SIST-TS ISO/TS 5667-25:2023
(Main)Water quality - Sampling - Part 25: Guideline on the validation of the storage time of water samples
Water quality - Sampling - Part 25: Guideline on the validation of the storage time of water samples
The purpose of this document is to describe test plans and different operating methodologies of these test plans to define and verify the acceptable length of stability of a substance in a sample under specified conditions of preservation (temperature, matrix, light, addition of a stabilizer, where appropriate, type of preservation etc.) before starting analytical protocols (chemicals and physico-chemicals analysis). Biological and microbiological methods are excluded.
It is necessary to have an analytical method with performances that have already been characterized (repeatability, intermediate precision, trueness, accuracy and uncertainty) in order to perform the stability study and implement its test plans.
Qualité de l'eau - Échantillonnage - Partie 25: Lignes directrices pour la validation de la durée de conservation des échantillons d'eau
Kakovost vode - Vzorčenje - 25. del: Smernice za validacijo roka uporabnosti vzorcev vode
Namen tega dokumenta je opisati testne načrte in različne metodologije delovanja teh testnih načrtov za opredelitev in preverjanje sprejemljivega trajanja stabilnosti snovi v vzorcu pod določenimi pogoji shranjevanja (temperatura, matrica, svetloba, dodatek stabilizatorja, kjer je to primerno, vrsta shranjevanja itd.) pred začetkom analitskih protokolov (kemijske in fizikalno-kemijske analize). Biološke in mikrobiološke metode so izključene.
Za izvedbo študije stabilnosti in izvajanje načrtov testiranja je treba imeti analitsko metodo z že opredeljenimi testi zmogljivosti (ponovljivost, vmesna natančnost, pravilnost, točnost in negotovost).
General Information
Buy Standard
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TS ISO/TS 5667-25:2023
01-april-2023
Kakovost vode - Vzorčenje - 25. del: Smernice za validacijo roka uporabnosti
vzorcev vode
Water quality - Sampling - Part 25: Guideline on the validation of the storage time of
water samples
Qualité de l'eau - Échantillonnage - Partie 25: Lignes directrices pour la validation de la
durée de conservation des échantillons d'eau
Ta slovenski standard je istoveten z: ISO/TS 5667-25:2022
ICS:
13.060.45 Preiskava vode na splošno Examination of water in
general
SIST-TS ISO/TS 5667-25:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST-TS ISO/TS 5667-25:2023
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SIST-TS ISO/TS 5667-25:2023
TECHNICAL ISO/TS
SPECIFICATION 5667-25
First edition
2022-02
Water quality — Sampling —
Part 25:
Guideline on the validation of the
storage time of water samples
Qualité de l'eau — Échantillonnage —
Partie 25: Lignes directrices pour la validation de la durée de
conservation des échantillons d'eau
Reference number
ISO/TS 5667-25:2022(E)
© ISO 2022
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SIST-TS ISO/TS 5667-25:2023
ISO/TS 5667-25:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
© ISO 2022 – All rights reserved
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SIST-TS ISO/TS 5667-25:2023
ISO/TS 5667-25:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
4 Principle . 5
5 Definition of the scope of the stability study . 6
5.1 Aim of the stability study . 6
5.2 Selection of the maximum acceptable delay before analysis and the acceptance
criteria . 6
5.3 Influence parameters of the maximum acceptable delay before analysis . 7
5.4 Duration of the study . 7
5.5 Concentration levels . 8
5.6 Definition of the matrices and selection of the representative samples . 8
5.7 Guidelines to the stability studies of transformation products . 9
6 Definition of the experimental plan .11
6.1 Determination of the value of the quantity of the material at T and at other times
0
during the study . 11
6.2 Test materials .12
6.2.1 Preparation .12
6.2.2 Characterization of the test materials . 13
6.2.3 MQD Evaluation . 14
6.3 Definition of the test plan . 14
6.3.1 Choice of the type of study . 14
6.3.2 Randomization . 14
7 Performance of the tests .15
7.1 General . 15
7.2 Chronological stability study . 15
7.3 Type 1 pseudo-isochronous stability study . 15
7.4 Type 2 pseudo-isochronous stability study . 16
7.5 Isochronous stability study . 17
8 Graphic representation of the data .17
9 Validation of the data .20
9.1 Initial validation of the study at T . 20
0
9.1.1 Calculation of the value assigned to T (VA ) . 20
0 T0
9.1.2 Verification of the accuracy . 21
9.2 Validation at times different from T . 22
0
10 Using the results . .22
10.1 Graphic view of all the data .22
10.2 Determination of the maximum acceptable delay before analysis by condition .23
10.3 Conclusion of the study . 33
11 Expression of stability .34
Annex A (informative) Measurement process .35
Annex B (informative) Fundamental notions.36
Annex C (informative) Study of stability and influence parameters .42
Annex D (informative) Example of study of atrazine stability in water . 44
Bibliography .50
iii
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SIST-TS ISO/TS 5667-25:2023
ISO/TS 5667-25:2022(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 6,
Sampling (general 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
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SIST-TS ISO/TS 5667-25:2023
ISO/TS 5667-25:2022(E)
Introduction
This document addresses the need for harmonized and reliable data on stability, which is essential
for the expression of recommendations for both normative and regulatory purposes. It describes
a methodological framework that enables laboratories to produce quality data that can be shared
[7]
and even monetized .
It enables laboratories to study the stability of parameters when using the physico-chemical parameters
measurement system: organic micropollutants, inorganic and organometallic micropollutants, nutrients
and macropollutants in aqueous matrices (surface water, ground water, residual urban and industrial
water and drinking water). It covers the sampling, transport and laboratory storage operations.
NOTE This document does not cover solid matrices from aquatic environments (suspended solids,
sediments).
v
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SIST-TS ISO/TS 5667-25:2023
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SIST-TS ISO/TS 5667-25:2023
TECHNICAL SPECIFICATION ISO/TS 5667-25:2022(E)
Water quality — Sampling —
Part 25:
Guideline on the validation of the storage time of water
samples
1 Scope
The purpose of this document is to describe test plans and different operating methodologies
of these test plans to define and verify the acceptable length of stability of a substance in a sample
under specified conditions of preservation (temperature, matrix, light, addition of a stabilizer, where
appropriate, type of preservation etc.) before starting analytical protocols (chemicals and physico-
chemicals analysis). Biological and microbiological methods are excluded.
It is necessary to have an analytical method with performances that have already been characterized
(repeatability, intermediate precision, trueness, accuracy and uncertainty) in order to perform
the stability study and implement its test plans.
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/TS 21231, Water quality — Characterization of analytical methods — Guidelines for the selection of a
representative matrix
3 Terms, definitions and symbols
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
analytical process
detailed description of a measurement according to one or more measurement principles and to one
given measurement method, and including any calculations intended to obtain a measurement result
3.2
batch
definite amount of test material prepared by the laboratory at a given point in
time under supposedly identical conditions
1
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SIST-TS ISO/TS 5667-25:2023
ISO/TS 5667-25:2022(E)
3.3
chronological stability study
study in which individual samples prepared at the same time (i.e., as a batch), under identical conditions,
are measured as time elapses (e.g. one sample immediately, one after three months, the next one after
six months, etc.)
[SOURCE: ISO Guide 35:2017, 8.3.2.1]
3.4
homogeneity
uniformity of a specified property value throughout a defined portion of a reference material (RM)
[2]
Note 1 to entry: Tests for homogeneity are described in ISO Guide 35 .
Note 2 to entry: The “defined portion” may be, for example, an RM batch or a single unit within the batch.
[6]
Note 3 to entry: See also IUPAC Compendium on Analytical Nomenclature .
[SOURCE: ISO Guide 30:2015, 2.1.12]
3.5
influence parameter
intrinsic characteristic of the matrix, independent of the analyte concentration, a variation of which is
liable to modify the analytical result
[SOURCE: ISO/TS 21231:2019, 3.3.1]
3.6
influence parameter of the conditions of preservation
characteristic related to the conditions of storage and preservation of the sample, independent of the
analyte concentration
Note 1 to entry: E.g. container material, storage temperature, influence of light and/or relative humidity.
3.7
integrity
property that the parameter(s) of interest, information or content of the sample container has not been
altered or lost in an unauthorized manner or subject to loss of representativeness
[SOURCE: ISO 5667-3:2018, 3.1]
3.8
intermediate precision condition of measurement
condition of measurement, out of a set of conditions that includes the same measurement procedure,
same location, and replicate measurements on the same or similar objects over an extended period
of time, but may include other conditions involving changes
Note 1 to entry: The changes can include new calibrations, calibrators, operators, and measuring systems.
Note 2 to entry: A specification for the conditions should contain the conditions changed and unchanged,
to the extent practical.
Note 3 to entry: In chemistry, the term “inter-serial precision condition of measurement” is sometimes used
[8]
to designate this concept .
3.9
isochronous stability study
experimental study of “reference” material stability in which units exposed to different storage
conditions and times are measured in a short period of time
[SOURCE: ISO Guide 35:2017, 3.9]
2
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ISO/TS 5667-25:2022(E)
3.10
matrix
all the constituents of the laboratory sample other than the analyte
Note 1 to entry: By extension, a matrix is defined by the analyst as waters characterized by a homogeneous
behaviour with regard to the analytical method used.
[SOURCE: ISO/TS 21231:2019, 3.3.3]
3.11
maximum acceptable delay before analysis
MaxADs
maximum acceptable delay between the end of the sampling process and the start of the analysis
operations, resulting from the stability study, that the laboratory uses to plan the analyses
3.12
maximum acceptable deviation for the stability study
MADs
maximum acceptable deviation relative to the assigned value of the sample at T , used to determine
0
the maximum acceptable delay before analysis
3.13
measurement precision
closeness of agreement between indications or measured quantity values obtained by replicate
measurements on the same or similar objects under specified conditions
Note 1 to entry: Measurement precision is usually expressed numerically by measures of imprecision, such as
standard deviation, variance, or coefficient of variation under the specified conditions of measurement.
Note 2 to entry: The "specified conditions" may be, for example, repeatability conditions of measurement,
intermediate precision conditions of measurement, or reproducibility conditions of measurement
[1]
(see ISO 5725-1:1994 ).
Note 3 to entry: Measurement precision is used to define measurement repeatability, intermediate measurement
precision, and measurement reproducibility.
[8]
Note 4 to entry: Sometimes “measurement precision” is erroneously used to mean measurement accuracy .
3.14
measurement repeatability
measurement precision under a set of repeatability conditions of measurement
[SOURCE: JCGM 200:2012 (VIM), 2.21]
3.15
measurement reproducibility
measurement precision under reproducibility conditions of measurement
Note 1 to entry: I.e., condition of measurement, out of a set of conditions that includes different locations,
operators, measuring systems, and replicate measurements on the same or similar objects.
[SOURCE: JCGM 200:2012 (VIM), 2.25]
3.16
measurement trueness
closeness of agreement between the average of an infinite number of replicates measured quantity
values and a reference quantity value
Note 1 to entry: Measurement trueness is not a quantity and thus cannot be expressed numerically, but measures
[3]
for closeness of agreement are given in ISO 5725-1:1994 .
Note 2 to entry: Measurement trueness is inversely related to systematic measurement error, but is not related to
random measurement error.
3
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SIST-TS ISO/TS 5667-25:2023
ISO/TS 5667-25:2022(E)
Note 3 to entry: “Measurement accuracy” should not be used for ‘measurement trueness’.
[SOURCE: JCGM 200:2012 (VIM), 2.14]
3.17
minimum quantifiable deviation for the stability study (MQDs)
minimum deviation relative to the assigned value of the parameter in the sample at T , which can be
0
unequivocally imputed to the instability
Note 1 to entry: This deviation takes account of the inhomogeneity of the test material and the intrinsic variability
of all the measurement results over time used to determine the maximum acceptable deviations.
Note 2 to entry: The calculation of the minimum quantifiable deviation for the stability study depends on the
type of study (chronological, pseudo-isochronous or isochronous) (6.1.1).
3.18
pseudo-isochronous stability study
stability study in which some of the steps, in particular the preparation, are performed under
intermediate precision conditions, and in which the results of instrumental analyses are acquired
under repeatability conditions
3.19
repeatability condition
condition of measurement, out of a set of conditions that includes the same measurement procedure,
same operators, same measuring system, same operating conditions and same location, and replicate
measurements on the same or similar objects over a short period of time
Note 1 to entry: A condition of measurement is a repeatability condition only with respect to a specified set
of repeatability conditions.
Note 2 to entry: In chemistry, the term “intra-serial precision condition of measurement” is sometimes used
[8]
to designate this concept .
3.20
representative matrix
sample for which all the intrinsic characteristics are characteristics of a type of water or the source of
a group of samples
[SOURCE: ISO/TS 21231:2019, 3.3.2]
3.21
reproducibility condition
condition of measurement, out of a set of conditions that includes different locations, operators,
measuring systems, and replicate measurements on the same or similar objects
Note 1 to entry: The different measuring systems may use different measurement procedures.
[8]
Note 2 to entry: A specification should contain the conditions changed and unchanged, to the extent practical .
3.22
sample preservation
any procedure used to stabilize a sample in such a way that the properties under examination are
maintained stable from the collection step until preparation for analysis
[SOURCE: ISO 5667-3:2018, 3.2]
3.23
sample storage
process and the result of keeping a sample available under predefined conditions, usually for a specified
time interval between collection and further treatment of a sample
Note 1 to entry: Specified time is the maximum time interval [see ISO 5667-3].
4
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SIST-TS ISO/TS 5667-25:2023
ISO/TS 5667-25:2022(E)
3.24
stability
characteristic of an analyte in an aqueous matrix, when stored under specified conditions, to maintain
its property value within specified limits for a specified period from sampling to laboratory operations
3.25
stability interval
interval defined on the basis of the assigned value at T and the maximum acceptable deviation for the
0
stability study
3.26
storage time
period of time between filling of the sample container and further treatment of the sample in the
laboratory, if stored under predefined conditions
Note 1 to entry: Sampling finishes as soon as the sample container has been filled with the sample. Storage time
ends when the sample is taken by the analyst to start sample preparation prior to analysis.
Note 2 to entry: Further treatment is, for most analytes, a solvent extraction or acid destruction. The initial steps
of sample preparation can be steps complementary to the storage conditions for the maintenance of analyte
concentrations.
[SOURCE: ISO 5667-3:2018, 3.4]
4 Principle
The goal is to perform a series of tests, hereafter referred to as the “stability study”, to analyse
the variations in the value of a given parameter, between an initial time and a maximum time, on
samples representative of the scope of application of the measurement method of the parameter. The
conclusions of these tests are used to determine the maximum acceptable delay before analysis (3.11)
under the conditions of the study.
The stability study has six stages:
— Definition of the requirements (analytes, matrices, levels of concentration, storage conditions,
length of storage, maximum acceptable deviation for the stability study (3.12)), see Clause 5;
— Definition of the experiments plan (type of study, number of time intervals and total length
of the study), see Clause 6;
— Performance of the tests, see Clause 7;
— Validation of the data, see Clause 9;
— Using the results (based on a maximum acceptable deviation, 3.12), see Clause 10;
— Expression of the stability in the form of a maximum acceptable delay before analysis (3.11)
and the duration of stability corresponding to the conditions and the criteria (maximum acceptable
deviation for the stability study (3.12)) of the study, see Clause 10.
Since the stability study covers different stages of the data acquisition process according
to the organization of the measurement system, examples of the organization of the measurement
system are given in Annex A for reference.
The laboratory shall take the following factors into consideration:
— The method of determination used: for example, limit of quantification, repeatability, intermediate
precision, accuracy, influence parameters of the matrix (3.10) on the performance of the method;
— The “sample” material of the stability study: for example, homogeneity, physico-chemical properties;
— Suitability of the sample material for use as test material in accordance with storage time (3.26).
5
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SIST-TS ISO/TS 5667-25:2023
ISO/TS 5667-25:2022(E)
— Definition of the influence parameters of the preservation conditions (3.6) assessed as part
of the stability study: for example, time, temperature, addition of stabilizers;
— If studied, command of the storage and transportation conditions;
— Clearly defined acceptability criteria (maximum acceptable deviation, 3.12), with which the results
of the study will be compared.
5 Definition of the scope of the stability study
5.1 Aim of the stability study
Based on the scope of application of the method, the experimental plan shall clearly define the aim of the
stability study by specifying the measured analytes, the matrices (3.10) and the target concentration
levels.
5.2 Selection of the maximum acceptable delay before analysis and the acceptance
criteria
Respecting the maximum acceptable delay before analysis (3.11) may determine the quality of the
results of the analysis more than certain performance data of the measurement methods (bias). This is
the reason why the maximum acceptable delay before analysis shall be established and known before
the routine application of a laboratory analysis method.
The assessment of the results of a stability study with the intension of drawing a conclusion on the
stability, expressed as a maximum acceptable delay before analysis, of a given analyte in a representative
matrix of the scope of application shall be based on the interpretation of the results in perspective of
the requirements of the stability study. A maximum acceptable deviation (3.12) shall be set in order to
come to a conclusion. This maximum acceptable deviation shall be chosen before the start of the study,
because it determines the conditions of performance of the method and the admissibility of the data, in
particular with regard to the measurement method.
There are five ways to determine the maximum acceptable deviation. They are, in order of relevance:
a) The application of a regulatory requirement, if one exists;
b) Twice the repeatability standard deviation for isochronous or pseudo-isochronous type 1 studies
(Annex B), or twice the intermediate precision standard deviation for type 2 pseudo-isochronous
studies (Annex B) or chronological studies; the values of the standard deviation of repeatability
and intermediate precision being the values defined during the characterization of the method.
c) Use of the data from the stability study: dispersion at T of the stability study. See Formula (1):
0
Maximum acceptable deviat
...
TECHNICAL ISO/TS
SPECIFICATION 5667-25
First edition
2022-02
Water quality — Sampling —
Part 25:
Guideline on the validation of the
storage time of water samples
Qualité de l'eau — Échantillonnage —
Partie 25: Lignes directrices pour la validation de la durée de
conservation des échantillons d'eau
Reference number
ISO/TS 5667-25:2022(E)
© ISO 2022
---------------------- Page: 1 ----------------------
ISO/TS 5667-25:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
© ISO 2022 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TS 5667-25:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
4 Principle . 5
5 Definition of the scope of the stability study . 6
5.1 Aim of the stability study . 6
5.2 Selection of the maximum acceptable delay before analysis and the acceptance
criteria . 6
5.3 Influence parameters of the maximum acceptable delay before analysis . 7
5.4 Duration of the study . 7
5.5 Concentration levels . 8
5.6 Definition of the matrices and selection of the representative samples . 8
5.7 Guidelines to the stability studies of transformation products . 9
6 Definition of the experimental plan .11
6.1 Determination of the value of the quantity of the material at T and at other times
0
during the study . 11
6.2 Test materials .12
6.2.1 Preparation .12
6.2.2 Characterization of the test materials . 13
6.2.3 MQD Evaluation . 14
6.3 Definition of the test plan . 14
6.3.1 Choice of the type of study . 14
6.3.2 Randomization . 14
7 Performance of the tests .15
7.1 General . 15
7.2 Chronological stability study . 15
7.3 Type 1 pseudo-isochronous stability study . 15
7.4 Type 2 pseudo-isochronous stability study . 16
7.5 Isochronous stability study . 17
8 Graphic representation of the data .17
9 Validation of the data .20
9.1 Initial validation of the study at T . 20
0
9.1.1 Calculation of the value assigned to T (VA ) . 20
0 T0
9.1.2 Verification of the accuracy . 21
9.2 Validation at times different from T . 22
0
10 Using the results . .22
10.1 Graphic view of all the data .22
10.2 Determination of the maximum acceptable delay before analysis by condition .23
10.3 Conclusion of the study . 33
11 Expression of stability .34
Annex A (informative) Measurement process .35
Annex B (informative) Fundamental notions.36
Annex C (informative) Study of stability and influence parameters .42
Annex D (informative) Example of study of atrazine stability in water . 44
Bibliography .50
iii
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ISO/TS 5667-25:2022(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 6,
Sampling (general 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 2022 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/TS 5667-25:2022(E)
Introduction
This document addresses the need for harmonized and reliable data on stability, which is essential
for the expression of recommendations for both normative and regulatory purposes. It describes
a methodological framework that enables laboratories to produce quality data that can be shared
[7]
and even monetized .
It enables laboratories to study the stability of parameters when using the physico-chemical parameters
measurement system: organic micropollutants, inorganic and organometallic micropollutants, nutrients
and macropollutants in aqueous matrices (surface water, ground water, residual urban and industrial
water and drinking water). It covers the sampling, transport and laboratory storage operations.
NOTE This document does not cover solid matrices from aquatic environments (suspended solids,
sediments).
v
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---------------------- Page: 5 ----------------------
TECHNICAL SPECIFICATION ISO/TS 5667-25:2022(E)
Water quality — Sampling —
Part 25:
Guideline on the validation of the storage time of water
samples
1 Scope
The purpose of this document is to describe test plans and different operating methodologies
of these test plans to define and verify the acceptable length of stability of a substance in a sample
under specified conditions of preservation (temperature, matrix, light, addition of a stabilizer, where
appropriate, type of preservation etc.) before starting analytical protocols (chemicals and physico-
chemicals analysis). Biological and microbiological methods are excluded.
It is necessary to have an analytical method with performances that have already been characterized
(repeatability, intermediate precision, trueness, accuracy and uncertainty) in order to perform
the stability study and implement its test plans.
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/TS 21231, Water quality — Characterization of analytical methods — Guidelines for the selection of a
representative matrix
3 Terms, definitions and symbols
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
analytical process
detailed description of a measurement according to one or more measurement principles and to one
given measurement method, and including any calculations intended to obtain a measurement result
3.2
batch
definite amount of test material prepared by the laboratory at a given point in
time under supposedly identical conditions
1
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3.3
chronological stability study
study in which individual samples prepared at the same time (i.e., as a batch), under identical conditions,
are measured as time elapses (e.g. one sample immediately, one after three months, the next one after
six months, etc.)
[SOURCE: ISO Guide 35:2017, 8.3.2.1]
3.4
homogeneity
uniformity of a specified property value throughout a defined portion of a reference material (RM)
[2]
Note 1 to entry: Tests for homogeneity are described in ISO Guide 35 .
Note 2 to entry: The “defined portion” may be, for example, an RM batch or a single unit within the batch.
[6]
Note 3 to entry: See also IUPAC Compendium on Analytical Nomenclature .
[SOURCE: ISO Guide 30:2015, 2.1.12]
3.5
influence parameter
intrinsic characteristic of the matrix, independent of the analyte concentration, a variation of which is
liable to modify the analytical result
[SOURCE: ISO/TS 21231:2019, 3.3.1]
3.6
influence parameter of the conditions of preservation
characteristic related to the conditions of storage and preservation of the sample, independent of the
analyte concentration
Note 1 to entry: E.g. container material, storage temperature, influence of light and/or relative humidity.
3.7
integrity
property that the parameter(s) of interest, information or content of the sample container has not been
altered or lost in an unauthorized manner or subject to loss of representativeness
[SOURCE: ISO 5667-3:2018, 3.1]
3.8
intermediate precision condition of measurement
condition of measurement, out of a set of conditions that includes the same measurement procedure,
same location, and replicate measurements on the same or similar objects over an extended period
of time, but may include other conditions involving changes
Note 1 to entry: The changes can include new calibrations, calibrators, operators, and measuring systems.
Note 2 to entry: A specification for the conditions should contain the conditions changed and unchanged,
to the extent practical.
Note 3 to entry: In chemistry, the term “inter-serial precision condition of measurement” is sometimes used
[8]
to designate this concept .
3.9
isochronous stability study
experimental study of “reference” material stability in which units exposed to different storage
conditions and times are measured in a short period of time
[SOURCE: ISO Guide 35:2017, 3.9]
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3.10
matrix
all the constituents of the laboratory sample other than the analyte
Note 1 to entry: By extension, a matrix is defined by the analyst as waters characterized by a homogeneous
behaviour with regard to the analytical method used.
[SOURCE: ISO/TS 21231:2019, 3.3.3]
3.11
maximum acceptable delay before analysis
MaxADs
maximum acceptable delay between the end of the sampling process and the start of the analysis
operations, resulting from the stability study, that the laboratory uses to plan the analyses
3.12
maximum acceptable deviation for the stability study
MADs
maximum acceptable deviation relative to the assigned value of the sample at T , used to determine
0
the maximum acceptable delay before analysis
3.13
measurement precision
closeness of agreement between indications or measured quantity values obtained by replicate
measurements on the same or similar objects under specified conditions
Note 1 to entry: Measurement precision is usually expressed numerically by measures of imprecision, such as
standard deviation, variance, or coefficient of variation under the specified conditions of measurement.
Note 2 to entry: The "specified conditions" may be, for example, repeatability conditions of measurement,
intermediate precision conditions of measurement, or reproducibility conditions of measurement
[1]
(see ISO 5725-1:1994 ).
Note 3 to entry: Measurement precision is used to define measurement repeatability, intermediate measurement
precision, and measurement reproducibility.
[8]
Note 4 to entry: Sometimes “measurement precision” is erroneously used to mean measurement accuracy .
3.14
measurement repeatability
measurement precision under a set of repeatability conditions of measurement
[SOURCE: JCGM 200:2012 (VIM), 2.21]
3.15
measurement reproducibility
measurement precision under reproducibility conditions of measurement
Note 1 to entry: I.e., condition of measurement, out of a set of conditions that includes different locations,
operators, measuring systems, and replicate measurements on the same or similar objects.
[SOURCE: JCGM 200:2012 (VIM), 2.25]
3.16
measurement trueness
closeness of agreement between the average of an infinite number of replicates measured quantity
values and a reference quantity value
Note 1 to entry: Measurement trueness is not a quantity and thus cannot be expressed numerically, but measures
[3]
for closeness of agreement are given in ISO 5725-1:1994 .
Note 2 to entry: Measurement trueness is inversely related to systematic measurement error, but is not related to
random measurement error.
3
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Note 3 to entry: “Measurement accuracy” should not be used for ‘measurement trueness’.
[SOURCE: JCGM 200:2012 (VIM), 2.14]
3.17
minimum quantifiable deviation for the stability study (MQDs)
minimum deviation relative to the assigned value of the parameter in the sample at T , which can be
0
unequivocally imputed to the instability
Note 1 to entry: This deviation takes account of the inhomogeneity of the test material and the intrinsic variability
of all the measurement results over time used to determine the maximum acceptable deviations.
Note 2 to entry: The calculation of the minimum quantifiable deviation for the stability study depends on the
type of study (chronological, pseudo-isochronous or isochronous) (6.1.1).
3.18
pseudo-isochronous stability study
stability study in which some of the steps, in particular the preparation, are performed under
intermediate precision conditions, and in which the results of instrumental analyses are acquired
under repeatability conditions
3.19
repeatability condition
condition of measurement, out of a set of conditions that includes the same measurement procedure,
same operators, same measuring system, same operating conditions and same location, and replicate
measurements on the same or similar objects over a short period of time
Note 1 to entry: A condition of measurement is a repeatability condition only with respect to a specified set
of repeatability conditions.
Note 2 to entry: In chemistry, the term “intra-serial precision condition of measurement” is sometimes used
[8]
to designate this concept .
3.20
representative matrix
sample for which all the intrinsic characteristics are characteristics of a type of water or the source of
a group of samples
[SOURCE: ISO/TS 21231:2019, 3.3.2]
3.21
reproducibility condition
condition of measurement, out of a set of conditions that includes different locations, operators,
measuring systems, and replicate measurements on the same or similar objects
Note 1 to entry: The different measuring systems may use different measurement procedures.
[8]
Note 2 to entry: A specification should contain the conditions changed and unchanged, to the extent practical .
3.22
sample preservation
any procedure used to stabilize a sample in such a way that the properties under examination are
maintained stable from the collection step until preparation for analysis
[SOURCE: ISO 5667-3:2018, 3.2]
3.23
sample storage
process and the result of keeping a sample available under predefined conditions, usually for a specified
time interval between collection and further treatment of a sample
Note 1 to entry: Specified time is the maximum time interval [see ISO 5667-3].
4
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3.24
stability
characteristic of an analyte in an aqueous matrix, when stored under specified conditions, to maintain
its property value within specified limits for a specified period from sampling to laboratory operations
3.25
stability interval
interval defined on the basis of the assigned value at T and the maximum acceptable deviation for the
0
stability study
3.26
storage time
period of time between filling of the sample container and further treatment of the sample in the
laboratory, if stored under predefined conditions
Note 1 to entry: Sampling finishes as soon as the sample container has been filled with the sample. Storage time
ends when the sample is taken by the analyst to start sample preparation prior to analysis.
Note 2 to entry: Further treatment is, for most analytes, a solvent extraction or acid destruction. The initial steps
of sample preparation can be steps complementary to the storage conditions for the maintenance of analyte
concentrations.
[SOURCE: ISO 5667-3:2018, 3.4]
4 Principle
The goal is to perform a series of tests, hereafter referred to as the “stability study”, to analyse
the variations in the value of a given parameter, between an initial time and a maximum time, on
samples representative of the scope of application of the measurement method of the parameter. The
conclusions of these tests are used to determine the maximum acceptable delay before analysis (3.11)
under the conditions of the study.
The stability study has six stages:
— Definition of the requirements (analytes, matrices, levels of concentration, storage conditions,
length of storage, maximum acceptable deviation for the stability study (3.12)), see Clause 5;
— Definition of the experiments plan (type of study, number of time intervals and total length
of the study), see Clause 6;
— Performance of the tests, see Clause 7;
— Validation of the data, see Clause 9;
— Using the results (based on a maximum acceptable deviation, 3.12), see Clause 10;
— Expression of the stability in the form of a maximum acceptable delay before analysis (3.11)
and the duration of stability corresponding to the conditions and the criteria (maximum acceptable
deviation for the stability study (3.12)) of the study, see Clause 10.
Since the stability study covers different stages of the data acquisition process according
to the organization of the measurement system, examples of the organization of the measurement
system are given in Annex A for reference.
The laboratory shall take the following factors into consideration:
— The method of determination used: for example, limit of quantification, repeatability, intermediate
precision, accuracy, influence parameters of the matrix (3.10) on the performance of the method;
— The “sample” material of the stability study: for example, homogeneity, physico-chemical properties;
— Suitability of the sample material for use as test material in accordance with storage time (3.26).
5
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— Definition of the influence parameters of the preservation conditions (3.6) assessed as part
of the stability study: for example, time, temperature, addition of stabilizers;
— If studied, command of the storage and transportation conditions;
— Clearly defined acceptability criteria (maximum acceptable deviation, 3.12), with which the results
of the study will be compared.
5 Definition of the scope of the stability study
5.1 Aim of the stability study
Based on the scope of application of the method, the experimental plan shall clearly define the aim of the
stability study by specifying the measured analytes, the matrices (3.10) and the target concentration
levels.
5.2 Selection of the maximum acceptable delay before analysis and the acceptance
criteria
Respecting the maximum acceptable delay before analysis (3.11) may determine the quality of the
results of the analysis more than certain performance data of the measurement methods (bias). This is
the reason why the maximum acceptable delay before analysis shall be established and known before
the routine application of a laboratory analysis method.
The assessment of the results of a stability study with the intension of drawing a conclusion on the
stability, expressed as a maximum acceptable delay before analysis, of a given analyte in a representative
matrix of the scope of application shall be based on the interpretation of the results in perspective of
the requirements of the stability study. A maximum acceptable deviation (3.12) shall be set in order to
come to a conclusion. This maximum acceptable deviation shall be chosen before the start of the study,
because it determines the conditions of performance of the method and the admissibility of the data, in
particular with regard to the measurement method.
There are five ways to determine the maximum acceptable deviation. They are, in order of relevance:
a) The application of a regulatory requirement, if one exists;
b) Twice the repeatability standard deviation for isochronous or pseudo-isochronous type 1 studies
(Annex B), or twice the intermediate precision standard deviation for type 2 pseudo-isochronous
studies (Annex B) or chronological studies; the values of the standard deviation of repeatability
and intermediate precision being the values defined during the characterization of the method.
c) Use of the data from the stability study: dispersion at T of the stability study. See Formula (1):
0
Maximum acceptable deviation = Minimum quantifiable deviatiion (1)
d) The choice of an arbitrary value, determined according to the technical operational implementation
constraints (e.g., the best available method offering a precision of 15 %) or a value from a ring
trial (ISO 5667-3). In this case, the maximum acceptable deviation shall be greater than this value,
e.g., 25 %.
e) A value derived from the temporal operational implementation constraints (e.g., the impossibility
of performing an analysis before a given time due to the minimum transportation time). In this
case, the maximum acceptable delay before analysis is fixed and the maximum acceptable deviation
is based on the observations at the pre-determined time.
EXAMPLE If the temporal constraint is three days, (MaxADs =3 days) the maximum acceptable
deviation is estimated according to the observations (dispersion, for example) at T .
3
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ISO/TS 5667-25:2022(E)
If the minimum quantifiable deviation is greater than the maximum acceptable deviation, it is
impossible to draw any conclusions about the stability. In this case, the laboratory should identify the
...
SLOVENSKI STANDARD
oSIST-TS ISO/TS 5667-25:2022
01-december-2022
Kakovost vode - Vzorčenje -25. del: Smernice za validacijo roka uporabnosti
vzorcev vode
Water quality - Sampling - Part 25: Guideline on the validation of the storage time of
water samples
Qualité de l'eau - Échantillonnage - Partie 25: Lignes directrices pour la validation de la
durée de conservation des échantillons d'eau
Ta slovenski standard je istoveten z: ISO/TS 5667-25:2022
ICS:
13.060.45 Preiskava vode na splošno Examination of water in
general
oSIST-TS ISO/TS 5667-25:2022 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST-TS ISO/TS 5667-25:2022
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oSIST-TS ISO/TS 5667-25:2022
TECHNICAL ISO/TS
SPECIFICATION 5667-25
First edition
2022-02
Water quality — Sampling —
Part 25:
Guideline on the validation of the
storage time of water samples
Qualité de l'eau — Échantillonnage —
Partie 25: Lignes directrices pour la validation de la durée de
conservation des échantillons d'eau
Reference number
ISO/TS 5667-25:2022(E)
© ISO 2022
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oSIST-TS ISO/TS 5667-25:2022
ISO/TS 5667-25:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
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ISO/TS 5667-25:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
4 Principle . 5
5 Definition of the scope of the stability study . 6
5.1 Aim of the stability study . 6
5.2 Selection of the maximum acceptable delay before analysis and the acceptance
criteria . 6
5.3 Influence parameters of the maximum acceptable delay before analysis . 7
5.4 Duration of the study . 7
5.5 Concentration levels . 8
5.6 Definition of the matrices and selection of the representative samples . 8
5.7 Guidelines to the stability studies of transformation products . 9
6 Definition of the experimental plan .11
6.1 Determination of the value of the quantity of the material at T and at other times
0
during the study . 11
6.2 Test materials .12
6.2.1 Preparation .12
6.2.2 Characterization of the test materials . 13
6.2.3 MQD Evaluation . 14
6.3 Definition of the test plan . 14
6.3.1 Choice of the type of study . 14
6.3.2 Randomization . 14
7 Performance of the tests .15
7.1 General . 15
7.2 Chronological stability study . 15
7.3 Type 1 pseudo-isochronous stability study . 15
7.4 Type 2 pseudo-isochronous stability study . 16
7.5 Isochronous stability study . 17
8 Graphic representation of the data .17
9 Validation of the data .20
9.1 Initial validation of the study at T . 20
0
9.1.1 Calculation of the value assigned to T (VA ) . 20
0 T0
9.1.2 Verification of the accuracy . 21
9.2 Validation at times different from T . 22
0
10 Using the results . .22
10.1 Graphic view of all the data .22
10.2 Determination of the maximum acceptable delay before analysis by condition .23
10.3 Conclusion of the study . 33
11 Expression of stability .34
Annex A (informative) Measurement process .35
Annex B (informative) Fundamental notions.36
Annex C (informative) Study of stability and influence parameters .42
Annex D (informative) Example of study of atrazine stability in water . 44
Bibliography .50
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ISO/TS 5667-25:2022(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 6,
Sampling (general 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
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ISO/TS 5667-25:2022(E)
Introduction
This document addresses the need for harmonized and reliable data on stability, which is essential
for the expression of recommendations for both normative and regulatory purposes. It describes
a methodological framework that enables laboratories to produce quality data that can be shared
[7]
and even monetized .
It enables laboratories to study the stability of parameters when using the physico-chemical parameters
measurement system: organic micropollutants, inorganic and organometallic micropollutants, nutrients
and macropollutants in aqueous matrices (surface water, ground water, residual urban and industrial
water and drinking water). It covers the sampling, transport and laboratory storage operations.
NOTE This document does not cover solid matrices from aquatic environments (suspended solids,
sediments).
v
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oSIST-TS ISO/TS 5667-25:2022
TECHNICAL SPECIFICATION ISO/TS 5667-25:2022(E)
Water quality — Sampling —
Part 25:
Guideline on the validation of the storage time of water
samples
1 Scope
The purpose of this document is to describe test plans and different operating methodologies
of these test plans to define and verify the acceptable length of stability of a substance in a sample
under specified conditions of preservation (temperature, matrix, light, addition of a stabilizer, where
appropriate, type of preservation etc.) before starting analytical protocols (chemicals and physico-
chemicals analysis). Biological and microbiological methods are excluded.
It is necessary to have an analytical method with performances that have already been characterized
(repeatability, intermediate precision, trueness, accuracy and uncertainty) in order to perform
the stability study and implement its test plans.
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/TS 21231, Water quality — Characterization of analytical methods — Guidelines for the selection of a
representative matrix
3 Terms, definitions and symbols
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
analytical process
detailed description of a measurement according to one or more measurement principles and to one
given measurement method, and including any calculations intended to obtain a measurement result
3.2
batch
definite amount of test material prepared by the laboratory at a given point in
time under supposedly identical conditions
1
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ISO/TS 5667-25:2022(E)
3.3
chronological stability study
study in which individual samples prepared at the same time (i.e., as a batch), under identical conditions,
are measured as time elapses (e.g. one sample immediately, one after three months, the next one after
six months, etc.)
[SOURCE: ISO Guide 35:2017, 8.3.2.1]
3.4
homogeneity
uniformity of a specified property value throughout a defined portion of a reference material (RM)
[2]
Note 1 to entry: Tests for homogeneity are described in ISO Guide 35 .
Note 2 to entry: The “defined portion” may be, for example, an RM batch or a single unit within the batch.
[6]
Note 3 to entry: See also IUPAC Compendium on Analytical Nomenclature .
[SOURCE: ISO Guide 30:2015, 2.1.12]
3.5
influence parameter
intrinsic characteristic of the matrix, independent of the analyte concentration, a variation of which is
liable to modify the analytical result
[SOURCE: ISO/TS 21231:2019, 3.3.1]
3.6
influence parameter of the conditions of preservation
characteristic related to the conditions of storage and preservation of the sample, independent of the
analyte concentration
Note 1 to entry: E.g. container material, storage temperature, influence of light and/or relative humidity.
3.7
integrity
property that the parameter(s) of interest, information or content of the sample container has not been
altered or lost in an unauthorized manner or subject to loss of representativeness
[SOURCE: ISO 5667-3:2018, 3.1]
3.8
intermediate precision condition of measurement
condition of measurement, out of a set of conditions that includes the same measurement procedure,
same location, and replicate measurements on the same or similar objects over an extended period
of time, but may include other conditions involving changes
Note 1 to entry: The changes can include new calibrations, calibrators, operators, and measuring systems.
Note 2 to entry: A specification for the conditions should contain the conditions changed and unchanged,
to the extent practical.
Note 3 to entry: In chemistry, the term “inter-serial precision condition of measurement” is sometimes used
[8]
to designate this concept .
3.9
isochronous stability study
experimental study of “reference” material stability in which units exposed to different storage
conditions and times are measured in a short period of time
[SOURCE: ISO Guide 35:2017, 3.9]
2
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3.10
matrix
all the constituents of the laboratory sample other than the analyte
Note 1 to entry: By extension, a matrix is defined by the analyst as waters characterized by a homogeneous
behaviour with regard to the analytical method used.
[SOURCE: ISO/TS 21231:2019, 3.3.3]
3.11
maximum acceptable delay before analysis
MaxADs
maximum acceptable delay between the end of the sampling process and the start of the analysis
operations, resulting from the stability study, that the laboratory uses to plan the analyses
3.12
maximum acceptable deviation for the stability study
MADs
maximum acceptable deviation relative to the assigned value of the sample at T , used to determine
0
the maximum acceptable delay before analysis
3.13
measurement precision
closeness of agreement between indications or measured quantity values obtained by replicate
measurements on the same or similar objects under specified conditions
Note 1 to entry: Measurement precision is usually expressed numerically by measures of imprecision, such as
standard deviation, variance, or coefficient of variation under the specified conditions of measurement.
Note 2 to entry: The "specified conditions" may be, for example, repeatability conditions of measurement,
intermediate precision conditions of measurement, or reproducibility conditions of measurement
[1]
(see ISO 5725-1:1994 ).
Note 3 to entry: Measurement precision is used to define measurement repeatability, intermediate measurement
precision, and measurement reproducibility.
[8]
Note 4 to entry: Sometimes “measurement precision” is erroneously used to mean measurement accuracy .
3.14
measurement repeatability
measurement precision under a set of repeatability conditions of measurement
[SOURCE: JCGM 200:2012 (VIM), 2.21]
3.15
measurement reproducibility
measurement precision under reproducibility conditions of measurement
Note 1 to entry: I.e., condition of measurement, out of a set of conditions that includes different locations,
operators, measuring systems, and replicate measurements on the same or similar objects.
[SOURCE: JCGM 200:2012 (VIM), 2.25]
3.16
measurement trueness
closeness of agreement between the average of an infinite number of replicates measured quantity
values and a reference quantity value
Note 1 to entry: Measurement trueness is not a quantity and thus cannot be expressed numerically, but measures
[3]
for closeness of agreement are given in ISO 5725-1:1994 .
Note 2 to entry: Measurement trueness is inversely related to systematic measurement error, but is not related to
random measurement error.
3
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ISO/TS 5667-25:2022(E)
Note 3 to entry: “Measurement accuracy” should not be used for ‘measurement trueness’.
[SOURCE: JCGM 200:2012 (VIM), 2.14]
3.17
minimum quantifiable deviation for the stability study (MQDs)
minimum deviation relative to the assigned value of the parameter in the sample at T , which can be
0
unequivocally imputed to the instability
Note 1 to entry: This deviation takes account of the inhomogeneity of the test material and the intrinsic variability
of all the measurement results over time used to determine the maximum acceptable deviations.
Note 2 to entry: The calculation of the minimum quantifiable deviation for the stability study depends on the
type of study (chronological, pseudo-isochronous or isochronous) (6.1.1).
3.18
pseudo-isochronous stability study
stability study in which some of the steps, in particular the preparation, are performed under
intermediate precision conditions, and in which the results of instrumental analyses are acquired
under repeatability conditions
3.19
repeatability condition
condition of measurement, out of a set of conditions that includes the same measurement procedure,
same operators, same measuring system, same operating conditions and same location, and replicate
measurements on the same or similar objects over a short period of time
Note 1 to entry: A condition of measurement is a repeatability condition only with respect to a specified set
of repeatability conditions.
Note 2 to entry: In chemistry, the term “intra-serial precision condition of measurement” is sometimes used
[8]
to designate this concept .
3.20
representative matrix
sample for which all the intrinsic characteristics are characteristics of a type of water or the source of
a group of samples
[SOURCE: ISO/TS 21231:2019, 3.3.2]
3.21
reproducibility condition
condition of measurement, out of a set of conditions that includes different locations, operators,
measuring systems, and replicate measurements on the same or similar objects
Note 1 to entry: The different measuring systems may use different measurement procedures.
[8]
Note 2 to entry: A specification should contain the conditions changed and unchanged, to the extent practical .
3.22
sample preservation
any procedure used to stabilize a sample in such a way that the properties under examination are
maintained stable from the collection step until preparation for analysis
[SOURCE: ISO 5667-3:2018, 3.2]
3.23
sample storage
process and the result of keeping a sample available under predefined conditions, usually for a specified
time interval between collection and further treatment of a sample
Note 1 to entry: Specified time is the maximum time interval [see ISO 5667-3].
4
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oSIST-TS ISO/TS 5667-25:2022
ISO/TS 5667-25:2022(E)
3.24
stability
characteristic of an analyte in an aqueous matrix, when stored under specified conditions, to maintain
its property value within specified limits for a specified period from sampling to laboratory operations
3.25
stability interval
interval defined on the basis of the assigned value at T and the maximum acceptable deviation for the
0
stability study
3.26
storage time
period of time between filling of the sample container and further treatment of the sample in the
laboratory, if stored under predefined conditions
Note 1 to entry: Sampling finishes as soon as the sample container has been filled with the sample. Storage time
ends when the sample is taken by the analyst to start sample preparation prior to analysis.
Note 2 to entry: Further treatment is, for most analytes, a solvent extraction or acid destruction. The initial steps
of sample preparation can be steps complementary to the storage conditions for the maintenance of analyte
concentrations.
[SOURCE: ISO 5667-3:2018, 3.4]
4 Principle
The goal is to perform a series of tests, hereafter referred to as the “stability study”, to analyse
the variations in the value of a given parameter, between an initial time and a maximum time, on
samples representative of the scope of application of the measurement method of the parameter. The
conclusions of these tests are used to determine the maximum acceptable delay before analysis (3.11)
under the conditions of the study.
The stability study has six stages:
— Definition of the requirements (analytes, matrices, levels of concentration, storage conditions,
length of storage, maximum acceptable deviation for the stability study (3.12)), see Clause 5;
— Definition of the experiments plan (type of study, number of time intervals and total length
of the study), see Clause 6;
— Performance of the tests, see Clause 7;
— Validation of the data, see Clause 9;
— Using the results (based on a maximum acceptable deviation, 3.12), see Clause 10;
— Expression of the stability in the form of a maximum acceptable delay before analysis (3.11)
and the duration of stability corresponding to the conditions and the criteria (maximum acceptable
deviation for the stability study (3.12)) of the study, see Clause 10.
Since the stability study covers different stages of the data acquisition process according
to the organization of the measurement system, examples of the organization of the measurement
system are given in Annex A for reference.
The laboratory shall take the following factors into consideration:
— The method of determination used: for example, limit of quantification, repeatability, intermediate
precision, accuracy, influence parameters of the matrix (3.10) on the performance of the method;
— The “sample” material of the stability study: for example, homogeneity, physico-chemical properties;
— Suitability of the sample material for use as test material in accordance with storage time (3.26).
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oSIST-TS ISO/TS 5667-25:2022
ISO/TS 5667-25:2022(E)
— Definition of the influence parameters of the preservation conditions (3.6) assessed as part
of the stability study: for example, time, temperature, addition of stabilizers;
— If studied, command of the storage and transportation conditions;
— Clearly defined acceptability criteria (maximum acceptable deviation, 3.12), with which the results
of the study will be compared.
5 Definition of the scope of the stability study
5.1 Aim of the stability study
Based on the scope of application of the method, the experimental plan shall clearly define the aim of the
stability study by specifying the measured analytes, the matrices (3.10) and the target concentration
levels.
5.2 Selection of the maximum acceptable delay before analysis and the acceptance
criteria
Respecting the maximum acceptable delay before analysis (3.11) may determine the quality of the
results of the analysis more than certain performance data of the measurement methods (bias). This is
the reason why the maximum acceptable delay before analysis shall be established and known before
the routine application of a laboratory analysis method.
The assessment of the results of a stability study with the intension of drawing a conclusion on the
stability, expressed as a maximum acceptable delay before analysis, of a given analyte in a representative
matrix of the scope of application shall be based on the interpretation of the results in perspective of
the requirements of the stability study. A maximum acceptable deviation (3.12) shall be set in order to
come to a conclusion. This maximum acceptable deviation shall be chosen before the start of the study,
because it determines the conditions of performance of the method and the admissibility of the data, in
particular with regard to the measurement method.
There are five ways to determine the maximum acceptable deviation. They are, in order of relevance:
a) The application of a regulatory requirement, if one exists;
b) Twice the repeatability standard deviation for isochronous or pseudo-isochronous type 1 studies
(Annex B), or twice the intermediate precision standard deviation for type 2 pseudo-isochronous
studies (Annex B) or chronological studies; the values of the standard deviation of repeatability
and intermediate precision being the values defined during the characterization of the method.
c) Use of the data from the stability study: dispersion at T of the stability study. See Formula (1):
0
Maximum
...
TECHNICAL ISO/TS
SPECIFICATION 5667-25
First edition
Water quality — Sampling —
Part 25:
Guideline on the validation of the
preservation time of water samples
Qualité de l'eau — Échantillonnage —
Partie 25: Lignes directrices pour la validation de la durée de
conservation des échantillons d'eau
PROOF/ÉPREUVE
Reference number
ISO/TS 5667-25:2021(E)
© ISO 2021
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ISO/TS 5667-25:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
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Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
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ISO/TS 5667-25:2021(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
4 Principle . 5
5 Definition of the scope of the stability study . 6
5.1 Aim of the stability study . 6
5.2 Selection of the maximum acceptable delay before analysis and the acceptance
criteria . 6
5.3 Influence parameters of the maximum acceptable delay before analysis . 7
5.4 Duration of the study . 7
5.5 Concentration levels . 8
5.6 Definition of the matrices and selection of the representative samples . 8
5.7 Guidelines to the stability studies of transformation products . 9
6 Definition of the experimental plan .10
6.1 Determination of the value of the quantity of the material at T and at other times
0
during the study . 10
6.2 Test materials .12
6.2.1 Preparation .12
6.2.2 Characterization of the test materials . 13
6.2.3 MQD Evaluation . 13
6.3 Definition of the test plan .13
6.3.1 Choice of the type of study . 13
6.3.2 Randomization . 13
7 Performance of the tests .14
7.1 General . 14
7.2 Chronological stability study . 14
7.3 Type 1 pseudo-isochronous stability study . 15
7.4 Type 2 pseudo-isochronous stability study . 15
7.5 Isochronous stability study . 16
8 Graphic representation of the data .16
9 Validation of the data .19
9.1 Initial validation of the study at T . 19
0
9.1.1 Calculation of the value assigned to T (VA ) . 19
0 T0
9.1.2 Verification of the accuracy . 20
9.2 Validation at times different from T . 21
0
10 Using the results . .21
10.1 Graphic view of all the data . 21
10.2 Determination of the maximum acceptable delay before analysis by condition .22
10.3 Conclusion of the study . 32
11 Expression of stability .33
Annex A (informative) Measurement process .34
Annex B (informative) Fundamental notions.35
Annex C (informative) Study of stability and influence parameters .41
Annex D (informative) Example of study of atrazine stability in water .43
Bibliography .49
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ISO/TS 5667-25:2021(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 6,
Sampling (general 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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ISO/TS 5667-25:2021(E)
Introduction
This document addresses the need for harmonized and reliable data on stability, which is essential
for the expression of recommendations for both normative and regulatory purposes. It describes
a methodological framework that enables laboratories to produce quality data that can be shared
[7]
and even monetized .
It enables laboratories to study the stability of parameters when using the physico-chemical parameters
measurement system: organic micropollutants, inorganic and organometallic micropollutants, nutrients
and macropollutants in aqueous matrices (surface water, ground water, residual urban and industrial
water and drinking water). It covers the sampling, transport and laboratory storage operations.
NOTE This document does not cover solid matrices from aquatic environments (suspended solids,
sediments).
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TECHNICAL SPECIFICATION ISO/TS 5667-25:2021(E)
Water quality — Sampling —
Part 25:
Guideline on the validation of the preservation time of
water samples
1 Scope
The purpose of this document is to describe test plans and different operating methodologies
of these test plans to define and verify the acceptable length of stability of a substance in a sample
under specified conditions of preservation (temperature, matrix, light, addition of a stabilizer, where
appropriate, type of preservation etc.) before starting analytical protocols (chemicals and physico-
chemicals analysis). Biological and microbiological methods are excluded.
It is necessary to have an analytical method with performances that have already been characterized
(repeatability, intermediate precision, trueness, accuracy and uncertainty) in order to perform
the stability study and implement its test plans.
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/TS 21231, Water quality — Characterization of analytical methods — Guidelines for the selection of a
representative matrix
3 Terms, definitions and symbols
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 https:// www .electropedia .org/
For the purposes of this document, the following terms and definitions apply.
3.1
analytical process
detailed description of a measurement according to one or more measurement principles and to one
given measurement method, and including any calculations intended to obtain a measurement result
3.2
batch (production, material)
definite amount of test material prepared by the laboratory at a given point in time under supposedly
identical conditions
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ISO/TS 5667-25:2021(E)
3.3
chronological stability study
study in which individual samples prepared at the same time (i.e., as a batch), under identical conditions,
are measured as time elapses (e.g. one sample immediately, one after three months, the next one after
six months, etc.)
[SOURCE: ISO Guide 35:2017, 8.3.2.1]
3.4
homogeneity
uniformity of a specified property value throughout a defined portion of a reference material (RM)
[2]
Note 1 to entry: Tests for homogeneity are described in ISO Guide 35 .
Note 2 to entry: The “defined portion” may be, for example, an RM batch or a single unit within the batch.
[6]
Note 3 to entry: See also IUPAC Compendium on Analytical Nomenclature .
[SOURCE: ISO Guide 30:2015, 2.1.12]
3.5
influence parameter
intrinsic characteristic of the matrix, independent of the analyte concentration, a variation of which is
liable to modify the analytical result
[SOURCE: ISO/TS 21231:2019, 3.3.1]
3.6
influence parameter of the conditions of preservation
characteristic related to the conditions of storage and preservation of the sample, independent of the
analyte concentration
Note 1 to entry: E.g. container material, storage temperature, influence of light and/or relative humidity.
3.7
integrity
property that the parameter(s) of interest, information or content of the sample container has not been
altered or lost in an unauthorized manner or subject to loss of representativeness
[SOURCE: ISO 5667-3:2018, 3.1]
3.8
intermediate precision condition of measurement
condition of measurement, out of a set of conditions that includes the same measurement procedure,
same location, and replicate measurements on the same or similar objects over an extended period
of time, but may include other conditions involving changes
Note 1 to entry: The changes can include new calibrations, calibrators, operators, and measuring systems.
Note 2 to entry: A specification for the conditions should contain the conditions changed and unchanged,
to the extent practical.
Note 3 to entry: In chemistry, the term “inter-serial precision condition of measurement” is sometimes used
[8]
to designate this concept .
3.9
isochronous stability study
experimental study of “reference” material stability in which units exposed to different storage
conditions and times are measured in a short period of time
[SOURCE: ISO Guide 35:2017, 3.9]
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ISO/TS 5667-25:2021(E)
3.10
matrix
all the constituents of the laboratory sample other than the analyte
Note 1 to entry: By extension, a matrix is defined by the analyst as waters characterized by a homogeneous
behaviour with regard to the analytical method used.
[SOURCE: ISO/TS 21231:2019, 3.3.3]
3.11
maximum acceptable delay before analysis (MaxADs)
maximum acceptable delay between the end of the sampling process and the start of the analysis
operations, resulting from the stability study, that the laboratory uses to plan the analyses
3.12
maximum acceptable deviation for the stability study (MADs)
maximum acceptable deviation relative to the assigned value of the sample at T , used to determine
0
the maximum acceptable delay before analysis
3.13
measurement precision
closeness of agreement between indications or measured quantity values obtained by replicate
measurements on the same or similar objects under specified conditions
Note 1 to entry: Measurement precision is usually expressed numerically by measures of imprecision, such as
standard deviation, variance, or coefficient of variation under the specified conditions of measurement.
Note 2 to entry: The "specified conditions" may be, for example, repeatability conditions of measurement,
intermediate precision conditions of measurement, or reproducibility conditions of measurement
[1]
(see ISO 5725-1:1994 ).
Note 3 to entry: Measurement precision is used to define measurement repeatability, intermediate measurement
precision, and measurement reproducibility.
[8]
Note 4 to entry: Sometimes “measurement precision” is erroneously used to mean measurement accuracy .
3.14
measurement repeatability
measurement precision under a set of repeatability conditions of measurement
[SOURCE: JCGM 200:2012 (VIM), 2.21]
3.15
measurement reproducibility
measurement precision under reproducibility conditions of measurement
Note 1 to entry: I.e., condition of measurement, out of a set of conditions that includes different locations,
operators, measuring systems, and replicate measurements on the same or similar objects.
[SOURCE: JCGM 200:2012 (VIM), 2.25]
3.16
measurement trueness
closeness of agreement between the average of an infinite number of replicates measured quantity
values and a reference quantity value
Note 1 to entry: Measurement trueness is not a quantity and thus cannot be expressed numerically, but measures
[3]
for closeness of agreement are given in ISO 5725-1:1994 .
Note 2 to entry: Measurement trueness is inversely related to systematic measurement error, but is not related to
random measurement error.
Note 3 to entry: “Measurement accuracy” should not be used for ‘measurement trueness’.
3
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ISO/TS 5667-25:2021(E)
[SOURCE: JCGM 200:2012 (VIM), 2.14]
3.17
minimum quantifiable deviation for the stability study (MQDs)
minimum deviation relative to the assigned value of the parameter in the sample at T , which can be
0
unequivocally imputed to the instability
Note 1 to entry: This deviation takes account of the inhomogeneity of the test material and the intrinsic variability
of all the measurement results over time used to determine the maximum acceptable deviations.
Note 2 to entry: The calculation of the minimum quantifiable deviation for the stability study depends on the
type of study (chronological, pseudo-isochronous or isochronous) (6.1.1).
3.18
pseudo-isochronous stability study
stability study in which some of the steps, in particular the preparation, are performed under
intermediate precision conditions, and in which the results of instrumental analyses are acquired
under repeatability conditions
3.19
repeatability condition
condition of measurement, out of a set of conditions that includes the same measurement procedure,
same operators, same measuring system, same operating conditions and same location, and replicate
measurements on the same or similar objects over a short period of time
Note 1 to entry: A condition of measurement is a repeatability condition only with respect to a specified set
of repeatability conditions.
Note 2 to entry: In chemistry, the term “intra-serial precision condition of measurement” is sometimes used
[8]
to designate this concept .
3.20
representative matrix
sample for which all the intrinsic characteristics are characteristics of a type of water or the source of
a group of samples
[SOURCE: ISO/TS 21231:2019, 3.3.2]
3.21
reproducibility condition
condition of measurement, out of a set of conditions that includes different locations, operators,
measuring systems, and replicate measurements on the same or similar objects
Note 1 to entry: The different measuring systems may use different measurement procedures.
[8]
Note 2 to entry: A specification should contain the conditions changed and unchanged, to the extent practical .
3.22
sample preservation
any procedure used to stabilize a sample in such a way that the properties under examination are
maintained stable from the collection step until preparation for analysis
[SOURCE: ISO 5667-3:2018, 3.2]
3.23
sample storage
process and the result of keeping a sample available under predefined conditions, usually for a specified
time interval between collection and further treatment of a sample
Note 1 to entry: Specified time is the maximum time interval [see ISO 5667-3].
4
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ISO/TS 5667-25:2021(E)
3.24
stability
characteristic of an analyte in an aqueous matrix, when stored under specified conditions, to maintain
its property value within specified limits for a specified period from sampling to laboratory operations
3.25
stability interval
interval defined on the basis of the assigned value at T and the maximum acceptable deviation for the
0
stability study
3.26
storage time
period of time between filling of the sample container and further treatment of the sample in the
laboratory, if stored under predefined conditions
Note 1 to entry: Sampling finishes as soon as the sample container has been filled with the sample. Storage time
ends when the sample is taken by the analyst to start sample preparation prior to analysis.
Note 2 to entry: Further treatment is, for most analytes, a solvent extraction or acid destruction. The initial steps
of sample preparation can be steps complementary to the storage conditions for the maintenance of analyte
concentrations.
[SOURCE: ISO 5667-3:2018, 3.4]
4 Principle
The goal is to perform a series of tests, hereafter referred to as the “stability study”, to analyse
the variations in the value of a given parameter, between an initial time and a maximum time, on
samples representative of the scope of application of the measurement method of the parameter. The
conclusions of these tests are used to determine the maximum acceptable delay before analysis (3.11)
under the conditions of the study.
The stability study has six stages:
— Definition of the requirements (analytes, matrices, levels of concentration, storage conditions,
length of storage, maximum acceptable deviation for the stability study (3.12)), see Clause 5;
— Definition of the experiments plan (type of study, number of time intervals and total length
of the study), see Clause 6;
— Performance of the tests, see Clause 7;
— Validation of the data, see Clause 9;
— Using the results (based on a maximum acceptable deviation, 3.12), see Clause 10;
— Expression of the stability in the form of a maximum acceptable delay before analysis (3.11)
and the duration of stability corresponding to the conditions and the criteria (maximum acceptable
deviation for the stability study (3.12)) of the study, see Clause 10.
Since the stability study covers different stages of the data acquisition process according
to the organization of the measurement system, examples of the organization of the measurement
system are given in Annex A for reference.
The laboratory shall take the following factors into consideration:
— The method of determination used: for example, limit of quantification, repeatability, intermediate
precision, accuracy, influence parameters of the matrix (3.10) on the performance of the method;
— The “sample” material of the stability study: for example, homogeneity, physico-chemical properties;
— Suitability of the sample material for use as test material in accordance with storage time (3.26).
5
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ISO/TS 5667-25:2021(E)
— Definition of the influence parameters of the preservation conditions (3.6) assessed as part
of the stability study: for example, time, temperature, addition of stabilizers;
— If studied, command of the storage and transportation conditions;
— Clearly defined acceptability criteria (maximum acceptable deviation, 3.12), with which the results
of the study will be compared.
5 Definition of the scope of the stability study
5.1 Aim of the stability study
Based on the scope of application of the method, the experimental plan shall clearly define the aim of the
stability study by specifying the measured analytes, the matrices (3.10) and the target concentration
levels.
5.2 Selection of the maximum acceptable delay before analysis and the acceptance
criteria
Respecting the maximum acceptable delay before analysis (3.11) may determine the quality of the
results of the analysis more than certain performance data of the measurement methods (bias). This is
the reason why the maximum acceptable delay before analysis shall be established and known before
the routine application of a laboratory analysis method.
The assessment of the results of a stability study with the intension of drawing a conclusion on the
stability, expressed as a maximum acceptable delay before analysis, of a given analyte in a representative
matrix of the scope of application shall be based on the interpretation of the results in perspective of
the requirements of the stability study. A maximum acceptable deviation (3.12) shall be set in order to
come to a conclusion. This maximum acceptable deviation shall be chosen before the start of the study,
because it determines the conditions of performance of the method and the admissibility of the data, in
particular with regard to the measurement method.
There are five ways to determine the maximum acceptable deviation. They are, in order of relevance:
a) The application of a regulatory requirement, if one exists;
b) Twice the repeatability standard deviation for isochronous or pseudo-isochronous type 1 studies
(Annex B), or twice the intermediate precision standard deviation for type 2 pseudo-isochronous
studies (Annex B) or chronological studies; the values of the standard deviation of repeatability
and intermediate precision being the values defined during the characterization of the method.
c) Use of the data from the stability study: dispersion at T of the stability study. See Formula (1):
0
Maximum acceptable deviation = Minimum quantifiable deviatiion (1)
d) The choice of an arbitrary value, determined according to the technical operational implementation
constraints (e.g., the best available method offering a precision of 15 %) or a value from a CIL
(ISO 5667-3). In this case, the maximum acceptable deviation shall be greater than this value,
e.g., 25 %.
e) A value derived from the temporal operational implementation constraints (e.g., the impossibility
of performing an analysis before a given time due to the minimum transportation time). In this
case, the maximum acceptable delay before analysis is fixed and the maximum acceptable deviation
is based on the observations at the pre-determined time.
EXAMPLE If the temporal constraint is three days, (MaxADs =3 days) the maximum acceptable
deviation is estimated according to the observations (dispersion, for example) at T .
3
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ISO/TS 5667-25:2021(E)
If the minimum quantifiable deviation is greater than
...
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