ISO TS 5667-25-2022 PDF

Full title and description

Water quality — Sampling — Part 25: Guideline on the validation of the storage time of water samples. This ISO Technical Specification (ISO/TS 5667-25:2022) provides guidance and test-plan methodologies to define and verify how long chemical and physico‑chemical constituents in water samples remain stable under specified preservation and storage conditions prior to analysis; biological and microbiological methods are excluded.

Abstract

ISO/TS 5667-25:2022 describes study designs and operating procedures (for example chronological, isochronous and pseudo‑isochronous test plans), matrix and concentration selection, required analytical‑method performance prerequisites, influence of preservation variables (temperature, light, container material, chemical stabilizers), data handling and statistical evaluation, and the determination and reporting of acceptable storage times (holding times) for water samples intended for chemical and physico‑chemical analyses.

General information

• Status: Published / Confirmed (Technical Specification).
• Publication date: February 2022 (published 22–23 February 2022).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 13.060.45 (Examination of water in general).
• Edition / version: Edition 1, 2022 (ISO/TS 5667-25:2022).
• Number of pages: 50 (approx.; some distributors list 58 pages in national adoption formats).

Scope

This document gives guidance on designing and conducting stability/holding‑time studies to validate the acceptable storage time of water samples for chemical and physico‑chemical analyses under defined preservation conditions (temperature, light exposure, container type, use of stabilizers, etc.). It requires that the analytical method used for the study already has characterized performance (repeatability, intermediate precision, trueness, accuracy and uncertainty). The specification excludes biological and microbiological methods.

Key topics and requirements

• Prerequisite: use of an analytical method with characterized performance (precision, trueness, uncertainty) before stability testing.
• Study designs: chronological, isochronous and pseudo‑isochronous test plans; randomization and batch preparation guidance.
• Selection of representative matrices and concentration levels (surface water, groundwater, drinking water, industrial/residual waters).
• Preservation and storage variables: temperature control, light exposure, container material, chemical stabilizers and other factors influencing stability.
• Data handling and evaluation: graphical representation, statistical assessment, determination of maximum acceptable storage times (holding times/MaxADs) and reporting requirements.
• Annexes and worked examples illustrating application of the test plans and interpretation of results.

Typical use and users

Used by environmental and drinking‑water testing laboratories, accreditation and conformity assessment bodies, regulatory agencies, water utilities and resource managers, environmental consultancies, method developers and quality assurance personnel to establish laboratory‑specific holding times, design stability studies for method validation or regulatory support, and to choose appropriate preservation and storage practices to ensure data quality.

Related standards

ISO/TS 5667-25 is part of the multi‑part ISO 5667 series on water‑quality sampling. Other parts cover general sampling programme design and techniques (Part 1), preservation and handling (Part 3), sampling of rivers and streams (Part 6), sampling of waste waters (Part 10), auditing of sampling (Part 24) and many specialised parts (for example Parts 11, 12, 20, 23, 26, 27, etc.). Users should consult the relevant ISO 5667 parts and national/adopted versions for complementary guidance.

Keywords

water sampling; storage time; holding time; stability study; preservation; isochronous study; chronological study; pseudo‑isochronous; analytical method validation; MaxAD; water quality; ISO 5667.

FAQ

Q: What is this standard?

A: ISO/TS 5667-25:2022 is a Technical Specification in the ISO 5667 series that gives guidelines for validating how long water samples remain suitable for chemical and physico‑chemical analysis under specified storage and preservation conditions.

Q: What does it cover?

A: It covers planning and conducting stability (holding‑time) studies (chronological, isochronous, pseudo‑isochronous), selection of matrices and concentration levels, preservation variables (temperature, light, container, stabilizers), data analysis and the determination and reporting of acceptable storage times. It excludes biological and microbiological methods.

Q: Who typically uses it?

A: Environmental and drinking‑water testing laboratories, regulatory bodies, water utilities, environmental consultants, accreditation assessors and method developers use it to set validated holding times and improve sampling and storage practices.

Q: Is it current or superseded?

A: ISO/TS 5667-25:2022 was published in February 2022 and is the current Technical Specification for this topic; ISO standards and TS documents are subject to periodic review (typically every five years) and national adoptions may have slightly different pagination or publication dates.

Q: Is it part of a series?

A: Yes — it is part of the ISO 5667 series (Water quality — Sampling), which includes multiple parts addressing programme design, specific sampling situations, preservation/handling and quality control of sampling operations.

Q: What are the key keywords?

A: Water sampling, storage time, holding time, stability study, preservation, analytical method validation, isochronous study, MaxAD, ISO 5667.