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 2022
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ii
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
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
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
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
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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This document was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 6,
Sampling (general methods).
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iv
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
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
...