GB/T 15000.3-2023 Directives for the work of reference materials - Part 3: Reference materials - Characterization and assessment of homogeneity and stability
1 Scope
This document 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.
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 3534-2 Statistics - Vocabulary and symbols - Part 2: Applied statistics
ISO 3534-3 Statistics - Vocabulary and symbols - Part 3: Design of experiments
ISO Guide 30 Reference materials - Selected terms and definitions
ISO/IEC Guide 99 International vocabulary of metrology - Basic and general concepts and associated
terms (VIM)
Note: The International vocabulary of metrology will hereafter be referred to as the “VIM”.
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO Guide 30, ISO/IEC Guide 99, ISO 3534-2, ISO 3534-3 and the following apply. The definitions in ISO Guide 30 take precedence where more than one definition for the same term exists.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
——ISO Online browsing platform: available at http://www.iso.org/obp
——IEC Electropedia: available at http://www.electropedia.org/
3.1
reference material; RM
material, sufficiently homogeneous and stable with respect to one or more specified properties, which has been established to be fit for its intended use in a measurement process
Note 1: RM is a generic term.
Note 2: Properties can be quantitative or qualitative, e.g. identity of substances or species.
Note 3: Uses may include the calibration of a measurement system, assessment of a measurement procedure, assigning values to other materials, and quality control.
Note 4: ISO/IEC Guide 99:2007 has an analogous definition (5.13), but restricts the term “measurement” to apply to quantitative values. However, ISO/IEC Guide 99:2007, 5.13, Note 3 (VIM), specifically includes qualitative properties, called “nominal properties”.
[SOURCE: GB/T 15000.2-2019, 2.1.1]
3.2
certified reference material; CRM
reference material (RM) characterised by a metrologically valid procedure for one or more specified properties, accompanied by an RM certificate that provides the value of the specified property, its associated uncertainty, and a statement of metrological traceability
Note 1: The concept of value includes a nominal property or a qualitative attribute such as identity or sequence. Uncertainties for such attributes may be expressed as probabilities or levels of confidence.
Note 2: Metrologically valid procedures for the production and certification of RMs are given in, among others, ISO 17034 and ISO Guide 35.
Note 3: ISO Guide 31 gives guidance on the contents of RM certificates.
Note 4: ISO/IEC Guide 99:2007 has an analogous definition (5.14).
[SOURCE: GB/T 15000.2-2019, 2.1.2]
3.3
measurement model
mathematical relation among all quantities known to be involved in a measurement
[SOURCE: ISO/IEC Guide 99:2007, 2.48]
3.4
property value
value corresponding to a quantity representing a physical, chemical or biological property of an RM
[SOURCE: GB/T 15000.2-2019, 2.2.1]
3.5
certified value
value, assigned to a property of a reference material (RM), that is accompanied by an uncertainty statement and a statement of metrological traceability, identified as such in the RM certificate
[SOURCE: GB/T 15000.2-2019, 2.2.3]
3.6
indicative value; information value; informative value
value of a quantity or property of a reference material, which is provided for information only
Note: An indicative value cannot be used as a reference in a metrological traceability chain.
[SOURCE: GB/T 15000.2-2019, 2.2.4]
3.7
calibrant
reference material used for calibration of equipment or a measurement procedure
[SOURCE: GB/T 15000.2-2019, 2.1.21]
3.8
quality control material
reference material used for quality control of a measurement
[SOURCE: GB/T 15000.2-2019, 2.1.22]
3.9
isochronous stability study
experimental study of reference material stability in which units exposed to different storage conditions and times are measured in a short period of time
3.10
production
all necessary activities and tasks leading to the release and maintenance of an RM (certified or non-certified)
Note: Activities include, for example, planning, control, material handling and storage, material processing, assessment of homogeneity and stability, characterization, assignment of property values and their uncertainties, authorization and issue of RM certificates or other statements.
[SOURCE: GB/T 15000.2-2019, 2.3.7]
4 Symbols
a number of reference material units in a homogeneity study
d measurement bias
k coverage factor or (as subscript) index
