Setting and Using Target Uncertainty in Chemical Measurement

Contents

The Eurachem/CITAC Measurement uncertainty and traceability working group has prepared this Guide to as part of a sequence of guidelines that aims at promoting the production of measurement results that are traceable to an adequate reference and are reported with reliable and sufficiently low uncertainty for the intended use of the measurement. These features are essential for the adequate interpretation of the measurement result which is discussed in the Eurachem/CITAC guide, ‘Use of uncertainty information in compliance assessment’.

This document discusses how to set a maximum admissible uncertainty, defined in the third edition of the International Vocabulary of Metrology as the “target uncertainty”, to check whether measurement quality quantified by the measurement uncertainty is fit for the intended purpose.

This guideline is applicable to analytical fields where the target uncertainty is not set by the regulator or the client, or where a minimum difference of the studied parameter in the same or different items must be detected in R&D work. This guide discusses how to set the target uncertainty for process development and for applied or fundamental research using information about the smallest difference or system trend that must be distinguished in a reliable way.

This guideline can also be useful for authorities and stakeholders that feel the need to define or upgrade criteria for measurements quality. The setting of target values for the so called conventional performance characteristics (precision, trueness, etc.) can miss the control of important uncertainty components included in sound uncertainty evaluations.

The document fills a gap in the current list of guidance for measurements in chemistry and can contribute to ensuring measurements play their role in the management of socio-economic interests and in the technological and scientific developments of society.

Availability

You may download the Guide from this website at no cost. 

NB: See also "Comments and errata" below.

• Download the guide in EnglishNote: Editorial corrections are available for this edition (below).  (pdf, 1.071 MB, published 2015-09-28)
• Download the guide in Portuguese (pdf, 1.3 MB, published 2020-12-19)
• Download the guide in Farsi (pdf, 1.3 MB, published 2016-06-28)
• Download the guide in Spanish (pdf, 783 kB, published 2019-07-24)

Translations

Translation into other languages is permitted for members of Eurachem. Other offers of translation should be directed to the Eurachem Secretariat for permission. The Eurachem policy on maintenance and development of Eurachem guidance, available on the Policies page, gives further information on translation.

Recommended citation

This publication should be cited* as: “R. Bettencourt da Silva, A. Williams (Eds), Eurachem/CITAC Guide: Setting and Using Target Uncertainty in Chemical Measurement, (1st ed. 2015). ISBN: 978-989-98723-7-0. Available from www.eurachem.org.”
*Subject to journal requirements

Approval and publication

This guide was approved for publication** by the Eurachem GA in May 2015 and first published on this website on 2015-09-28.
**Subject to minor comments

Comments and errata

Since publication of the Guide in 2015, a number of minor typographical issues have been identified. Although not sufficient to justify revision and re-issue of the complete Guide and translations, the Measurement Uncertainty and Traceability WG have prepared a list of comments and corrections for reader information. These are likely to be implemented in future editions.

• View all comments and errata.

The Fitness for Purpose of Analytical Methods (2025)

Full title

The Fitness for Purpose of Analytical Methods: A Laboratory Guide to Method Validation and Related Topics: Third edition (2025)

Quick links:

• Overview of the guide
• Downloads
• Citing the guide
• Supplementary guidance on method validation topics
• Previous versions

Introduction

This guide was first issued in 1998 and the second edition published in 2014. Over the years it has been one of the most popular of the Eurachem guides. Since the release of the first edition, however, there have been many changes in terminology, working practices, reference documents and requirements. This third edition, produced by the Eurachem Method Validation Working Group, forms a thorough revision of the 2014 edition. This third edition includes a section on sampling and sample handling as ISO/IEC 17025:2017 introduced a focus on sampling associated with the testing or calibration being carried out by the laboratory and further guidance on assessing the calibration function has been included. The Guide is also now supported by a number of supplementary guidance documents – please see the section on supplementary guidance below.

Contents

This third edition includes guidance on:

• The importance of fitness for purpose;
• The concept of method validation and verification;
• How a method validation or verification study should be performed and how much should be done;
• Sampling and sample handling in relation to method validation;
• A thorough explanation of the various validation parameters (performance characteristics) and related topics;
• Follow-up on the validation study (reporting, use of performance data in Internal Quality Control);
• Documentation of analytical methods.

Annexes also describe the statistical basis of detection limits and analysis of variance for precision studies, and add a check list to aid users in selecting and determining the validity of a test kit.

In preparing this guidance, the Working Group has aimed at the right balance between giving a solid theoretical background for method validation studies and providing practical guidelines on how to plan, perform and evaluate such studies in the laboratories.

The approach is generic in the sense that the Guide does not focus on particular fields of application (food, environment, pharmaceuticals etc.). However, the guide includes references to a number of specific guides in fields where different practices have been developed and become common.

The guide also includes a full bibliography. Further literature references on method validation can be found in the section "Validation of analytical methods" in the Reading list on this website.

Availability

You can download the Guide here at no cost:

• Download the guide in English (Issued 2025) (pdf, 2.01 MB)

The second edition of this Guide is available in a number of translations. For details see previous editions below.

Citation

This publication should be cited* as:
"H. Cantwell (ed.) Eurachem Guide: The Fitness for Purpose of Analytical Methods – A Laboratory Guide to Method Validation and Related Topics, (3rd ed. 2025). Available from http://www.eurachem.org"

*Subject to journal requirements

Supplementary guidance

The supplementary guidance below gives additional guidance on method validation topics:

• Planning and reporting method validation studies. This supplement is in the form of a template which can be used to assist with planning the evaluation of the chosen performance characteristics
• Blanks in method validation. This short supplement describes the different types of blanks which may be used during method validation and provides guidance for situations where it may be difficult to obtain a suitable blank matrix.

Translations

Translation into other languages is permitted for members of Eurachem. Other offers of translation should be directed to the Eurachem Secretariat for permission. The Eurachem policy on maintenance and development of Eurachem guidance, available on the Policies page, gives further information on translation.

Previous version

The 2014 edition of this guide can be found here for reference.

Quality Assurance for Research and Development and Non-routine Analysis (1998)

Contents

This guide, produced by a joint Eurachem/CITAC working party representing industrial, academic, and governmental interests, promotes and describes the concepts of quality assurance in the non-routine environment. The guide promotes a nested approach to quality assurance, dealing with it at a general organisational level, a technical level and a project specific level. It is intended to promote the use of QA as an effective tool for establishing and maintaining quality in R&D and non-routine operations. It does not seek to set criteria for accreditation of R&D although there is a section describing various methods for third party assessment of quality systems. The guidance may form the basis on which accreditation criteria can be set in the future. The guidance is intended to complement the existing CITAC guide (CG1) which describes QA in the routine environment. It is primarily directed towards analytical chemistry establishments but is, in principle, applicable to other sectors. An extensive bibliography is included.

Availability

The English language version (edition 1.0 1998) is available from the UK National Measurement System Chemical and Biological Metrology programme.

Download the guide from this website (new window) (pdf, 203 kB).

Translations

A German language version can be downloaded from the Eurachem/DE website documents page. (Opens new Browser window).

Translation into other languages is permitted for members of Eurachem. Other offers of translation should be directed to the Eurachem Secretariat for permission. The Eurachem policy on maintenance and development of Eurachem guidance, available on the Policies page, gives further information on translation.