.
Keep the intermediate dilutions at a temperature not exceeding 6 °C and protect them from light.
They are stable for at least 6 months.
6.8.3 Solution of the internal standards
Prepare the solution by corresponding dilutions of the internal standards (6.7) with methanol (6.5),
each component e.g. 1 µg/ml in methanol.
6.8.4 Aqueous multi-component solution for the calibration
The aqueous multi-component solutions (reference solutions) for the calibration can be produced as
follows.
— Pour a defined volume of e.g. 10 ml water (6.2) in an e.g. 20 ml headspace vial (7.8) and add a defined
volume of e.g. 10 µl of the relevant spiking solution (6.8.2) directly into the water.
— Then add a defined volume of e.g. 10 µl of the internal standard solution (6.8.3) directly into the
water (6.2).
— Close the headspace vial (7.8) with the closing cap directly after the spiking and shake.
If salt is to be added, this is done before adding the water. The addition of salt (6.4) close to saturation
(e.g. 3 g NaCl or 4 g Na SO in 10 ml, respectively) is recommended to minimize matrix effects.
2 4
Alternatively, the spiking solution (6.8.2) and internal standard solution (6.8.3) can also be added via
the septum. This will not result in losses; nevertheless, the quality of the septa used should be ensured
by blank samples.
It is recommended that the spiking volume be kept constant.
The aqueous multi-component solutions for the calibration can also be prepared in volumetric
flasks (7.9). Ensure that no losses result due to pipetting and homogenization. Stir the solution for at
least 10 s. Take care of a thorough mixing but avoid the formation of a turbulence funnel.
ISO 20595:2018(E)
6.9 Sodium thiosulfate pentahydrate, Na S O ∙5H O.
2 2 3 2
NOTE Ascorbic acid can also be used for the neutralizing of the chlorine as far as validated.
7 Apparatus
7.1 General
Equipment or glass parts that come into contact with the water sample shall be free of the compounds
to be analysed and free of residues that can cause interfering blank values. This can be attained by
cleaning the glass equipment.
7.2 Sample bottles, e.g. narrow-necked flat-bottomed bottles with glass stoppers, preferably brown
glass bottles, nominal volume e.g. 250 ml or less.
7.3 Dry cabinet.
7.4 Gas chromatograph (GC), with mass spectrometer (MS) and headspace (HS) sampler.
7.5 Capillary columns, with e.g. (medium-)polar stationary phase, e.g. inner diameter ≤ 0,32 mm,
length about 30 m to 60 m, film thickness 1 µm to 3 µm (phase ratio > 300).
7.6 Magnetic stirring rod, polytetrafluorethylene (PTFE)-encased.
7.7 Microlitre syringes, various nominal volumes e.g. 10 µl, 100 µl, 250 µl, 1 000 µl.
7.8 Headspace vials (HS vial), e.g. 20 ml for automatic sampler.
7.9 Volumetric flasks, nominal volume e.g. 10 ml, 50 ml, 100 ml, e.g. volumetric flasks
ISO 1042 - A10 - C.
7.10 Pipettes.
8 Sampling
Take and handle the samples, taking into account the specifications given in ISO 5667-3, ISO 5667-4,
ISO 5667-5, ISO 5667-6, ISO 5667-10 and ISO 5667-11.
Completely fill the sample bottle (7.2) with the sample.
Ensure a laminar flow during the sampling. Turbulent flows can lead to losses of the substances to be
analysed.
Add sodium thiosulfate pentahydrate (6.9) to water samples likely to contain chlorine, thus obtaining a
concentration of approximately 80 mg/l to 100 mg/l.
Pre-rinsing of the sample bottle (7.2) with sample material is to be avoided, as this can possibly result in
an increased concentration of suspended matter components and also the loss of stabilization reagents
in the sample.
Glass equipment or equipment made from stainless steel or e.g. scoops made from glass shall be used.
Plastic equipment is to be avoided as blank values and analyte losses due to adsorption effects can
occur as a result of this.
It shall be ensured that no interfering compounds get into the sample and no losses occur in the
compounds to be determined (see Clause 5).
6 © ISO 2018 – All rights reserved
ISO 20595:2018(E)
The samples shall be treated and stored in accordance with ISO 5667-3.
If longer storage times are necessary and/or in case of presumed or validated instability, suitable
measures shall be implemented (e.g. preservation with copper sulfate, sodium azide or the
measurement-ready headspace vial shall be frozen horizontally).
9 Procedure
9.1 Sample preparation
The samples shall be handled as the multi-component solutions for the calibration (6.8.4).
In the case of a salt addition, add it to the vial prior to adding the sample.
The samples to be examined are transferred to headspace vials (7.8) while avoiding turbulences.
Subsequently, the internal standard solution (6.8.3) is added. The headspace vials (7.8) shall be tightly
sealed and the salt dissolved by shaking directly afterwards.
The correctness of the headspace analysis depends on maintaining constant phase-volume ratios, i.e.
during the calibration and analysis, the same amounts of water and salt shall always be added to the
headspace vials. Variations due to different batches of vials are compensated by the internal standard.
All samples of a sample sequence are thermostated in succession in the headspace-sampler for a constant
time (e.g. 30 min) and at a constant temperature (e.g. 80 °C) and analysed by gas chromatography with
mass spectrometric detection.
9.2 GC-MS operating conditions
The GC-MS apparatus (7.4) shall be optimized according to the manufacturer data. Capillary
columns (7.5) shall be used for the separation (see Annex A).
9.3 Control measures
9.3.1 Blank value control
The flawless state of the reagents and equipment shall be checked daily if analyses are under acquisition
by means of blank value examinations.
For the blank value examination, examine e.g. water (6.2) in the same way as a sample.
Blank values are location specific. The contamination source shall be localized and, if necessary,
eliminated if blank values occur.
Depending on the blank fluctuation, the blank values should not exceed 30 % to 50 % of the lower
application limit of the method.
9.3.2 Control over the total procedure
The quality of the procedure shall be checked daily by means of control examinations.
For this control examination, for example, water (6.2) shall be spiked with the compounds to be
examined (6.8.4) and examined in the same way as a sample (see 9.1). If deviations are determined (e.g.
out-of-control situations from a control chart), the individual process steps shall be monitored.
ISO 20595:2018(E)
9.4 Identification of individual compounds
9.4.1 General
A compound is identified in the sample by comparing the retention times measured under the same
conditions and associated relative intensities of selected identification masses (see Table 2) with those
of the reference compounds in the aqueous multi-component solution for the calibration (6.8.4).
9.4.2 Identification of individual compounds with mass spectrometric detector
Individual compounds are regarded as identified in the sample if:
— the retention time (t ) of the corresponding peak in the total ion current chromatogram or in the
R
single ion chromatogram (SIM) is within t ± 0,5 % or a maximum of ±5 s, compared with the
R
retention times of the relevant compound measured under the same conditions in the total ion
current chromatogram or the individual mass chromatogram of a reference solution;
— the complete mass spectra of the background corrected reference compounds match the spectra
present at the relevant retention time in the chromatogram of the water sample, which is also
background corrected;
— at least the diagnostic ions of the reference compounds (see Table 2) deviate from those of the
compounds to be identified in their relative peak intensities by less than 30 %;
— for some compounds, only two diagnostic ions are available (see Table 2).
Table 2 — Examples of diagnostic ions of reference compounds to be used for identification and
quantification in mass spectrometric detection
Name Retention Target ion Qualifier Qualifier
a
(compounds of Table 1) time ion 1 ion 2
min m/z m/z m/z
vinyl chloride (chloroethene) 2,900 62 64 56
1,1-dichloroethene 5,005 61 96 63/98
1,1,2-trichlorotrifluoroethane 5,008 101 151 103
allyl chloride (3-chloropropene) 5,622 41 39 76
dichloromethane 5,832 84 86 49/51
trans-1,2-dichloroethene 6,335 96 61 63/96/98
methyl tert-butyl ether (MTBE) 6,320 73 57 61
1,1-dichloroethane 7,082 63 83 65
2-chloro-1,3-butadiene 7,258 88 53
(chloroprene)
ethyl tert-butyl ether (ETBE) 7,899 59 87 57
cis-1,2-dichloroethene 8,203 96 61 98
trichloromethane (chloroform) 8,852 83 85 47
1,1,1-trichloroethane 9,234 97 99 117
tetrachloromethane 9,580 117 119 121
(carbon tetrachloride)
benzene 10,020 78 77 50
1,2-dichloroethane 10,060 62 64 98
1,1-dimethylpropyl-methyl ether,
10,282 55 73
tert-amyl methyl ether (TAME)
trichloroethene 11,490 130 95 132
a
The gas chromatographic conditions are listed in Annex C.
8 © ISO 2018 – All rights reserved
ISO 20595:2018(E)
Table 2 (continued)
Name Retention Target ion Qualifier Qualifier
a
(compounds of Table 1) time ion 1 ion 2
min m/z m/z m/z
1,2-dichloropropane 12,020 63 62 76
2,3-dichloropropene 12,145 75 110 77
bromodichloromethane 12,710 83 85 129
cis-1,3-dichloropropene 13,867 75 110 77
toluene 14,764 91 65 92
trans-1,3-dichloropropene 15,398 75 110 77
1,1,2-trichloroethane 15,805 97 83 99
tetrachloroethene 16,289 166 129 164
dibromochloromethane 17,018 129 127 131
1,2-dibromoethane 17,318 107 109
chlorobenzene 18,834 112 77 114
1,1,1,2-tetrachloroethane 19,115 131 117 133
ethyl benzene 19,214 91 106
m-/p-xylene 19,602 91 106
o-xylene 20,805 91 106
vinyl benzene (styrene) 20,906 104 78
tribromomethane (bromoform) 21,439 173 175 171
isopropylbenzene (cumene) 22,092 105 120
n-propylbenzene 23,474 91 120
2-chlorotoluene 23,686 91 126
3-chlorotoluene 23,908 91 126
4-chlorotoluene 24,067 91 126
1,3,5-trimethylbenzene 24,107 105 120
(mesitylene)
1,2,4-trimethylbenzene 25,368 105 120
(pseudocumene)
1,3-dichlorobenzene 26,236 146 111 148
1,4-dichlorobenzene 26,550 146 111 148
1,2-dichlorobenzene 27,836 146 111 148
dichlorodiisopropyl ether 28,963 45 121
hexachloroethane 28,783 117 201
1,3,5-trichlorobenzene 32,260 180 145 182
1,2,4-trichlorobenzene 35,969 180 145 182
hexachlorobutadiene 37,969 225 260 227
naphthalene 37,606 128 102 127
1,2,3-trichlorobenzene 39,589 180 145 182
biphenyl 61,678 154 153
benzene-d6 9,928 84 52
toluene-d8 14,576 98 100
1,2-dichlorobenzene-d4 27,782 152 150
a
The gas chromatographic conditions are listed in Annex C.
The masses listed for the target ions as well as the qualifier ions in Table 2 serve as an orientation
example. The selection of internal standards should be adapted correspondingly to the compound
ISO 20595:2018(E)
group to be analysed. This applies, in particular, to analysis in respect to the recovery rates as well as to
the gas chromatographic step. The internal standards listed are examples. Further internal standards
can be used (see Annex B).
10 Calibration
10.1 General
— A calibration function shall be determined for each compound to be determined. Multi-component
solutions (6.8.4) can be used for this.
— The linear working range shall be determined by measuring at least five points (basic calibration)
for five different concentrations.
— The calibration function of an individual compound only applies to the relevant concentration range.
It depends on the operating conditions of the gas chromatograph and shall be checked regularly.
At least six measuring points shall be determined when selecting a quadratic function.
In routine operation, a two-point calibration can be adequate for a linear function, but shall be checked
in individual cases (e.g. working range, matrix influences). This shall correspond to the basic calibration.
For setting up a calibration function, the reference solutions shall be adapted to the working range to
set up a basic function (for the preparation of reference solutions, see 6.8.4).
See Table 3 for the meaning of the indices in the following text.
Table 3 — Meaning of the indices
Index Meaning
i Compound
e Measuring variables for the calibration
g Total procedure
j Consecutive figure for pairs of values
I Internal standard
10 © ISO 2018 – All rights reserved
ISO 20595:2018(E)
10.2 Calibration with internal standard
The use of an internal standard renders the concentration determination independent of potential
dosing errors during the injection and of various matrix effects.
Errors that can occur due to sample losses during individual steps of the sample preparation are also
partially compensated.
The mass concentration ρ shall be equal for the calibration and for the sample to be analysed.
iI
— The values for y /y (peak area, peak height or integration units) shall be applied for every
ieg Ieg
compound i on the ordinate as a function of the associated mass concentration ρ /ρ .
ieg Ieg
— The value pairs y /y and ρ /ρ are used to determine a linear regression line according to
ieg Ieg ieg Ieg
Formula (1):
y ρ
ieg ieg
=+mb (1)
iIg iIg
y ρ
Ieg Ieg
where
y is the measured value of compound i during calibration as a function of ρ , the unit
ieg ie
depending on the evaluation, e.g. area unit;
y is the measured value of internal standard I during calibration as a function of ρ , the unit
Ieg Ieg
depending on the evaluation, e.g. area unit; all reference solutions contain equal
concentrations of the internal standard;
ρ is the (independent variable) mass concentration of compound i in the reference solution, in
ieg
micrograms per litre (µg/l);
ρ is the (independent variable) mass concentration of internal standard I in the reference
Ieg
solution, in micrograms per litre (µg/l);
m is the slope of the reference line of y /y as a function of the mass concentration y /y
iIg ieg Ieg ieg Ieg
(response factor);
b is the ordinate intercept of the reference line, the unit depending on the evaluation.
iIg
ISO 20595:2018(E)
11 Evaluation
The mass concentrations ρ of the individual compound shall be calculated according to Formula (2):
ig
y
ig
−b
iIg
y
Ig
ρρ= ⋅ (2)
ig Ig
m
iIg
where
ρ is the mass concentration of the analysed compound i in the water sample, in
ig
micrograms per litre (µg/l);
y is the measured value of the analysed compound i in the water sample, e.g. area unit;
ig
y is the measured value of the internal standard I in the water sample, e.g. area unit;
Ig
ρ is the mass concentration of the internal standard I in the water sample, in micrograms
Ig
per litre (µg/l);
b , m see Formula (1).
iIg iIg
12 Expression of results
The analysis results obtained when applying this document are subject to a measurement uncertainty
that is to be considered in the interpretation of the results.
NOTE The relative measurement uncertainty depends on the concentration and the matrix and is greatest in
the lower application range of the method.
The mass concentration of the substances according to Table 1 is indicated in micrograms per litre at
two significant figures.
EXAMPLES
trichloromethane (chloroform) 11 μg/l
tetrachloroethene 4,1 μg/l
o-xylene 0,17 μg/l
13 Test report
The test report shall contain at least the following information:
a) the test method used, together with a reference to
...
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