SIST EN ISO 21253-1:2020

Water quality - Multi-compound class methods - Part 1: Criteria for the identification of target compounds by gas and liquid chromatography and mass spectrometry (ISO 21253-1:2019)

This International Standard gives criteria for mass spectrometric identification of target compounds in water. This document is a guideline for the identification of molecules <1 200 Da. For identification of larger molecules additional investigations are recommended.
This standard shall be used in conjunction with standards developed for the determination of the specific compounds. If the standards for analysing specific compounds give criteria for identification, those criteria shall be followed.

Wasserbeschaffenheit - Gemeinsam erfassbare Stoffgruppen - Teil 1: Kriterien für die Identifizierung von Zielverbindungen mittels Gaschromatographie und Flüssigchromatographie mit Massenspektrometrie-Kopplung (ISO 21253-1:2019)

Dieses Dokument legt Kriterien für die massenspektrometrische Identifizierung von Zielverbindungen in Wasserproben fest und ist im Allgemeinen auf Umweltproben anwendbar. Dieses Dokument ist für die Anwendung in Verbindung mit einer Norm vorgesehen, die für die Bestimmung bestimmter Verbindungen entwickelt wurde. Wenn ein genormtes Verfahren für die Analyse bestimmter Verbindungen Kriterien für die Identifizierung enthält, dann sind diese Kriterien zu befolgen.

Qualité de l'eau - Méthodes d'analyse de composés multi-classes - Partie 1: Critères pour l'identification des composées cibles par chromatographie en phase gazeuse et liquide et spectrométrie de masse (ISO 21253-1:2019)

Le présent document spécifie des critères pour l'identification par spectrométrie de masse de composés cibles dans des échantillons d'eau et est applicable aux échantillons environnementaux en général. Le présent document est destiné à être utilisé en association avec des normes élaborées pour permettre la détermination de composés spécifiques. Si une méthode normalisée d'analyse de composés spécifiques inclut des critères d'identification, ces critères sont appliqués.

Kakovost vode - Metode za več spojin - 1. del: Merila za identifikacijo ciljnih spojin s plinsko in tekočinsko kromatografijo ter masno spektrometrijo (ISO 21253-1:2019)

Ta mednarodni standard podaja merila za identifikacijo ciljnih spojin v vodi na podlagi masne spektrometrije. Ta dokument je smernica za identifikacijo molekul < 1200 Da. Za identifikacijo večjih molekul so priporočene dodatne preiskave. Ta standard se uporablja skupaj s standardi, pripravljenimi za določanje specifičnih spojin. Če standardi za analizo določenih spojin podajajo merila za identifikacijo, je treba ta merila upoštevati.

General Information

• Status: Published
• Public Enquiry End Date: 02-Jan-2019
• Publication Date: 02-Dec-2019
• ICS: 13.060.50 - Examination of water for chemical substances
• ICS: 71.040.50 - Physicochemical methods of analysis
• Technical Committee: KAV - Water quality
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 11-Nov-2019
• Due Date: 16-Jan-2020
• Completion Date: 03-Dec-2019
• Ref Project: EN ISO 21253-1:2019 - Water quality - Multi-compound class methods - Part 1: Criteria for the identification of target compounds by gas and liquid chromatography and mass spectrometry (ISO 21253-1:2019)

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN ISO 21253-1:2020
01-januar-2020
Kakovost vode - Metode za več spojin - 1. del: Merila za identifikacijo ciljnih spojin
s plinsko in tekočinsko kromatografijo ter masno spektrometrijo (ISO 21253-
1:2019)
Water quality - Multi-compound class methods - Part 1: Criteria for the identification of
target compounds by gas and liquid chromatography and mass spectrometry (ISO 21253
-1:2019)
Wasserbeschaffenheit - Gemeinsam erfassbare Stoffgruppen - Teil 1: Kriterien für die
Identifizierung von Zielverbindungen mittels Gaschromatographie und
Flüssigchromatographie mit Massenspektrometrie-Kopplung (ISO 21253-1:2019)
Qualité de l'eau - Méthodes d'analyse de composés multi-classes - Partie 1: Critères
pour l'identification des composées cibles par chromatographie en phase gazeuse et
liquide et spectrométrie de masse (ISO 21253-1:2019)
Ta slovenski standard je istoveten z: EN ISO 21253-1:2019
ICS:
13.060.50 Preiskava vode na kemične Examination of water for
snovi chemical substances
71.040.50 Fizikalnokemijske analitske Physicochemical methods of
metode analysis
SIST EN ISO 21253-1:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN ISO 21253-1:2020

---------------------- Page: 2 ----------------------
SIST EN ISO 21253-1:2020


EN ISO 21253-1
EUROPEAN STANDARD

NORME EUROPÉENNE

October 2019
EUROPÄISCHE NORM
ICS 13.060.50
English Version

Water quality - Multi-compound class methods - Part 1:
Criteria for the identification of target compounds by gas
and liquid chromatography and mass spectrometry (ISO
21253-1:2019)
Qualité de l'eau - Méthodes d'analyse de composés Wasserbeschaffenheit - Gemeinsam erfassbare
multi-classes - Partie 1: Critères pour l'identification Stoffgruppen - Teil 1: Kriterien für die Identifizierung
des composées cibles par chromatographie en phase von Zielverbindungen mittels Gaschromatographie und
gazeuse et liquide et spectrométrie de masse (ISO Flüssigchromatographie mit Massenspektrometrie-
21253-1:2019) Kopplung (ISO 21253-1:2019)
This European Standard was approved by CEN on 9 August 2019.

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, Turkey 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
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 21253-1:2019 E
worldwide for CEN national Members.

---------------------- Page: 3 ----------------------
SIST EN ISO 21253-1:2020
EN ISO 21253-1:2019 (E)
Contents Page
European foreword . 3

2

---------------------- Page: 4 ----------------------
SIST EN ISO 21253-1:2020
EN ISO 21253-1:2019 (E)
European foreword
This document (EN ISO 21253-1:2019) 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 2020, and conflicting national standards shall be
withdrawn at the latest by April 2020.
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.
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, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 21253-1:2019 has been approved by CEN as EN ISO 21253-1:2019 without any
modification.

3

---------------------- Page: 5 ----------------------
SIST EN ISO 21253-1:2020

---------------------- Page: 6 ----------------------
SIST EN ISO 21253-1:2020
INTERNATIONAL ISO
STANDARD 21253-1
First edition
2019-08
Water quality — Multi-compound
class methods —
Part 1:
Criteria for the identification of
target compounds by gas and
liquid chromatography and mass
spectrometry
Qualité de l'eau — Méthodes d'analyse de composés multi-classes —
Partie 1: Critères pour l'identification de composées cibles par
chromatographie en phase gazeuse ou liquide et spectrométrie de
masse
Reference number
ISO 21253-1:2019(E)
©
ISO 2019

---------------------- Page: 7 ----------------------
SIST EN ISO 21253-1:2020
ISO 21253-1:2019(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2019
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: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

---------------------- Page: 8 ----------------------
SIST EN ISO 21253-1:2020
ISO 21253-1:2019(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 2
5 Principle . 3
6 Apparatus . 3
7 Identification of target compounds . 4
7.1 Procedure for identification of organic compounds with chromatography-mass
spectrometry . 4
7.2 Step 1: Chromatographic separation . 5
7.3 Step 2: Mass spectrometric evaluation . 6
7.3.1 Mass spectrometric detection . 6
7.3.2 Selection of diagnostic ions . 6
7.3.3 Assigning identification points . 7
7.4 Step 3: Additional analytical confirmation evaluation . 8
7.5 Reporting the presence of target compounds . 9
7.5.1 Identification . 9
7.5.2 Indication . 9
7.5.3 Absence of the target compounds ( 8 Test report . 9
Annex A (informative) Recommendations for the most commonly used techniques .10
Annex B (normative) Criteria for full scan measurement .12
n n
Annex C (informative) Diagnostic ions to be used for identification using GC-MS and LC-MS .13
Annex D (informative) Examples of calculating identification points .14
Bibliography .21
© ISO 2019 – All rights reserved iii

---------------------- Page: 9 ----------------------
SIST EN ISO 21253-1:2020
ISO 21253-1:2019(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.
A list of all parts in the ISO 21253 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2019 – All rights reserved

---------------------- Page: 10 ----------------------
SIST EN ISO 21253-1:2020
ISO 21253-1:2019(E)

Introduction
The use of gas chromatography (GC) and liquid chromatography (LC) in combination with mass
spectrometric (MS) detection is common in many analytical standards. This detector is a powerful tool
provided it is properly used. This document gives the criteria for the identification of target compounds
in various types of water. This document shall be used in combination with specific analytical standards
or in combination with any GC-MS and LC-MS procedure. The result of the procedure described is
identified, indicated or absent.
NOTE See Annex A for recommendations for the most commonly used techniques.
[5]
This document is generally based on ISO 22892 .
© ISO 2019 – All rights reserved v

---------------------- Page: 11 ----------------------
SIST EN ISO 21253-1:2020

---------------------- Page: 12 ----------------------
SIST EN ISO 21253-1:2020
INTERNATIONAL STANDARD ISO 21253-1:2019(E)
Water quality — Multi-compound class methods —
Part 1:
Criteria for the identification of target compounds by gas
and liquid chromatography and mass spectrometry
1 Scope
This document specifies the criteria for mass spectrometric identification of target compounds in water
samples and is applicable to environmental samples in general. This document is intended to be used
in conjunction with standards developed for the determination of specific compounds. If a standard
method for analysing specific compounds includes criteria for identification, those criteria are followed.
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 6107 (all parts), Water quality — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 6107 (all parts) and the
following 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
diagnostic ion
selected fragment ion, molecular ion or other characteristic ion from the mass spectrum of the target
compound (3.7) with the highest possible specificity
[SOURCE: ISO 22892:2006, 3.6]
3.2
identification point
result of mass spectrometric investigation or other investigations/information to identify a component
in environmental matrices
[SOURCE: ISO 22892:2006, 3.7]
3.3
relative retention time
ratio between the retention time of the target compound (3.7) and the retention time of the retention
time standard (3.4)
[SOURCE: ISO 22892:2006, 3.4]
© ISO 2019 – All rights reserved 1

---------------------- Page: 13 ----------------------
SIST EN ISO 21253-1:2020
ISO 21253-1:2019(E)

3.4
retention time standard
compound that is added to the sample (or to the sample extract) and to the calibration standard solution,
and used to calculate the relative retention times (3.3) of the target compounds (3.7)
[SOURCE: ISO 22892:2006, 3.3]
3.5
selected ion monitoring
SIM
measurement of the intensity of selected diagnostic ions (3.1) only
3.6
standard compound
target compound (3.7) with the highest possible purity, which can be used as a reference during the
analysis
Note 1 to entry: Any impurities should not have influence on the mass spectrum of the standard compound.
[SOURCE: ISO 22892:2006, 3.2]
3.7
target compound
selected component, the presence or absence of which is being established
Note 1 to entry: This definition can also apply to a derivative of the original compound which is formed during an
intentional derivatization procedure.
[SOURCE: ISO 22892:2006, 3.1]
3.8
calibration standard
solution prepared from a secondary standard and/or stock solutions and used to calibrate the response
of the instrument with respect to analyte concentration
[SOURCE: ISO 18073:2004, 3.1.2]
3.9
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]
4 Abbreviated terms
APCI atmospheric pressure chemical ionization
CI chemical ionization
Da Dalton
ECD electron capture detector
EI electron ionization
EI-GC-MS electron ionization-gas chromatography-mass spectrometry
ESI electrospray ionization
2 © ISO 2019 – All rights reserved

---------------------- Page: 14 ----------------------
SIST EN ISO 21253-1:2020
ISO 21253-1:2019(E)

FWHM full width at half maximum
GC gas chromatography
GC-MS gas chromatography-mass spectrometry
HRMS high resolution mass spectrometry
LC liquid chromatography
LC-MS liquid chromatography-mass spectrometry
mDa milliDalton
MRM multiple reaction monitoring
MS mass spectrometry
n
MS mass spectrometry
MTBE methyl tertiary-butyl ether
m/z mass to charge ratio
NPD nitrogen-phosphorus detector
OCP organo chlorine pesticides
PFPD pulsed flame photometric detector
PID photoionization detector
SIM selected ion monitoring
S/N signal to noise ratio
SRM selected reaction monitoring
TAME tertiary amyl methyl ether
UV/Vis ultraviolet – visible spectroscopy
5 Principle
A target compound is identified if the measured values meet the criteria specified in this document or in
the standard in which the procedures are described to analyse the target compound. Criteria are based
on the relative retention times and the intensity ratio of diagnostic ions, and other relevant factors.
Additional information regarding diagnostic ions from specific international standards on the analysis
of the target compound can be used. The principle of identification points is used (see Annex D).
6 Apparatus
As this document is complementary to other standards using GC-MS and LC-MS, it is assumed that the
instrumentation used meets the requirements of those standards and a detailed description is not
within the scope of this document. The minimum acquisition requirements for low resolution and high
resolution mass spectrometry are summarized in Tables 1 and 2.
© ISO 2019 – All rights reserved 3

---------------------- Page: 15 ----------------------
SIST EN ISO 21253-1:2020
ISO 21253-1:2019(E)

Table 1 — Minimum acquisition requirements for low resolution mass spectrometry
Mass range: Peaks (masses) with a S/N < 3 are not taken into consideration and the lower
end of the scan range is limited to 35 (to avoid the measurement of oxygen and
nitrogen) to the highest mass of the target compound +10 unified atomic mass
units (u) in full scan measurements.
Scan rate: Minimum of 7 scans per peak.
Scan mode: Full scan or SIM.
Mass resolution: To be tuned on nominal resolution, the peak width at half-height of every tune
mass should not exceed 0,7 DA.
Table 2 — Minimum acquisition requirements for high resolution mass spectrometry
Scan rate: Minimum of 7 scans per peak.
Mass resolution: The resolution shall be greater the 10 000 FWHM for the used mass range.
Mass accuracy: The mass accuracy should be ≤5 ppm.
7 Identification of target compounds
IMPORTANT — The equipment shall be operated, and the determination shall be carried out by
suitably trained staff.
7.1 Procedure for identification of organic compounds with chromatography-mass
spectrometry
The procedure to qualify a component consists of three steps (see the flow scheme in Figure 1).
7.1.1 Step 1
Chromatographic evaluation (see 7.2): the relative retention time shall fulfil the specified criteria.
Proceed to step 2 only if step 1 is positive.
7.1.2 Step 2
Mass spectrometric evaluation (see 7.3): gathering identification points using mass spectrometric data.
[1]
For qualification, the principle of identification points is used (see EN 16693 ).
Identification points can be obtained from mass spectrometric data, but also using other analytical
information.
7.1.3 Step 3
Additional analytical confirmation evaluation (see 7.4).
The following classification can be obtained.
a) Identified (see 7.5.1): The target compound is present in the analysed extract if at least
3 identification points are obtained.
b) Indicated (see 7.5.2): The target compound may be present if only 1 or 2 identification points are
obtained.
c) Absent (below the detection limit) (see 7.5.3): No identification points are obtained using mass
spectrometry.
In case the classification result "indication" is unwanted, then any result with less than 3 identification
points shall be regarded as not identified.
4 © ISO 2019 – All rights reserved

---------------------- Page: 16 ----------------------
SIST EN ISO 21253-1:2020
ISO 21253-1:2019(E)

Figure 1 — Flow scheme for the identification of a target compound using three steps
7.2 Step 1: Chromatographic separation
For GC-MS procedures, the gas chromatographic separation shall be carried out using capillary or a
packed column. For LC-MS procedures, the chromatographic separation shall be carried out using a
© ISO 2019 – All rights reserved 5

---------------------- Page: 17 ----------------------
SIST EN ISO 21253-1:2020
ISO 21253-1:2019(E)

suitable LC column. The minimum acceptable retention time for the analyte under examination shall
be twice the retention time corresponding to the void volume of the column. The (relative) retention
time of the analyte in the sample shall match the (relative) retention time of the calibration standard
within a specified retention time window. The retention time window shall be commensurate with the
resolving power of the chromatographic system. The ratio of the chromatographic retention time of
the analyte to that of the retention time standard, i.e. the relative retention time of the analyte, shall
correspond to that of the calibration solution at a tolerance of ±2,5 % for LC and ±0,5 % for GC.
NOTE If specific retention time criteria are given in another standard, these can be followed.
7.3 Step 2: Mass spectrometric evaluation
7.3.1 Mass spectrometric detection
Mass spectrometric detection shall be carried out by employing MS-techniques such as recording of full
n
mass spectra (full scan) or selected ion monitoring (SIM), as well as MS techniques such as selected
n
reaction monitoring (SRM), multiple reaction monitoring (MRM) or other suitable MS or MS techniques
in combination with appropriate ionization modes. In high-resolution mass spectrometry (HRMS), the
resolution shall typically be greater than 10 000 FWHM for the entire mass range.
a) Full scans: When mass spectrometric determination is performed by the recording of full scan
spectra, the presence of all measured diagnostic ions (the molecular ion, characteristics adducts of
the molecular ion, characteristic fragment ions and isotope ions) with a relative intensity of more
than 10 % in the reference spectrum of the calibration standard is obligatory. In HRMS, a partial
scan (of limited mass range) may be adequate to yield sufficient diagnostic ions for identification.
b) SIM: When mass spectrometric determination is performed by fragmentation, the molecular
ion can be one of the selected diagnostic ions (the molecular ion, characteristics adducts of the
molecular ion, characteristic fragment ions and the isotope ions). Whenever possible, the selected
diagnostic ions should be independent from each other, for example not exclusively originate from
the same part of the molecule, nor exclusively be isotope ions. The S/N ratio for each diagnostic ion
shall be ≥ 3:1.
c) Full scan and SIM: The relative intensities of the detected ions, expressed as a percentage of the
intensity of the most intense ion or transition, shall correspond to those of the calibration standard,
either from calibration standard solutions or from spiked samples, at comparable concentrations,
measured under the same conditions, within the tolerances given in Table 3.
Table 3 — Maximum permitted tolerances for relative ion intensities using a range of mass
spectrometric techniques
Maximum allowed tolerance in Maximum allowed tolerance
Relative intensity
n n n
EI-GC-MS CI-GC-MS, CI-GC-MS , EI-GC-MS , LC-MS, LC-MS
>50 % to 100 % ±10 %
>20 % to 50 % ±15 % ±30 %
>10 % to 20 % ±20 %
≤10 % ±50 % ±50 %
7.3.2 Selection of diagnostic ions
If available, three diagnostic ions shall be selected for each target compound. Their intensities shall be
determined in the calibration standard solution either from a calibration standard solution or from
spiked samples at comparable concentrations measured under the same conditions, as the peak area
or peak height of the corresponding extracted ion current chromatograms. Their intensities shall be
determined using at least three injections. The relative intensities are calculated as the ratio of the
determined peak heights (or areas) and the peak height (or area) of the most intensive diagnostic ion.
NOTE Due to overloading, the ratios of the diagnostic ions can change.
6 © ISO 2019 – All rights reserved

---------------------- Page: 18 ----------------------
SIST EN ISO 21253-1:2020
ISO 21253-1:2019(E)

Diagnostic ions may also be specified in the standard method being used. It is not always possible to
obtain three diagnostic ions (for instance for polycyclic aromatic hydrocarbons). In that case, select the
[5]
available ions. Diagnostic ions should have a high “uniqueness value” (see ISO 22892 ). Annex C gives
selection criteria for diagnostic ions.
Co-eluting substances may influence the peak shape. As long as the peak of interest can be separately
integrated, it may be used.
Criteria for the retention time of the selected diagnostic ions are related to the peak maxima of the
extracted ion current chromatograms.
Diagnostic ions should originate from the analyte under investigation only. This implies that,
theoretically, all diagnostic ions belonging to one and the same analyte have the same retention time. If
the retention time of one selected diagnostic ion differs from the retention times of the other diagnostic
ions from the same analyte, a co-eluting substance or a partly-separated substance giving the same
mass may be present. In this case, the particular diagnostic ion cannot be used.
The accuracy of the retention time depends on the number of scans within the chromatographic peak
and hence, on the scan rate. Because the scan rate is limited, small differences in the retention times
of the diagnostic ions should be allowed. A suitable criterion for the allowed difference in retention
times of the diagnostic ions of an analyte shall not be greater than 40 % of the peak width at half the
peak height in a single run. Therefore, the differences in retention times of the peak maxima of all the
selected diagnostic ions in the extracted ion current chromatograms belonging to the same analyte
shall not be greater than 40 % of the peak width at half the peak height. For most analyses, whether GC
or LC, this means an acceptable difference of 1 s. These criteria apply for both the calibration standard
solution and the sample.
7.3.3 Assigning identification points
The qualification of the results is different depending on the mass spectrometric technique used.
When full scan spectra are recorded, a minimum of three ions shall be present with a relative intensity
of ≥10 % of the base peak. The molecular ion shall be included if it is present in the re
...

SLOVENSKI STANDARD
oSIST prEN ISO 21253-1:2018
01-december-2018
.DNRYRVWYRGH0HWRGH]DYHþVSRMLQGHO0HULOD]DLGHQWLILNDFLMRFLOMQLKVSRMLQ
VSOLQVNRLQWHNRþLQVNRNURPDWRJUDILMRWHUPDVQRVSHNWURPHWULMR,62',6

Water quality - Multi-compound class methods - Part 1: Criteria for the identification of
target compounds by gas and liquid chromatography and mass spectrometry (ISO/DIS
21253-1:2018)
Wasserbeschaffenheit - Multi-Class-Verfahren - Teil 1: Anleitung für die Identifizierung
von Zielverbindungen durch Gas- und Flüssigchromatographie und
Massenspektrometrie (ISO/DIS 21253-1:2018)
Qualité de l'eau - Méthodes d'analyse de composés multi-classes - Partie 1: Critères
pour l'identification des composées cibles par chromatographie en phase gazeuse et
liquide et spectrométrie de masse (ISO/DIS 21253-1:2018)
Ta slovenski standard je istoveten z: prEN ISO 21253-1
ICS:
13.060.50 3UHLVNDYDYRGHQDNHPLþQH Examination of water for
VQRYL chemical substances
71.040.50 Fizikalnokemijske analitske Physicochemical methods of
metode analysis
oSIST prEN ISO 21253-1:2018 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN ISO 21253-1:2018

---------------------- Page: 2 ----------------------
oSIST prEN ISO 21253-1:2018
DRAFT INTERNATIONAL STANDARD
ISO/DIS 21253-1
ISO/TC 147/SC 2 Secretariat: DIN
Voting begins on: Voting terminates on:
2018-10-12 2019-01-04
Water quality — Multi-compound class methods —
Part 1:
Criteria for the identification of target compounds by gas
and liquid chromatography and mass spectrometry
Qualité de l'eau — Méthodes de composés multi-class —
Partie 1: Critères pour l'identification des composées cibles par chromatographie en phase gazeuse et
liquide et spectrométrie de masse
ICS: 13.060.50
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 21253-1:2018(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
PROVIDE SUPPORTING DOCUMENTATION. ISO 2018

---------------------- Page: 3 ----------------------
oSIST prEN ISO 21253-1:2018
ISO/DIS 21253-1:2018(E)

COPYRIGHT PROTECTED DOCUMENT
© 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

---------------------- Page: 4 ----------------------
oSIST prEN ISO 21253-1:2018
ISO/DIS 21253-1:2018(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms and their meaning . 2
5 Principle . 3
6 Apparatus . 3
7 Identification of target compounds . 4
7.1 Chromatography-mass spectrometry procedure . 4
7.1.1 Step 1 (see 7.2) . 4
7.1.2 Step 2 (see 7.3) . 4
7.1.3 Step 3 (see 7.4) . 4
7.2 Step 1: Chromatographic separation . 5
7.3 Step 2: Mass spectrometric evaluation . 6
7.3.1 Mass spectrometric detection . 6
7.3.2 Selection of diagnostic ions (part of step 2) . 6
7.3.3 Assigning identification points . 7
7.4 Step 3: Additional analytical confirmation evaluation . 9
7.5 Reporting the presence of target compounds . 9
7.5.1 Identification . 9
7.5.2 Indication . 9
7.5.3 Absence of the target compounds (< detection limit) . 9
8 Test report . 9
Annex A (informative) Recommendations for the most commonly used techniques .10
Annex B (normative) Criteria for full scan measurement .12
n n
Annex C (informative) Diagnostic ions to be used for identification using GC-MS and LC-MS .13
Annex D (informative) Examples of calculating identification points .14
Bibliography .20
© ISO 2018 – All rights reserved iii

---------------------- Page: 5 ----------------------
oSIST prEN ISO 21253-1:2018
ISO/DIS 21253-1:2018(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.
A list of all parts in the ISO 21253 series can be found on the ISO website.
iv © ISO 2018 – All rights reserved

---------------------- Page: 6 ----------------------
oSIST prEN ISO 21253-1:2018
ISO/DIS 21253-1:2018(E)

Introduction
In many analytical standards, use is made of gas chromatography (GC) and liquid chromatography (LC)
in combination with mass spectrometric (MS) detection. This detector is a powerful tool provided it is
properly used. In this document criteria are given for the identification of target compounds in various
types of water. This document can be used in combination with specific analytical standards or in
combination with any GC-MS and LC-MS procedure. The result of the procedure described is: identified,
indicated or absent.
[5]
This document is generally based on ISO 22892 .
The given identification criteria are in line with Commission Decision 2002/657/EC of 12 August 2002
implementing Council Directive 96/23/EC concerning performance of analytical methods and the
[6]
interpretation of results. [Off. J. Eur. Commun. 2002, L221-228] .
© ISO 2018 – All rights reserved v

---------------------- Page: 7 ----------------------
oSIST prEN ISO 21253-1:2018

---------------------- Page: 8 ----------------------
oSIST prEN ISO 21253-1:2018
DRAFT INTERNATIONAL STANDARD ISO/DIS 21253-1:2018(E)
Water quality — Multi-compound class methods —
Part 1:
Criteria for the identification of target compounds by gas
and liquid chromatography and mass spectrometry
1 Scope
This document gives criteria for mass spectrometric identification of target compounds in water samples
and may be applied to environmental samples in general. This document shall be used in conjunction
[3]
with a standard developed for the determination of the specific compounds, for example, ISO 17943
[1]
for volatile organic substances or ISO 16693 for determination of organochlorine pesticide (OCP). If
the standard method for analysing specific compounds includes criteria for identification, those criteria
shall be followed.
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/DIS 21253-2, Water quality — Multi-compound class methods — Part 2: Criteria for the quantitative
determination of organic substances using a multi-compound class analytical method
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
3 Terms and definitions
For the purposes of this document, the terms and definitions given in the ISO 6107 series and the
following 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
diagnostic ion
selected fragment ion, molecular ion or other characteristic ion from the mass spectrum of the target
[5]
compound with the highest possible specificity[SOURCE: ISO 22892:2006, 3.6]
3.2
identification point
result of mass spectrometric investigation or other investigations/information to identify a component
[5]
in environmental matrices[SOURCE: ISO 22892:2006, 3.7]
3.3
relative retention time
ratio between the retention time of the target compound and the retention time of the retention time
[5]
standard[SOURCE: ISO 22892:2006, 3.4]
© ISO 2018 – All rights reserved 1

---------------------- Page: 9 ----------------------
oSIST prEN ISO 21253-1:2018
ISO/DIS 21253-1:2018(E)

3.4
retention time standard
compound that is added to the sample (or to the sample extract) and to the calibration standard
solution, and used to calculate the relative retention times of the target compounds[SOURCE:
[5]
ISO 22892:2006, 3.3]
3.5
selected ion monitoring/SIM
measurement of the intensity of selected diagnostic ions only
3.6
standard compound
target compound with the highest possible purity, which can be used as a reference during the analysis
Note 1 to entry: Any impurities should not have influence on the mass spectrum of the standard compound.
[5]
[SOURCE: ISO 22892:2006, 3.2]
3.7
target compound
selected component, the presence or absence of which is being established
Note 1 to entry: This definition can also apply to a derivative of the original compound which is formed during an
intentional derivatization procedure.
[5]
[SOURCE: ISO 22892:2006, 3.1]
3.8
calibration standard
solution prepared from a secondary standard and/or stock solutions and used to calibrate the response
[4]
of the instrument with respect to analyte concentration[SOURCE: ISO 18073:2004, 3.1.2]
3.9
calibration solution
solution used to calibrate the instrument, prepared from (a) stock solution(s) or from a certified
[2]
standard[SOURCE: ISO 17294-1:2004, 3.4]
4 Abbreviated terms and their meaning
LC Liquid chromatography
GC Gas chromatography
MS Mass spectrometry
GC-MS Gas chromatography-mass spectrometry
LC-MS Liquid chromatography-mass spectrometry
ESI Electrospray ionization
APCI Atmospheric pressure chemical ionization
SIM Selected ion monitoring
SRM Selected reaction monitoring
MRM Multiple reaction monitoring
S/N Signal to noise ratio
2 © ISO 2018 – All rights reserved

---------------------- Page: 10 ----------------------
oSIST prEN ISO 21253-1:2018
ISO/DIS 21253-1:2018(E)

EI Electron ionization
EI-GC-MS Electron ionization-Gas chromatography-Mass spectrometry
CI Chemical ionization
CI-GC-MS Chemical ionization-Gas chromatography-Mass spectrometry
HRMS High resolution mass spectrometry
FWHM Full width at half maximum
n
MS- MS Mass spectrometry-Mass spectrometry
mDA milliDalton
OCP Organo chlorine pesticides
PCB Polychlorinated biphenyls
PAH Polycyclic aromatic hydrocarbons
LR-MS Low resolution mass spectrometry
MTBE Methyl tertiary-butyl ether
TAME Tertiary amyl methyl ether
ECD Electron capture detector
PFPD Pulsed flame photometric detector
NPD Nitrogen-phosphorus detector
PID Photoionization detector
UV/Vis Ultraviolet – visible spectroscopy
m/z Mass to charge ratio
5 Principle
A target compound is identified if the measured values meet the criteria specified in this document or
in the standard in which the procedures are described to analyse the target compound. Criteria are
based on the relative retention times and the intensity of diagnostic ions, and other relevant factors.
Additional information regarding diagnostic ions from specific international standards on the analysis
of the target compound can be used. The principle of identification points is used.
6 Apparatus
As this document is complementary to other standards using GC-MS and LC-MS, it is assumed that
the instrumentation used meets the requirements of those standards and a detailed description is
not within the scope of this document. Suitable quality assurance requirements are set out in ISO/
IEC 17025.
© ISO 2018 – All rights reserved 3

---------------------- Page: 11 ----------------------
oSIST prEN ISO 21253-1:2018
ISO/DIS 21253-1:2018(E)

Table 1 — Minimum acquisition requirements for low resolution mass spectrometry
Mass range: Peaks (masses) with a S/N < 3 are not taken into consideration and the lower
end of the scan range is limited to 35 (to avoid the measurement of oxygen
and nitrogen) to the highest mass of the target compound + 10 unified atomic
mass units (u) in full scan measurements.
Scan rate: Minimum of 7 scans per peak.
Scan mode: Full scan or SIM.
Mass resolution: To be tuned on nominal resolution, the peak width at half-height of every
tune mass should not exceed 0,7 DA.
Table 2 — Minimum requirements for high resolution mass spectrometry
Scan rate: Minimum of 7 scans per peak.
Mass resolution: The resolution shall be greater the 10 000 FWHM for the used mass range.
Mass accuracy: The mass accuracy should be ≤ 5 ppm.
7 Identification of target compounds
IMPORTANT — The equipment shall be operated and the determination shall be carried out by
suitably trained staff.
7.1 Chromatography-mass spectrometry procedure
The procedure to qualify a component consists of three steps (see the flow scheme in Figure 1):
7.1.1 Step 1 (see 7.2)
Chromatographic evaluation: the relative retention time shall fulfil the specified criteria.
Only if step 1 is positive, then proceed to step 2.
7.1.2 Step 2 (see 7.3)
Mass spectrometric evaluation: gathering identification points using mass spectrometric data. For
[1]
qualification, the principle of identification points is used (see ISO 16693 ).
Identification points can be obtained from mass spectrometric data, but also using other analytical
information.
7.1.3 Step 3 (see 7.4)
Additional analytical confirmation evaluation.
Then the following classification can be obtained:
a) Identification (see 7.5.1): The target compound is present in the analysed extract and at least
3 identification points are obtained.
b) Indication (see 7.5.2): The target compound may be present and only 1 or 2 identification points are
obtained.
c) Absence (below the detection limit) (see 7.5.3): No identification points are obtained using mass
spectrometry.
In case the classification result ‘indication’ is unwanted, then any result with less than 3 identification
points shall be regarded as not identified.
4 © ISO 2018 – All rights reserved

---------------------- Page: 12 ----------------------
oSIST prEN ISO 21253-1:2018
ISO/DIS 21253-1:2018(E)

Figure 1 — Flow Scheme for the identification of a target compound using three steps
7.2 Step 1: Chromatographic separation
For GC-MS procedures, the gas chromatographic separation shall be carried out using capillary or
a packed column. For LC-MS procedures, the chromatographic separation shall be carried out using
asuitable LC column. The minimum acceptable retention time for the analyte under examination shall
be twice the retention time corresponding to the void volume of the column. The (relative) retention
time of the analyte in the test portion shall match the (relative) retention time of the calibration
standard within a specified retention time window. The retention time window shall be commensurate
with the resolving power of the chromatographic system. The ratio of the chromatographic retention
time of the analyte to that of the internal standard, i.e. the relative retention time of the analyte, shall
correspond to that of the calibration solution at a tolerance of ±2,5 % for LC and ±0,5 % for GC.
NOTE If specific retention time criteria are given in another standard, these can be followed.
© ISO 2018 – All rights reserved 5

---------------------- Page: 13 ----------------------
oSIST prEN ISO 21253-1:2018
ISO/DIS 21253-1:2018(E)

7.3 Step 2: Mass spectrometric evaluation
7.3.1 Mass spectrometric detection
Mass spectrometric detection shall be carried out by employing MS-techniques such as recording of
n
full mass spectra (full scans) or selected ion monitoring (SIM), as well as MS-MS techniques such
as selected reaction monitoring (SRM), multiple reaction monitoring (MRM) or other suitable MS
n
or MS-MS techniques in combination with appropriate ionization modes. In high-resolution mass
spectrometry (HRMS), the resolution shall typically be greater than 10,000 FWHM for the entire
mass range.
Full scans: When mass spectrometric determination is performed by the recording of full scan spectra,
the presence of all measured diagnostic ions (the molecular ion, characteristics adducts of the molecular
ion, characteristic fragment ions and isotope ions) with a relative intensity of more than 10 % in the
reference spectrum of the calibration standard is obligatory. In HRMS a partial scan (of limited mass
range) may be adequate to yield sufficient diagnostic ions for identification.
SIM: When mass spectrometric determination is performed by fragmentography, the molecular ion
can be one of the selected diagnostic ions (the molecular ion, characteristics adducts of the molecular
ion, characteristic fragment ions and the isotope ions). Whenever possible the selected diagnostic ions
should be independent from each other, e.g. not exclusively originate from the same part of the molecule,
nor exclusively be isotope ions. The S/N ratio for each diagnostic ion shall be ≥ 3:1.
Full scan and SIM: The relative intensities of the detected ions, expressed as a percentage of the intensity
of the most intense ion or transition, shall correspond to those of the calibration standard, either from
calibration standard solutions or from spiked samples, at comparable concentrations, measured under
the same conditions, within the tolerances given in Table 3.
Table 3 — Maximum permitted tolerances for relative ion intensities using a range of mass
spectrometric techniques
Relative intensity Maximum allowed tolerance in Maximum allowed tolerance
n n n
EI-GC-MS CI-GC-MS, CI-GC-MS , , EI-GC-MS , LC-MS, LC-MS
50 % to 100 % ±10 % ±30 %
20 % to 50 % ±15 %
10 % to 20 % ±20 %
≤ 10 % ±50 % ±50 %
7.3.2 Selection of diagnostic ions (part of step 2)
If available, three diagnostic ions shall be selected for each target compound. Their intensities shall be
determined in the calibration standard solution either from a calibration standard solution or from
spiked samples at comparable concentrations measured under the same conditions, as the peak area
or peak height of the corresponding extracted ion current chromatograms. Their intensities shall be
determined using at least three injections. The relative intensities are calculated as the ratio of the
determined peak heights (or areas) and the peak height (or area) of the most intensive diagnostic ion.
Annex C gives selection criteria for diagnostic ions. Diagnostic ions may also be specified in the
standard method being used. It is not always possible to obtain three diagnostic ions (for instance for
polycyclic aromatic hydrocarbons). In that case, select the available ions. Diagnostic ions should have a
[5]
high "uniqueness value" (see ISO 22892 ). It is suggested that:
— high m/z values should be preferred due to their higher significance;
— even mass fragments are preferred over odd ones;
— if possible, the molecular ion should be selected as one of the diagnostic ions;
6 © ISO 2018 – All rights reserved

---------------------- Page: 14 ----------------------
oSIST prEN ISO 21253-1:2018
ISO/DIS 21253-1:2018(E)

— the intensity of diagnostic ions is preferably higher than 15 % in relation to the base peak in the
spectrum;
— if characteristic isotope clusters are present in the mass spectrum (e.g. chlorine), two diagnostic
ions should be selected from one isotope cluster; isotopes can be very characteristic for complex
compounds, i.e. organotin;
— if during the sample preparation, the target compounds have been derivatized with a reagent with
low specificity, only one of the ions M+ and [M-der]+ should be selected as a diagnostic ion. M+ is the
molecular ion of the derivatized target compound);
— in the selection of the diagnostic ions, possible column artefacts have to be taken into consideration,
avoiding corresponding masses (e.g. m/z 73, m/z 207, m/z 281);
The peak shape and retention time of all measured diagnostic ions shall be identical. Co-eluting
substances may influence the peak shape. As long as the peak of interest can be separately integrated,
it may be used.
Criteria for the retention time of the selected diagnostic ions are related to the peak maxima of the
extracted ion current chromatograms.
Diagnostic ions should originate from the analyte under investigation only. This implies that
theoretically all diagnostic ions belonging to one and the same analyte have the same retention time. If
the retention time of one selected diagnostic ion differs from the retention times of the other diagnostic
ions from the same analyte, a co-eluting substance or a partly-separated substance giving the same
mass may be present. In this case, the particular diagnostic ion cannot be used.
The accuracy of the retention time depends on the number of scans within the chromatographic peak
and hence, on the scan rate. Because the scan rate is limited, small differences in the retention times of
the diagnostic ions should be allowed. A suitable criterion for the allowed difference in retention times
of the diagnostic ions of an analyte shall not be greater than 40 % of the peak width at half the peak
height in a single run. Therefore, the differences in retention times of the peak maxima of all the selected
diagnostic ions in the extracted ion current chromatograms belonging to the same analyte shall not be
greater than 40 % of the peak width at half the peak height. For most analyses, this means an acceptable
difference of 1 s. These criteria apply for both the calibration standard solution and the sample.
NOTE 1 MTBE and TAME have m/z 73 as diagnostic ion.
NOTE 2 Due to overloading, the ratios of the diagnostic ions can change.
7.3.3 Assigning identification points
The qualification of the results is different depending on the mass spectrometric technique used.
When full scan spectra are recorded in single mass spectrometry, a minimum of three ions shall be
present with a relative intensity of ≥ 10 % of the base peak. The molecular ion shall be included if
it is present in the reference spectrum with a relative intensity of ≥ 10 %. If computer aided library
searching is used, critical match factors described in Annex B shall be applied. Variability in the spectra
caused by the sample matrix and the detector performance shall be checked.
When mass fragments are measured using other than full-scan techniques, or library matching is not
possible, a system of identification points shall be used to interpret the data. For the confirmation of any
substance, three identification points are required. Tables 4 and 5 shows the number of identification
points that each of the basic mass spectrometric techniques can earn. However, in order to qualify for
the identification points required for confirmation and the sum of identification points to be calculated:
— at least one ion ratio shall be measured, and
— all relevant measured ion ratios shall meet the criteria described in Table 3, and
© ISO 2018 – All rights reserved 7

---------------------- Page: 15 ----------------------
oSIST prEN ISO 21253-1:2018
ISO/DIS 21253-1:2018(E)

— a maximum of three separate techniques can be combined to achieve the minimum number of
identification points;
— each ion may only be counted once;
— GC-MS using electron impact ionization is regarded as
...