ISO Guide 35-2017 PDF

Full title and description

ISO Guide 35:2017 — Reference materials — Guidance for characterization and assessment of homogeneity and stability. This document provides guidance and recommended approaches for planning, designing and performing the homogeneity, stability and characterization studies needed when producing reference materials (including guidance on value assignment, uncertainty evaluation and metrological traceability).

Abstract

ISO Guide 35:2017 explains concepts and provides approaches for: assessment of homogeneity; assessment and management of stability risks for properties of interest; characterization and value assignment of reference material properties; evaluation of uncertainty for certified values; and establishing metrological traceability of certified property values. The Guide offers brief guidance on commutability and qualitative properties but does not provide full statistical methods for multivariate quantities.

General information

• Status: Withdrawn (superseded by ISO 33405:2024).
• Publication date: August 2017 (2017-08).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 71.040.30 (Chemical technology — Chemical reagents / Reference materials).
• Edition / version: Fourth edition (Edition 4, 2017).
• Number of pages: 105 pages (as published).

Scope

This Guide covers recommended approaches and concepts for the production of reference materials (RMs), specifically the experimental design and statistical evaluation needed for homogeneity studies, stability assessment and monitoring, characterization/value assignment of properties (including uncertainty evaluation), and demonstrating metrological traceability. It is intended to support the requirements of RM producers and to complement ISO 17034; it does not address multivariate spectral data nor provide exhaustive statistical methods for qualitative measurands.

Key topics and requirements

• Project design and feasibility for RM production (acquisition of starting material, processing and packaging).
• Design and statistical evaluation of homogeneity studies (sampling schemes, required minimum units, power analysis and appropriate measurement procedures).
• Stability assessment and risk management for property changes over time; guidance on stability-monitoring programs.
• Characterization and value assignment approaches (single-laboratory and multi-laboratory strategies, purity/identity considerations, method selection and commutability considerations).
• Evaluation and combination of uncertainty contributions for certified property values and guidance on coverage intervals.
• Practical annexes with statistical approaches, worked examples and uncertainty-evaluation examples.

Typical use and users

Used by reference material producers, national metrology institutes, accreditation bodies, testing and calibration laboratories, regulators and organizations that develop or rely on certified reference materials for method validation, calibration and quality assurance. The Guide is applied when planning homogeneity and stability studies, assigning property values and reporting uncertainties to users of RMs. For broader context on the role of CRMs and RMs in laboratory accreditation and traceability, see reference materials guidance and explanatory resources.

Related standards

ISO Guide 35:2017 is linked with and intended to support ISO 17034 (requirements for competence of RM producers) and ISO Guide 30 (terms and definitions for reference materials). In 2024 the Guide was revised and the approaches were published under the new series numbering (ISO 33405:2024 and other ISO 3340x documents); related documents from ISO/TC 334 include ISO 33403:2024, ISO 33406:2024 and ISO/TR 33402. Users should refer to the current ISO 3340x series for the latest, published requirements and approaches.

Keywords

reference material, certified reference material, RM, CRM, homogeneity, stability, characterization, value assignment, measurement uncertainty, metrological traceability, commutability, sampling, statistical design.

FAQ

Q: What is this standard?

A: ISO Guide 35:2017 is an international guidance document for the characterization and assessment of the homogeneity and stability of reference materials, used to support the production and certification of RMs.

Q: What does it cover?

A: It covers experimental design and statistical approaches for homogeneity studies, stability assessment and monitoring, approaches to characterization and value assignment (single- and multi-laboratory), evaluation of uncertainty for certified values, and establishing metrological traceability. It also provides informative annexes with statistical and worked examples.

Q: Who typically uses it?

A: Reference material producers, calibration and testing laboratories, national metrology institutes, accreditation bodies and regulators—any organization involved in producing, certifying, using or assessing reference materials.

Q: Is it current or superseded?

A: ISO Guide 35:2017 has been withdrawn and its approaches have been superseded and republished in the ISO 33405:2024 document (and the wider ISO 3340x series). Users should consult ISO 33405:2024 for the current, published approaches.

Q: Is it part of a series?

A: Yes — it belongs to ISO guidance/documents on reference materials (work of ISO/TC 334). The 2017 Guide sits historically with ISO Guide 30 and ISO 17034; the current series of documents replacing and extending the Guide 35 content is identified under ISO 3340x (for example ISO 33405:2024).

Q: What are the key keywords?

A: Key keywords include: reference material, certified reference material (CRM), homogeneity, stability, characterization, value assignment, measurement uncertainty, metrological traceability, commutability, sampling and statistical design.