ISO/TS 21231:2019
(Main)Water quality — Characterization of analytical methods — Guidelines for the selection of a representative matrix
Water quality — Characterization of analytical methods — Guidelines for the selection of a representative matrix
This document specifies representative materials suitable for the determination of the performance characteristics, including uncertainty, during the initial assessment of a quantitative method, used in a laboratory, for physico-chemical water analysis. This document focuses on five main types of water: — waters intended for consumption (5.2); — natural waters (5.3); — waste waters (5.4); — marine waters (5.5); — recreational waters (5.6). NOTE Other more specific or less common types of water can be incorporated in any of the above types provided appropriate justifications. The characteristics of the standard matrix are compatible with the characteristics of the samples handled.
Titre manque
Kakovost vode - Karakterizacija analiznih metod - Smernice za izbiro reprezentativnega matriksa
Ta dokument določa reprezentativne materiale, primerne za določanje značilnosti zmogljivosti, vključno z negotovostjo, med začetno oceno kvantitativne metode, uporabljene v
laboratoriju, za fizikalno-kemijsko analizo vode.
Ta dokument se osredotoča na pet glavnih vrst vod:
– vodo, ki je namenjena za pitje (5.2);
– naravno vodo (5.3);
– odpadno vodo (5.4);
– morsko vodo (5.5);
– rekreacijsko vodo (5.6).
OPOMBA: Druge bolj specifične ali manj pogoste vrste vod je mogoče vključiti v katero koli od naštetih vrst z ustrezno utemeljitvijo. Značilnosti standardne matrike so združljive z značilnostmi obravnavanih vzorcev.
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TECHNICAL ISO/TS
SPECIFICATION 21231
First edition
2019-02
Water quality — Characterization of
analytical methods — Guidelines for
the selection of a representative matrix
Reference number
ISO/TS 21231:2019(E)
©
ISO 2019
---------------------- Page: 1 ----------------------
ISO/TS 21231:2019(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: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TS 21231:2019(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 4
5 Influence parameters . 5
5.1 Common parameters for all matrices . 5
5.2 Water intended for consumption . 6
5.3 Natural waters . 6
5.4 Waste waters . 6
5.5 Marine waters . 6
5.6 Recreational waters . 7
6 Selection of characteristic parameters of a matrix . 7
6.1 General . 7
6.2 All waters . 7
6.3 Waters intended for consumption . 7
6.4 Natural waters . 7
6.5 Waste waters . 7
6.6 Marine waters . 8
6.7 Recreational waters . 8
7 Available materials . 8
7.1 General . 8
7.2 Material obtained by reasonable dilution of a real matrix . 8
7.3 Artificial material . 9
7.4 Analyte-specific blank values in matrices. 9
8 Report . 9
Annex A (informative) Characterization of waters intended for human consumption and
mineral waters .10
Annex B (informative) Examples of preparation of artificial matrices and representative
characteristics .11
Annex C (informative) Occurrence of chemical substances in waste water, by industrial
activity sector .23
Annex D (informative) Leachate .32
Bibliography .33
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ISO/TS 21231:2019(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 of 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 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.
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
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ISO/TS 21231:2019(E)
Introduction
This document has been prepared for the validation of analytical methods applied to the water quality
field. It enables a laboratory to determine the characteristics of a material suitable for determination of
the performances of an analytical method itself.
It is not intended to provide an exhaustive inventory of all published recipes, but to propose a selection
of recipes supporting the characterization of the performances of analytical methods used by a
laboratory. For this reason, a restricted number of recipes are proposed. References giving access to
other recipes are available in the Bibliography.
This document includes four recipes for preparing marine waters and five recipes for waste waters
with controlled characteristics.
© ISO 2019 – All rights reserved v
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TECHNICAL SPECIFICATION ISO/TS 21231:2019(E)
Water quality — Characterization of analytical methods —
Guidelines for the selection of a representative matrix
1 Scope
This document specifies representative materials suitable for the determination of the performance
characteristics, including uncertainty, during the initial assessment of a quantitative method, used in a
laboratory, for physico-chemical water analysis.
This document focuses on five main types of water:
— waters intended for consumption (5.2);
— natural waters (5.3);
— waste waters (5.4);
— marine waters (5.5);
— recreational waters (5.6).
NOTE Other more specific or less common types of water can be incorporated in any of the above types
provided appropriate justifications. The characteristics of the standard matrix are compatible with the
characteristics of the samples handled.
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 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples
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 General vocabulary
3.1.1
matrix
set of constituents of the test sample, except the analyte (3.2.1)
Note 1 to entry: By extension, a matrix defines a group of waters characterized by similar analytical behaviour in
relation to the analytical method used.
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ISO/TS 21231:2019(E)
3.1.2
accepted reference value
value that serves as an agreed-upon reference for comparison, and which is derived as:
a) a theoretical or established value, based on scientific principles;
b) an assigned or certified value, based on experimental work of some national or international
organization;
c) a consensus or certified value, based on collaborative experimental work under the auspices of a
scientific or engineering group;
d) when a), b) and c) are not available, the expectation of the (measurable) quantity, i.e. the mean of a
specified population of measurements
Note 1 to entry: In the specific context of this document, the accepted reference value (or conventionally true
value) of the sample is provided according to possibilities by:
— the value from a certified reference material certificate,
— the consensus value obtained from an inter-laboratory comparison,
— the arithmetic mean of the repeated measurement values according to the reference method,
— the target value by adding analyte to a representative matrix of the scope in question.
[SOURCE: ISO 5725-1:1994, 3.5]
3.1.3
reference material
material, sufficiently homogeneous and stable with respect to one or more specified properties, which
has been established to be fit for its intended use in a measurement process
[SOURCE: ISO Guide 35:2017, 3.1]
3.1.4
certified reference material
reference material (3.1.3), accompanied by a certificate, one or more of whose property values are
certified by a procedure which establishes traceability to an accurate realization of the unit in which
the property values are expressed, and for which each certified value is accompanied by an uncertainty
at a stated level of confidence
[SOURCE: ISO/TS 13530:2009, 3.2.7]
3.1.5
assessment procedure
procedure related to the establishment of the specifications for the performance of a new method and/
or experimental verification that a method meets theoretically derived quality criteria
3.2 Terms related to analytical methods
3.2.1
analyte
subject of the analytical method
3.2.2
analytical method
unambiguously written procedure describing all details required to carry out the analysis of the analyte
(3.2.1), namely: scope and field of application, principle and/or reactions, definitions, reagents, apparatus,
analytical procedures, calculations and presentation of results, performance data and test report
[SOURCE: ISO/TS 16489:2006, 3.3]
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ISO/TS 21231:2019(E)
3.2.3
quantitative analytical method
analytical method for measuring the quantity of analyte (3.2.1)contained in the test sample
Note 1 to entry: The result can consist of a quantity in a given quantity of test sample.
3.2.4
limit of detection
output signal or value above which it can be affirmed, with a stated level of confidence, for example
95 %, that a sample is different from a blank sample containing no determinand of interest, and which
could be estimated by different means and shall be verified in the intended matrix
[SOURCE: ISO 6107-2:2006, 60, modified — “and which could be estimated by different means and shall
be verified in the intended matrix” has been added.]
3.2.5
limit of quantification
LOQ
lowest value of a determinand that can be determined with an acceptable level of accuracy, which could
be estimated by different means and shall be verified in the intended matrix
Note 1 to entry: For each matrix, this limit is related to the pair [analyte (3.2.1), method].
3.2.6
reasonable dilution
dilution conditions for reducing the concentration of a substance in a matrix without substantially
modifying the intrinsic characteristics of the matrix
3.2.7
matrix blank values
values of a given parameter obtained using a test conducted on a matrix giving rise to a result below the
limit of detection (3.2.4) for the analyte (3.2.1) in question
3.2.8
scope of the analytical method
combination of the various types of matrix and the analyte (3.2.1) concentration range covered, to
which the analytical method applies
Note 1 to entry: In addition to an indication of all the satisfactory performance conditions for each factor, the
scope of the analytical method may also include warnings in respect of known interferences from other analytes,
or inapplicability to some matrices or conditions.
3.3 Terms related to matrix
3.3.1
influence parameter
intrinsic characteristic of the matrix, independent of the analyte (3.2.1) concentration, a variation of
which is liable to modify the analytical result
3.3.2
representative matrix
sample for which all the intrinsic characteristics are characteristic of a type of water or the source of a
group of samples
3.3.3
salinity
mass in grams of solid substances contained in one kilogram of sea water, when the bromide and iodide
ions are replaced by their chloride equivalent, carbonates converted into oxides and all the organic
matter oxidized
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ISO/TS 21231:2019(E)
3.3.4
leachate
water which has percolated through tipped refuse or other specified permeable material
Note 1 to entry: See Annex D.
[SOURCE: ISO 6107-7:2006, 23]
4 Principle
The purpose of this document is to specify the concept of a representative matrix and its characteristics
with a view to studying the performance of an analytical method.
For each analyte under test, the scope of an analytical method includes all the matrices under test,
their descriptive parameters, and the concentration ranges of the influence parameters for which the
method is applicable. The laboratory should define its requirements beforehand in respect of the scope
of the analytical method, selecting the materials most in line with requirements.
WARNING — The definition of the scope is entirely dependent on the analyst (the validation or
characterization study manager) and their knowledge acquired while developing the method.
It is sometimes preferable to segment a scope rather than seek to validate an overly general
method. In this case, a validation file should be compiled for each scope.
See Figure 1.
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ISO/TS 21231:2019(E)
Figure 1 — Summary flow chart
5 Influence parameters
5.1 Common parameters for all matrices
The following influence parameters are liable to have an impact on analysis procedures. They shall help
classify the types of water on which the laboratory has validated its method or determined performance
characteristics.
— pH;
— ion composition and/or conductivity;
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ISO/TS 21231:2019(E)
— salinity;
— dissolved organic carbon (DOC) and/or total organic carbon (TOC);
— colour or turbidity;
— suspended particular matter (SPM) content.
During the validation or characterization study, it is up to the laboratory to:
— define, for its practice, the characteristic ranges associated with each of the above parameters;
— justify, if applicable, the lack of influence thereof on the characterized method;
— complement this list with other characteristic parameters based on the methods and the source of
the samples analysed, using for example Annex A or Annex C.
5.2 Water intended for consumption
Water intended for human and livestock consumption is water considered to be fit for drinking.
Drinking water belongs to this category. It includes groundwater that has been chlorinated in the
resource.
The minimum additional characteristics to be included for this category are:
— disinfectant presence and content (distributed waters or groundwater chlorinated in the resource);
— CO content (natural mineral water), if relevant to subsequent specified analysis requirements.
2
5.3 Natural waters
Natural waters are waters taken from the natural environment not undergoing to any treatment other
than the addition of reagents for analyte preservation.
Surface waters and groundwater belong to this category. Brackish waters with salinity lower than
30 g/l are incorporated in this category.
Rainwater, which is generally not intended for consumption, are incorporated in this category.
5.4 Waste waters
Waste waters can originate from any combination of household, industrial or commercial activities.
They include collected run-offs and those from any spillage or infiltration from the waste water
collection system, including the contents of storm water tanks or ponds, discharged into collection
systems or into the environment.
NOTE 1 Waste waters can be collected in common systems or in separate systems.
NOTE 2 For the purposes of this document, the definition of waste water also includes untreated sanitary
waters.
NOTE 3 National or local regulations can include lists of substances of concern in relation to sewer discharges.
Annex C gives a list of examples of additional characteristics associated with some sectors of activity.
Some waste waters may have a high salinity.
5.5 Marine waters
Sea water consists of a large number of compounds distributed over the following categories: gases,
particulate matter, colloids, and dissolved elements (see Reference [7]).
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ISO/TS 21231:2019(E)
The dissolved elements consist of 92 natural chemical elements, approximately two-thirds of which
are present in ultra-trace amounts and are difficult to detect. Sea water is characterized in that the
[8]
relative proportions of its 11 main constituents are substantially constant (Dittmar's law ) within
1 %. Dittmar's law can thus be used to determine the salinity of sea water by measuring only one of its
components.
The average salinity of sea water is 35 g/kg. It is generally between 30 g/kg (North Atlantic) and 40 g/
kg (Red Sea) but exhibits extreme values in closed or semi-closed seas (6 g/kg in the Baltic Sea, 330 g/
kg in the Dead Sea). The pH of sea water is approximately 8,2.
5.6 Recreational waters
Recreational waters are bathing, swimming pool, thermal bath and spa waters. They may be sourced
from natural waters or waters intended for human consumption and are characterized, in addition to
the influence parameters defined in 5.2, by the potential presence of specific disinfection products and
by-products, and the potential presence of sulfur compounds.
6 Selection of characteristic parameters of a matrix
6.1 General
For the purposes of characterization of the applicability and the performances of an analytical method
to a matrix, the laboratory shall describe the limits of the ranges associated with the characteristic
parameters discussed in this clause.
6.2 All waters
The parameters are those defined in 5.1.
6.3 Waters intended for consumption
In addition to the characteristics listed in 5.1, waters intended for consumption are characterized by:
— their free and total chlorine content;
— the nature and content of disinfection reagents and by-products;
— their CO content, if relevant.
2
Refer to Annex A for more detailed characterization of waters intended for human consumption.
6.4 Natural waters
In addition to the characteristics listed in 5.1, natural waters are characterized by:
— the sampling location, including the sampling depth;
— the identified surrounding anthropic pressures.
In the case of groundwater used as drinking water resources, which are treated in situ, free and total
chlorine content should be verified.
6.5 Waste waters
In addition to the characteristics listed in 5.1, waste waters are characterized by:
— the original activity sector (see Annex C);
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ISO/TS 21231:2019(E)
— the connected activity sectors in the case of municipal waste water treatment plants (MWWTP)
discharges.
6.6 Marine waters
In addition to the characteristics listed in 5.1, marine waters are characterized by:
— the sampling location, including sampling depth;
— their salinity.
6.7 Recreational waters
In addition to the characteristics listed in 5.1, recreational waters are characterized by:
— the sampling location;
— the nature and content of disinfection reagents and by products.
7 Available materials
7.1 General
The laboratory shall select study matrices for one or more of the above water types from, in order of
preference:
— reference materials if the matrix is sufficiently characterized;
— supernumerary material from interlaboratory tests if stable and sufficiently characterized;
— material obtained by spiking with the real matrix free from the analytes of interest;
— material obtained by spiking a reasonable dilution of a real matrix, after adjusting the characteristics
modified by the dilution;
— material obtained by spiking of an artificial matrix based on a recipe (see Annex B).
At least three different representative samples of each water type should be studied to provide a
realistic evaluation of performance of the method on the selected water type. Wherever possible, the
method performances shall be characterized on a non-artificial sample.
7.2 Material obtained by reasonable dilution of a real matrix
When the laboratory cannot select a real matrix free from analyte(s) of interest, but it is possible to
select a real matrix containing the analyte(s) of interest at a concentration lower than 10× the limit
of quantification (LOQ) defined for the method under examination, a representative matrix can be
prepared by diluting the low-concentration real matrix, so as to lower the concentration of analyte(s) of
interest to less than the LOQ defined for the method.
The dilution factor, f, shall be lower than 10. For this dilution, a water free from analyte(s) of interest
having a similar composition to the chosen matrix (major elements and influence factors) shall be used.
Before dilution, the selected matrix shall be characterized on the basis of the influence parameters
chosen for the study. After dilution, these parameters shall be readjusted if required using solid state
reagents or stock solutions of solid state reagents so that the value of each influence parameter remains
within the scope defined by the laboratory.
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ISO/TS 21231:2019(E)
7.3 Artificial material
Artificial materials can be prepared according to Annex B, after adjusting the influence parameters
selected based on a bibliographic study, and/or on Annex C, within the concentration range defining the
scope of the method.
7.4 Analyte-specific blank values in matrices
For some analytes, such as heavy metals, no analyte-free natural or artificial matrix can be obtained.
After proper justification, the laboratory should study LOQ as follows.
— Determine LOQ on ultrapure water.
MQ
— Calculate LOQ by correcting LOQ using the recovery of the analyte in the intended matric,
water i MQ
i.e. water by using Formula (1):
LOQ
MQ
LOQ = (1)
water i
ρ
water i
where
LOQ is the LOQ of the method for the analyte in water type i;
water i
LOQ is the LOQ of the method for the analyte in ultra pure water;
MQ
is the mean recovery of the method for the analyte in water type i.
ρ
water i
8 Report
The quantitative analytical method assessment report, for a given matrix, shall include, in addition to
the information requested by the assessment procedure:
a) the name of the tested matrix according to the typology defined in Clause 5;
b) the characteristic parameters of the matrix according to Clause 6 and the associated representative
ranges (scope);
c) the influence parameters tested, the justification for their selection and the representative
contents;
d) the source of the matrix and, if applicable, its preparation method.
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ISO/TS 21231:2019(E)
Annex A
(informative)
Characterization of waters intended for human consumption and
mineral waters
Water intended for human consumption produced, is generally characterized by:
— the absence of suspended solids;
— a relatively low organic content (TOC < 4 mg/ l);
— a conductivity at 25 °C between 50 µS/cm and 1 100 µS/cm and
— a pH between 6 and 9.
Waters sampled during the production cycle, or at distribution point, often show traces of oxidants
used to disinfect resource water, usually chlorine, chlorine dioxide or ozone at levels between 0,2 mg/l
and 2 mg/l. Depending on the parameters to
...
SLOVENSKI STANDARD
SIST-TS ISO/TS 21231:2019
01-oktober-2019
Kakovost vode - Karakterizacija analiznih metod - Smernice za izbiro
reprezentativnega matriksa
Water quality - Characterization of analytical methods - Guidelines for the selection of a
representative matrix
Qualité de l'eau - Caractérisation des méthodes d'analyses - Lignes directrices pour la
sélection d'une matrice représentative
Ta slovenski standard je istoveten z: ISO/TS 21231:2019
ICS:
13.060.50 Preiskava vode na kemične Examination of water for
snovi chemical substances
SIST-TS ISO/TS 21231:2019 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST-TS ISO/TS 21231:2019
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SIST-TS ISO/TS 21231:2019
TECHNICAL ISO/TS
SPECIFICATION 21231
First edition
2019-02
Water quality — Characterization of
analytical methods — Guidelines for
the selection of a representative matrix
Reference number
ISO/TS 21231:2019(E)
©
ISO 2019
---------------------- Page: 3 ----------------------
SIST-TS ISO/TS 21231:2019
ISO/TS 21231:2019(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: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
---------------------- Page: 4 ----------------------
SIST-TS ISO/TS 21231:2019
ISO/TS 21231:2019(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 4
5 Influence parameters . 5
5.1 Common parameters for all matrices . 5
5.2 Water intended for consumption . 6
5.3 Natural waters . 6
5.4 Waste waters . 6
5.5 Marine waters . 6
5.6 Recreational waters . 7
6 Selection of characteristic parameters of a matrix . 7
6.1 General . 7
6.2 All waters . 7
6.3 Waters intended for consumption . 7
6.4 Natural waters . 7
6.5 Waste waters . 7
6.6 Marine waters . 8
6.7 Recreational waters . 8
7 Available materials . 8
7.1 General . 8
7.2 Material obtained by reasonable dilution of a real matrix . 8
7.3 Artificial material . 9
7.4 Analyte-specific blank values in matrices. 9
8 Report . 9
Annex A (informative) Characterization of waters intended for human consumption and
mineral waters .10
Annex B (informative) Examples of preparation of artificial matrices and representative
characteristics .11
Annex C (informative) Occurrence of chemical substances in waste water, by industrial
activity sector .23
Annex D (informative) Leachate .32
Bibliography .33
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SIST-TS ISO/TS 21231:2019
ISO/TS 21231:2019(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 of 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 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.
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
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SIST-TS ISO/TS 21231:2019
ISO/TS 21231:2019(E)
Introduction
This document has been prepared for the validation of analytical methods applied to the water quality
field. It enables a laboratory to determine the characteristics of a material suitable for determination of
the performances of an analytical method itself.
It is not intended to provide an exhaustive inventory of all published recipes, but to propose a selection
of recipes supporting the characterization of the performances of analytical methods used by a
laboratory. For this reason, a restricted number of recipes are proposed. References giving access to
other recipes are available in the Bibliography.
This document includes four recipes for preparing marine waters and five recipes for waste waters
with controlled characteristics.
© ISO 2019 – All rights reserved v
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SIST-TS ISO/TS 21231:2019
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SIST-TS ISO/TS 21231:2019
TECHNICAL SPECIFICATION ISO/TS 21231:2019(E)
Water quality — Characterization of analytical methods —
Guidelines for the selection of a representative matrix
1 Scope
This document specifies representative materials suitable for the determination of the performance
characteristics, including uncertainty, during the initial assessment of a quantitative method, used in a
laboratory, for physico-chemical water analysis.
This document focuses on five main types of water:
— waters intended for consumption (5.2);
— natural waters (5.3);
— waste waters (5.4);
— marine waters (5.5);
— recreational waters (5.6).
NOTE Other more specific or less common types of water can be incorporated in any of the above types
provided appropriate justifications. The characteristics of the standard matrix are compatible with the
characteristics of the samples handled.
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 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples
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 General vocabulary
3.1.1
matrix
set of constituents of the test sample, except the analyte (3.2.1)
Note 1 to entry: By extension, a matrix defines a group of waters characterized by similar analytical behaviour in
relation to the analytical method used.
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3.1.2
accepted reference value
value that serves as an agreed-upon reference for comparison, and which is derived as:
a) a theoretical or established value, based on scientific principles;
b) an assigned or certified value, based on experimental work of some national or international
organization;
c) a consensus or certified value, based on collaborative experimental work under the auspices of a
scientific or engineering group;
d) when a), b) and c) are not available, the expectation of the (measurable) quantity, i.e. the mean of a
specified population of measurements
Note 1 to entry: In the specific context of this document, the accepted reference value (or conventionally true
value) of the sample is provided according to possibilities by:
— the value from a certified reference material certificate,
— the consensus value obtained from an inter-laboratory comparison,
— the arithmetic mean of the repeated measurement values according to the reference method,
— the target value by adding analyte to a representative matrix of the scope in question.
[SOURCE: ISO 5725-1:1994, 3.5]
3.1.3
reference material
material, sufficiently homogeneous and stable with respect to one or more specified properties, which
has been established to be fit for its intended use in a measurement process
[SOURCE: ISO Guide 35:2017, 3.1]
3.1.4
certified reference material
reference material (3.1.3), accompanied by a certificate, one or more of whose property values are
certified by a procedure which establishes traceability to an accurate realization of the unit in which
the property values are expressed, and for which each certified value is accompanied by an uncertainty
at a stated level of confidence
[SOURCE: ISO/TS 13530:2009, 3.2.7]
3.1.5
assessment procedure
procedure related to the establishment of the specifications for the performance of a new method and/
or experimental verification that a method meets theoretically derived quality criteria
3.2 Terms related to analytical methods
3.2.1
analyte
subject of the analytical method
3.2.2
analytical method
unambiguously written procedure describing all details required to carry out the analysis of the analyte
(3.2.1), namely: scope and field of application, principle and/or reactions, definitions, reagents, apparatus,
analytical procedures, calculations and presentation of results, performance data and test report
[SOURCE: ISO/TS 16489:2006, 3.3]
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3.2.3
quantitative analytical method
analytical method for measuring the quantity of analyte (3.2.1)contained in the test sample
Note 1 to entry: The result can consist of a quantity in a given quantity of test sample.
3.2.4
limit of detection
output signal or value above which it can be affirmed, with a stated level of confidence, for example
95 %, that a sample is different from a blank sample containing no determinand of interest, and which
could be estimated by different means and shall be verified in the intended matrix
[SOURCE: ISO 6107-2:2006, 60, modified — “and which could be estimated by different means and shall
be verified in the intended matrix” has been added.]
3.2.5
limit of quantification
LOQ
lowest value of a determinand that can be determined with an acceptable level of accuracy, which could
be estimated by different means and shall be verified in the intended matrix
Note 1 to entry: For each matrix, this limit is related to the pair [analyte (3.2.1), method].
3.2.6
reasonable dilution
dilution conditions for reducing the concentration of a substance in a matrix without substantially
modifying the intrinsic characteristics of the matrix
3.2.7
matrix blank values
values of a given parameter obtained using a test conducted on a matrix giving rise to a result below the
limit of detection (3.2.4) for the analyte (3.2.1) in question
3.2.8
scope of the analytical method
combination of the various types of matrix and the analyte (3.2.1) concentration range covered, to
which the analytical method applies
Note 1 to entry: In addition to an indication of all the satisfactory performance conditions for each factor, the
scope of the analytical method may also include warnings in respect of known interferences from other analytes,
or inapplicability to some matrices or conditions.
3.3 Terms related to matrix
3.3.1
influence parameter
intrinsic characteristic of the matrix, independent of the analyte (3.2.1) concentration, a variation of
which is liable to modify the analytical result
3.3.2
representative matrix
sample for which all the intrinsic characteristics are characteristic of a type of water or the source of a
group of samples
3.3.3
salinity
mass in grams of solid substances contained in one kilogram of sea water, when the bromide and iodide
ions are replaced by their chloride equivalent, carbonates converted into oxides and all the organic
matter oxidized
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3.3.4
leachate
water which has percolated through tipped refuse or other specified permeable material
Note 1 to entry: See Annex D.
[SOURCE: ISO 6107-7:2006, 23]
4 Principle
The purpose of this document is to specify the concept of a representative matrix and its characteristics
with a view to studying the performance of an analytical method.
For each analyte under test, the scope of an analytical method includes all the matrices under test,
their descriptive parameters, and the concentration ranges of the influence parameters for which the
method is applicable. The laboratory should define its requirements beforehand in respect of the scope
of the analytical method, selecting the materials most in line with requirements.
WARNING — The definition of the scope is entirely dependent on the analyst (the validation or
characterization study manager) and their knowledge acquired while developing the method.
It is sometimes preferable to segment a scope rather than seek to validate an overly general
method. In this case, a validation file should be compiled for each scope.
See Figure 1.
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Figure 1 — Summary flow chart
5 Influence parameters
5.1 Common parameters for all matrices
The following influence parameters are liable to have an impact on analysis procedures. They shall help
classify the types of water on which the laboratory has validated its method or determined performance
characteristics.
— pH;
— ion composition and/or conductivity;
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— salinity;
— dissolved organic carbon (DOC) and/or total organic carbon (TOC);
— colour or turbidity;
— suspended particular matter (SPM) content.
During the validation or characterization study, it is up to the laboratory to:
— define, for its practice, the characteristic ranges associated with each of the above parameters;
— justify, if applicable, the lack of influence thereof on the characterized method;
— complement this list with other characteristic parameters based on the methods and the source of
the samples analysed, using for example Annex A or Annex C.
5.2 Water intended for consumption
Water intended for human and livestock consumption is water considered to be fit for drinking.
Drinking water belongs to this category. It includes groundwater that has been chlorinated in the
resource.
The minimum additional characteristics to be included for this category are:
— disinfectant presence and content (distributed waters or groundwater chlorinated in the resource);
— CO content (natural mineral water), if relevant to subsequent specified analysis requirements.
2
5.3 Natural waters
Natural waters are waters taken from the natural environment not undergoing to any treatment other
than the addition of reagents for analyte preservation.
Surface waters and groundwater belong to this category. Brackish waters with salinity lower than
30 g/l are incorporated in this category.
Rainwater, which is generally not intended for consumption, are incorporated in this category.
5.4 Waste waters
Waste waters can originate from any combination of household, industrial or commercial activities.
They include collected run-offs and those from any spillage or infiltration from the waste water
collection system, including the contents of storm water tanks or ponds, discharged into collection
systems or into the environment.
NOTE 1 Waste waters can be collected in common systems or in separate systems.
NOTE 2 For the purposes of this document, the definition of waste water also includes untreated sanitary
waters.
NOTE 3 National or local regulations can include lists of substances of concern in relation to sewer discharges.
Annex C gives a list of examples of additional characteristics associated with some sectors of activity.
Some waste waters may have a high salinity.
5.5 Marine waters
Sea water consists of a large number of compounds distributed over the following categories: gases,
particulate matter, colloids, and dissolved elements (see Reference [7]).
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The dissolved elements consist of 92 natural chemical elements, approximately two-thirds of which
are present in ultra-trace amounts and are difficult to detect. Sea water is characterized in that the
[8]
relative proportions of its 11 main constituents are substantially constant (Dittmar's law ) within
1 %. Dittmar's law can thus be used to determine the salinity of sea water by measuring only one of its
components.
The average salinity of sea water is 35 g/kg. It is generally between 30 g/kg (North Atlantic) and 40 g/
kg (Red Sea) but exhibits extreme values in closed or semi-closed seas (6 g/kg in the Baltic Sea, 330 g/
kg in the Dead Sea). The pH of sea water is approximately 8,2.
5.6 Recreational waters
Recreational waters are bathing, swimming pool, thermal bath and spa waters. They may be sourced
from natural waters or waters intended for human consumption and are characterized, in addition to
the influence parameters defined in 5.2, by the potential presence of specific disinfection products and
by-products, and the potential presence of sulfur compounds.
6 Selection of characteristic parameters of a matrix
6.1 General
For the purposes of characterization of the applicability and the performances of an analytical method
to a matrix, the laboratory shall describe the limits of the ranges associated with the characteristic
parameters discussed in this clause.
6.2 All waters
The parameters are those defined in 5.1.
6.3 Waters intended for consumption
In addition to the characteristics listed in 5.1, waters intended for consumption are characterized by:
— their free and total chlorine content;
— the nature and content of disinfection reagents and by-products;
— their CO content, if relevant.
2
Refer to Annex A for more detailed characterization of waters intended for human consumption.
6.4 Natural waters
In addition to the characteristics listed in 5.1, natural waters are characterized by:
— the sampling location, including the sampling depth;
— the identified surrounding anthropic pressures.
In the case of groundwater used as drinking water resources, which are treated in situ, free and total
chlorine content should be verified.
6.5 Waste waters
In addition to the characteristics listed in 5.1, waste waters are characterized by:
— the original activity sector (see Annex C);
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— the connected activity sectors in the case of municipal waste water treatment plants (MWWTP)
discharges.
6.6 Marine waters
In addition to the characteristics listed in 5.1, marine waters are characterized by:
— the sampling location, including sampling depth;
— their salinity.
6.7 Recreational waters
In addition to the characteristics listed in 5.1, recreational waters are characterized by:
— the sampling location;
— the nature and content of disinfection reagents and by products.
7 Available materials
7.1 General
The laboratory shall select study matrices for one or more of the above water types from, in order of
preference:
— reference materials if the matrix is sufficiently characterized;
— supernumerary material from interlaboratory tests if stable and sufficiently characterized;
— material obtained by spiking with the real matrix free from the analytes of interest;
— material obtained by spiking a reasonable dilution of a real matrix, after adjusting the characteristics
modified by the dilution;
— material obtained by spiking of an artificial matrix based on a recipe (see Annex B).
At least three different representative samples of each water type should be studied to provide a
realistic evaluation of performance of the method on the selected water type. Wherever possible, the
method performances shall be characterized on a non-artificial sample.
7.2 Material obtained by reasonable dilution of a real matrix
When the laboratory cannot select a real matrix free from analyte(s) of interest, but it is possible to
select a real matrix containing the analyte(s) of interest at a concentration lower than 10× the limit
of quantification (LOQ) defined for the method under examination, a representative matrix can be
prepared by diluting the low-concentration real matrix, so as to lower the concentration of analyte(s) of
interest to less than the LOQ defined for the method.
The dilution factor, f, shall be lower than 10. For this dilution, a water free from analyte(s) of interest
having a similar composition to the chosen matrix (major elements and influence factors) shall be used.
Before dilution, the selected matrix shall be characterized on the basis of the influence parameters
chosen for the study. After dilution, these parameters shall be readjusted if required using solid state
reagents or stock solutions of solid state reagents so that the value of each influence parameter remains
within the scope defined by the laboratory.
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7.3 Artificial material
Artificial materials can be prepared according to Annex B, after adjusting the influence parameters
selected based on a bibliographic study, and/or on Annex C, within the concentration range defining the
scope of the method.
7.4 Analyte-specific blank values in matrices
For some analytes, such as heavy metals, no analyte-free natural or artificial matrix can be obtained.
After proper justification, the laboratory should study LOQ as follows.
— Determine LOQ on ultrapure water.
MQ
— Calculate LOQ by correcting LOQ using the recovery of the analyte in the intended matric,
water i MQ
i.e. water by using Formula (1):
LOQ
MQ
LOQ = (1)
water i
ρ
water i
where
LOQ is the LOQ of the method for the analyte in water type i;
water i
LOQ is the LOQ of the method for the analyte in ultra pure water;
MQ
is the mean recovery of the method for the analyte in water type i.
ρ
...
SLOVENSKI STANDARD
oSIST-TS ISO/TS 21231:2019
01-maj-2019
Kakovost vode - Karakterizacija analiznih metod - Smernice za izbiro
reprezentativnega matriksa
Water quality - Characterization of analytical methods - Guidelines for the selection of a
representative matrix
Qualité de l'eau - Caractérisation des méthodes d'analyses - Lignes directrices pour la
sélection d'une matrice représentative
Ta slovenski standard je istoveten z: ISO/TS 21231:2019
ICS:
13.060.50 3UHLVNDYDYRGHQDNHPLþQH Examination of water for
VQRYL chemical substances
oSIST-TS ISO/TS 21231:2019 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST-TS ISO/TS 21231:2019
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oSIST-TS ISO/TS 21231:2019
TECHNICAL ISO/TS
SPECIFICATION 21231
First edition
2019-02
Water quality — Characterization of
analytical methods — Guidelines for
the selection of a representative matrix
Reference number
ISO/TS 21231:2019(E)
©
ISO 2019
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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: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
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Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 4
5 Influence parameters . 5
5.1 Common parameters for all matrices . 5
5.2 Water intended for consumption . 6
5.3 Natural waters . 6
5.4 Waste waters . 6
5.5 Marine waters . 6
5.6 Recreational waters . 7
6 Selection of characteristic parameters of a matrix . 7
6.1 General . 7
6.2 All waters . 7
6.3 Waters intended for consumption . 7
6.4 Natural waters . 7
6.5 Waste waters . 7
6.6 Marine waters . 8
6.7 Recreational waters . 8
7 Available materials . 8
7.1 General . 8
7.2 Material obtained by reasonable dilution of a real matrix . 8
7.3 Artificial material . 9
7.4 Analyte-specific blank values in matrices. 9
8 Report . 9
Annex A (informative) Characterization of waters intended for human consumption and
mineral waters .10
Annex B (informative) Examples of preparation of artificial matrices and representative
characteristics .11
Annex C (informative) Occurrence of chemical substances in waste water, by industrial
activity sector .23
Annex D (informative) Leachate .32
Bibliography .33
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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 of 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 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.
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.
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Introduction
This document has been prepared for the validation of analytical methods applied to the water quality
field. It enables a laboratory to determine the characteristics of a material suitable for determination of
the performances of an analytical method itself.
It is not intended to provide an exhaustive inventory of all published recipes, but to propose a selection
of recipes supporting the characterization of the performances of analytical methods used by a
laboratory. For this reason, a restricted number of recipes are proposed. References giving access to
other recipes are available in the Bibliography.
This document includes four recipes for preparing marine waters and five recipes for waste waters
with controlled characteristics.
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TECHNICAL SPECIFICATION ISO/TS 21231:2019(E)
Water quality — Characterization of analytical methods —
Guidelines for the selection of a representative matrix
1 Scope
This document specifies representative materials suitable for the determination of the performance
characteristics, including uncertainty, during the initial assessment of a quantitative method, used in a
laboratory, for physico-chemical water analysis.
This document focuses on five main types of water:
— waters intended for consumption (5.2);
— natural waters (5.3);
— waste waters (5.4);
— marine waters (5.5);
— recreational waters (5.6).
NOTE Other more specific or less common types of water can be incorporated in any of the above types
provided appropriate justifications. The characteristics of the standard matrix are compatible with the
characteristics of the samples handled.
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 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples
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 General vocabulary
3.1.1
matrix
set of constituents of the test sample, except the analyte (3.2.1)
Note 1 to entry: By extension, a matrix defines a group of waters characterized by similar analytical behaviour in
relation to the analytical method used.
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3.1.2
accepted reference value
value that serves as an agreed-upon reference for comparison, and which is derived as:
a) a theoretical or established value, based on scientific principles;
b) an assigned or certified value, based on experimental work of some national or international
organization;
c) a consensus or certified value, based on collaborative experimental work under the auspices of a
scientific or engineering group;
d) when a), b) and c) are not available, the expectation of the (measurable) quantity, i.e. the mean of a
specified population of measurements
Note 1 to entry: In the specific context of this document, the accepted reference value (or conventionally true
value) of the sample is provided according to possibilities by:
— the value from a certified reference material certificate,
— the consensus value obtained from an inter-laboratory comparison,
— the arithmetic mean of the repeated measurement values according to the reference method,
— the target value by adding analyte to a representative matrix of the scope in question.
[SOURCE: ISO 5725-1:1994, 3.5]
3.1.3
reference material
material, sufficiently homogeneous and stable with respect to one or more specified properties, which
has been established to be fit for its intended use in a measurement process
[SOURCE: ISO Guide 35:2017, 3.1]
3.1.4
certified reference material
reference material (3.1.3), accompanied by a certificate, one or more of whose property values are
certified by a procedure which establishes traceability to an accurate realization of the unit in which
the property values are expressed, and for which each certified value is accompanied by an uncertainty
at a stated level of confidence
[SOURCE: ISO/TS 13530:2009, 3.2.7]
3.1.5
assessment procedure
procedure related to the establishment of the specifications for the performance of a new method and/
or experimental verification that a method meets theoretically derived quality criteria
3.2 Terms related to analytical methods
3.2.1
analyte
subject of the analytical method
3.2.2
analytical method
unambiguously written procedure describing all details required to carry out the analysis of the analyte
(3.2.1), namely: scope and field of application, principle and/or reactions, definitions, reagents, apparatus,
analytical procedures, calculations and presentation of results, performance data and test report
[SOURCE: ISO/TS 16489:2006, 3.3]
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3.2.3
quantitative analytical method
analytical method for measuring the quantity of analyte (3.2.1)contained in the test sample
Note 1 to entry: The result can consist of a quantity in a given quantity of test sample.
3.2.4
limit of detection
output signal or value above which it can be affirmed, with a stated level of confidence, for example
95 %, that a sample is different from a blank sample containing no determinand of interest, and which
could be estimated by different means and shall be verified in the intended matrix
[SOURCE: ISO 6107-2:2006, 60, modified — “and which could be estimated by different means and shall
be verified in the intended matrix” has been added.]
3.2.5
limit of quantification
LOQ
lowest value of a determinand that can be determined with an acceptable level of accuracy, which could
be estimated by different means and shall be verified in the intended matrix
Note 1 to entry: For each matrix, this limit is related to the pair [analyte (3.2.1), method].
3.2.6
reasonable dilution
dilution conditions for reducing the concentration of a substance in a matrix without substantially
modifying the intrinsic characteristics of the matrix
3.2.7
matrix blank values
values of a given parameter obtained using a test conducted on a matrix giving rise to a result below the
limit of detection (3.2.4) for the analyte (3.2.1) in question
3.2.8
scope of the analytical method
combination of the various types of matrix and the analyte (3.2.1) concentration range covered, to
which the analytical method applies
Note 1 to entry: In addition to an indication of all the satisfactory performance conditions for each factor, the
scope of the analytical method may also include warnings in respect of known interferences from other analytes,
or inapplicability to some matrices or conditions.
3.3 Terms related to matrix
3.3.1
influence parameter
intrinsic characteristic of the matrix, independent of the analyte (3.2.1) concentration, a variation of
which is liable to modify the analytical result
3.3.2
representative matrix
sample for which all the intrinsic characteristics are characteristic of a type of water or the source of a
group of samples
3.3.3
salinity
mass in grams of solid substances contained in one kilogram of sea water, when the bromide and iodide
ions are replaced by their chloride equivalent, carbonates converted into oxides and all the organic
matter oxidized
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3.3.4
leachate
water which has percolated through tipped refuse or other specified permeable material
Note 1 to entry: See Annex D.
[SOURCE: ISO 6107-7:2006, 23]
4 Principle
The purpose of this document is to specify the concept of a representative matrix and its characteristics
with a view to studying the performance of an analytical method.
For each analyte under test, the scope of an analytical method includes all the matrices under test,
their descriptive parameters, and the concentration ranges of the influence parameters for which the
method is applicable. The laboratory should define its requirements beforehand in respect of the scope
of the analytical method, selecting the materials most in line with requirements.
WARNING — The definition of the scope is entirely dependent on the analyst (the validation or
characterization study manager) and their knowledge acquired while developing the method.
It is sometimes preferable to segment a scope rather than seek to validate an overly general
method. In this case, a validation file should be compiled for each scope.
See Figure 1.
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Figure 1 — Summary flow chart
5 Influence parameters
5.1 Common parameters for all matrices
The following influence parameters are liable to have an impact on analysis procedures. They shall help
classify the types of water on which the laboratory has validated its method or determined performance
characteristics.
— pH;
— ion composition and/or conductivity;
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— salinity;
— dissolved organic carbon (DOC) and/or total organic carbon (TOC);
— colour or turbidity;
— suspended particular matter (SPM) content.
During the validation or characterization study, it is up to the laboratory to:
— define, for its practice, the characteristic ranges associated with each of the above parameters;
— justify, if applicable, the lack of influence thereof on the characterized method;
— complement this list with other characteristic parameters based on the methods and the source of
the samples analysed, using for example Annex A or Annex C.
5.2 Water intended for consumption
Water intended for human and livestock consumption is water considered to be fit for drinking.
Drinking water belongs to this category. It includes groundwater that has been chlorinated in the
resource.
The minimum additional characteristics to be included for this category are:
— disinfectant presence and content (distributed waters or groundwater chlorinated in the resource);
— CO content (natural mineral water), if relevant to subsequent specified analysis requirements.
2
5.3 Natural waters
Natural waters are waters taken from the natural environment not undergoing to any treatment other
than the addition of reagents for analyte preservation.
Surface waters and groundwater belong to this category. Brackish waters with salinity lower than
30 g/l are incorporated in this category.
Rainwater, which is generally not intended for consumption, are incorporated in this category.
5.4 Waste waters
Waste waters can originate from any combination of household, industrial or commercial activities.
They include collected run-offs and those from any spillage or infiltration from the waste water
collection system, including the contents of storm water tanks or ponds, discharged into collection
systems or into the environment.
NOTE 1 Waste waters can be collected in common systems or in separate systems.
NOTE 2 For the purposes of this document, the definition of waste water also includes untreated sanitary
waters.
NOTE 3 National or local regulations can include lists of substances of concern in relation to sewer discharges.
Annex C gives a list of examples of additional characteristics associated with some sectors of activity.
Some waste waters may have a high salinity.
5.5 Marine waters
Sea water consists of a large number of compounds distributed over the following categories: gases,
particulate matter, colloids, and dissolved elements (see Reference [7]).
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The dissolved elements consist of 92 natural chemical elements, approximately two-thirds of which
are present in ultra-trace amounts and are difficult to detect. Sea water is characterized in that the
[8]
relative proportions of its 11 main constituents are substantially constant (Dittmar's law ) within
1 %. Dittmar's law can thus be used to determine the salinity of sea water by measuring only one of its
components.
The average salinity of sea water is 35 g/kg. It is generally between 30 g/kg (North Atlantic) and 40 g/
kg (Red Sea) but exhibits extreme values in closed or semi-closed seas (6 g/kg in the Baltic Sea, 330 g/
kg in the Dead Sea). The pH of sea water is approximately 8,2.
5.6 Recreational waters
Recreational waters are bathing, swimming pool, thermal bath and spa waters. They may be sourced
from natural waters or waters intended for human consumption and are characterized, in addition to
the influence parameters defined in 5.2, by the potential presence of specific disinfection products and
by-products, and the potential presence of sulfur compounds.
6 Selection of characteristic parameters of a matrix
6.1 General
For the purposes of characterization of the applicability and the performances of an analytical method
to a matrix, the laboratory shall describe the limits of the ranges associated with the characteristic
parameters discussed in this clause.
6.2 All waters
The parameters are those defined in 5.1.
6.3 Waters intended for consumption
In addition to the characteristics listed in 5.1, waters intended for consumption are characterized by:
— their free and total chlorine content;
— the nature and content of disinfection reagents and by-products;
— their CO content, if relevant.
2
Refer to Annex A for more detailed characterization of waters intended for human consumption.
6.4 Natural waters
In addition to the characteristics listed in 5.1, natural waters are characterized by:
— the sampling location, including the sampling depth;
— the identified surrounding anthropic pressures.
In the case of groundwater used as drinking water resources, which are treated in situ, free and total
chlorine content should be verified.
6.5 Waste waters
In addition to the characteristics listed in 5.1, waste waters are characterized by:
— the original activity sector (see Annex C);
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— the connected activity sectors in the case of municipal waste water treatment plants (MWWTP)
discharges.
6.6 Marine waters
In addition to the characteristics listed in 5.1, marine waters are characterized by:
— the sampling location, including sampling depth;
— their salinity.
6.7 Recreational waters
In addition to the characteristics listed in 5.1, recreational waters are characterized by:
— the sampling location;
— the nature and content of disinfection reagents and by products.
7 Available materials
7.1 General
The laboratory shall select study matrices for one or more of the above water types from, in order of
preference:
— reference materials if the matrix is sufficiently characterized;
— supernumerary material from interlaboratory tests if stable and sufficiently characterized;
— material obtained by spiking with the real matrix free from the analytes of interest;
— material obtained by spiking a reasonable dilution of a real matrix, after adjusting the characteristics
modified by the dilution;
— material obtained by spiking of an artificial matrix based on a recipe (see Annex B).
At least three different representative samples of each water type should be studied to provide a
realistic evaluation of performance of the method on the selected water type. Wherever possible, the
method performances shall be characterized on a non-artificial sample.
7.2 Material obtained by reasonable dilution of a real matrix
When the laboratory cannot select a real matrix free from analyte(s) of interest, but it is possible to
select a real matrix containing the analyte(s) of interest at a concentration lower than 10× the limit
of quantification (LOQ) defined for the method under examination, a representative matrix can be
prepared by diluting the low-concentration real matrix, so as to lower the concentration of analyte(s) of
interest to less than the LOQ defined for the method.
The dilution factor, f, shall be lower than 10. For this dilution, a water free from analyte(s) of interest
having a similar composition to the chosen matrix (major elements and influence factors) shall be used.
Before dilution, the selected matrix shall be characterized on the basis of the influence parameters
chosen for the study. After dilution, these parameters shall be readjusted if required using solid state
reagents or stock solutions of solid state reagents so that the value of each influence parameter remains
within the scope defined by the laboratory.
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7.3 Artificial material
Artificial materials can be prepared according to Annex B, after adjusting the influence parameters
selected based on a bibliographic study, and/or on Annex C, within the concentration range defining the
scope of the method.
7.4 Analyte-specific blank values in matrices
For some analytes, such as heavy metals, no analyte-free natural or artificial matrix can be obtained.
After proper justification, the laboratory should study LOQ as follows.
— Determine LOQ on ultrapure water.
MQ
— Calculate LOQ by correcting LOQ using the recovery of the analyte in the intended matric,
water i MQ
i.e. water by using Formula (1):
LOQ
MQ
LOQ = (1)
water i
ρ
water i
where
LOQ is the LOQ of the method for the analyte in water type i;
water i
LOQ is the LOQ of the method for the analyte in ultra pure water;
MQ
is the mean recovery of t
...
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