ISO/TC 334 - Reference materials

ISO/Guide 35:2017 explains concepts and provides approaches to the following aspects of the production of reference materials: - the assessment of homogeneity; - the assessment of stability and the management of the risks associated with possible stability issues related to the properties of interest; - the characterization and value assignment of properties of a reference material; - the evaluation of uncertainty for certified values; - the establishment of the metrological traceability of certified property values. The guidance given supports the implementation of ISO 17034. Other approaches may also be used as long as the requirements of ISO 17034 are fulfilled. Brief guidance on the need for commutability assessment (6.11) is given in this document, but no technical details are provided. A brief introduction for the characterization of qualitative properties (9.6 to 9.10) is provided together with brief guidance on sampling such materials for homogeneity tests (Clause 7). However, statistical methods for the assessment of the homogeneity and stability of reference materials for qualitative properties are not covered. This document is also not applicable to multivariate quantities, such as spectral data.

ISO 17034:2016 specifies general requirements for the competence and consistent operation of reference material producers. ISO 17034:2016 sets out the requirements in accordance with which reference materials are produced. It is intended to be used as part of the general quality assurance procedures of the reference material producer. ISO 17034:2016 covers the production of all reference materials, including certified reference materials.

ISO/TR 16476:2016 investigates, discusses, and specifies further, the general principles of establishing traceability of measurement results laid down in the Joint BIPM, OIML, ILAC and ISO Declaration on Metrological Traceability [1], in particular for values assigned to (certified) reference materials. The document covers the following topics: a) a study into existing principles for, and requirements to, the traceability of the value assigned to the property of a (C)RM, with a specific view to the current definition of metrological traceability given by the 2007 edition of the VIM (published also as JCGM 200:2008[2] and ISO/IEC Guide 99:2007[21]); b) the development of a sensible, widely applicable approach to the understanding of the traceability of a value assigned to (C)RM property; c) recommendations on how traceability should be established, demonstrated, and reported on certificates and other documents accompanying (C)RM. The developed approach is exemplified for measurement procedures not covered earlier by other guidance documents on the topic.

ISO/Guide 31:2015 is intended to help reference material (RM) producers in preparing clear and concise documentation to accompany an RM. It lists and explains mandatory, recommended and other categories of information to be considered in the preparation of product information sheets and RM certificates. This information can be used by RM users and other stakeholders in confirming the suitability of an RM or certified reference material (CRM). ISO/Guide 31:2015 also contains the minimum requirements for a label attached to the RM container.

ISO/TR 79:2015 summarizes the state of the art of the production and certification or characterization of qualitative property reference materials (RMs). The need for guidance documents for the production of RMs certified for qualitative properties was recognized by many experts. At the same time, the available information was found to be too immature to develop an internationally accepted guidance document. Additionally, the lack of an international vocabulary for terms and definitions for qualitative properties made it more difficult for the experts from various testing areas to communicate with each other. ISO/TR 79 summarizes the available expertise. It aims to contribute to the on-going discussion on nominal properties and the production of such RMs. The investigation of nominal properties is referred to differently in various specialized areas (examination, classification, identification, testing, observation, etc.). ISO/TR 79 tries to foster the future development of an internationally harmonized guidance document.

ISO Guide 30:2015 recommends terms and definitions that should be assigned to them when used in connection with reference materials, with particular attention to terms that are used in reference material certificates and corresponding certification reports.

ISO Guide 33:2015 describes good practice in using reference materials (RMs), and certified reference materials (CRMs) in particular, in measurement processes. These uses include the assessment of precision and trueness of measurement methods, quality control, assigning values to materials, calibration, and the establishment of conventional scales. This Guide also relates key characteristics of various types of RMs to the different applications. For CRMs, the metrological traceability of the property values to international scales or other measurement standards has been established. For RMs not being CRMs, this kind of traceability of property values has often not been established. Nevertheless, these RMs can still be used for assessing parts of measurement procedures, including evaluating various levels of precision Mainstream applications of RM include precision control, bias assessment, calibration, preparation of calibration RMs and maintaining conventional scales. NOTE Not all types of RMs can be used for all indicated purposes. The preparation of RMs for calibration is also part of the scope of ISO Guides 34 and 35. The treatment in this Guide is limited to the fundamentals of small-scale preparation of RMs and the value assignment, as used by laboratories to calibrate their equipment. Larger scale production of such RMs, with the possible aim of distribution is beyond the scope of this Guide. This type of activity is covered in ISO Guides 34 and 35. The development of working standards, as used in, e.g. natural gas analysis, clinical chemistry, and the pharmaceutical industry is not covered in this Guide. This type of activity is covered in ISO Guides 34 and 35.

ISO Guide 80 outlines the essential characteristics of reference materials for quality control (QC) purposes, and describes the processes by which they can be prepared by competent staff within the facility in which they will be used (i.e. where instability due to transportation conditions is avoided). The content of this Guide also applies to inherently stable materials, which can be transported to other locations without risk of any significant change in the property values of interest. The primary audience for this Guide is laboratory staff who are required to prepare and use materials for specific in-house quality control applications. Preparation of QCMs, where transportation is a necessary component of the supply chain, such as laboratory sites at different locations or for proficiency testing schemes, should conform to the relevant requirements of ISO Guides 34 and 35. The description of the production of reference materials (RMs), as detailed in ISO Guide 34 and ISO Guide 35 is also applicable to the preparation of quality control materials (QCMs). However, the requirements for "in-house" QCMs are less demanding than those for a certified reference material (CRM). The preparation of QCMs should involve homogeneity and stability assessments, and a limited characterization of the material to provide an indication of its relevant property values and their variation, prior to use. This document provides the quality criteria that a material should fulfil to be considered fit-for-purpose for demonstrating a measurement system is under statistical control. Guidance on uses of such materials is not included in this Guide. The layout and structure of this Guide provides general information on the preparation of QCMs in the main chapters, with specific case studies covering a range of sectors in the annexes. The case studies are not complete "process manuals" but are included to highlight some of the key considerations when preparing QCMs. The case studies vary in complexity and detail, including sector specific terminology, but provide a range of information for laboratory staff to draw from. It is expected that those involved in QCM preparation will have some knowledge of the type of material to be prepared and be aware of any potential problems due to matrix effects, contamination, etc.

ISO/TR 11773:2013 contains an inventory of problems and recommendations related to the transport, import and export of non-nuclear, non-radioactive reference materials, specifically for the packaging, labelling, and documenting of the shipments in order to comply with legal requirements. It does not explain detailed rules such as for labelling according to the Globally Harmonized System (GHS).

ISO/TR 10989:2009 covers: the results of a study into, and comparison between, existing classification and categorization schemes for reference materials, the development of reference material (RM) features and characteristics upon which a harmonized and consistent categorization scheme could be based, and approaches for making the categorization scheme adaptive to new RM needs and developments. The development of a harmonized categorization scheme aims at facilitating a transparent and comparable presentation of reference materials by producers, and the identification of reference materials by users. The intended categorization scheme was conceived to meet the needs of modern forms of information presentation and retrieval, i.e. internet-based catalogues and databases, and has been developed specifically with the view to being used this way.