Certified reference materials
From Wikipedia, the free encyclopedia
Certified Reference Materials (CRMs) are ‘controls’ or standards used to check the quality and traceability of products. A reference standard for a unit of measurement is an artifact that embodies the quantity of interest in a way that ties its value to the reference base for calibration.
At the highest level, a primary reference standard is assigned a value by direct comparison with the reference base. For example, mass is defined by an artifact maintained by the Bureau International des Poids et Mesures in Sèvres, France. A primary standard is usually under jurisdication of a national standards body.
Since most analytical instrumentation is comparative, it requires a sample of known composition (Reference Material) for accurate calibration. These Reference Materials as produced under stringent manufacturing procedures and differ from laboratory reagents in their certification and the traceability of the data provided.
Quality management systems involving laboratory accreditation under national and international accreditation/certification standards such as ISO 9000 and ISO 17025 require the use of Reference Materials.
Whilst Certified Reference Materials are preferred, their availability is limited. - The available Reference Materials generally differ only in the detail provided on the certificate.
Definitions as ISO Guide 30 (1992 Edition).
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[edit] Reference Material (RM)
A material or substance one or more of whose property values are sufficiently homogeneous and well established to be used for the calibration of an apparatus, the assessment of a measurement method, or for assigning values to materials.
[edit] Certified Reference Material (CRM)
A Reference Material, accompanied by a certificate, one or more of whose property values are certified by a procedure which establishes its traceability to an accurate realisation of the unit in which the property values are expressed and for which each certified value is accompanied by an uncertainty at a stated level of confidence.
[edit] Manufacture
Production of CRMs is split into two categories: Calibrants and matrix CRMs. Calibrants are pure standards used for calibrating instruments. These are usually produced by commercial producers (Merck CMBH, Sigma Aldrich, Biopure). Matrix CRMs contain an analyte in a sample (e.g. lead in fish). Due to the difficulty in its production and value assignment, these are usually produced by national or transnational metrology institutes like NIST (USA), BAM (Germany), KRISS (Korea) and IRMM (European Commission).
[edit] References
- ISO Guide 35: 1989 - Certification of reference materials - General and statistical principles
- ISO Guide 31: 2000 - Contents of certificates & labels of reference materials
- ISO Guide 33: 1989 - Uses of certified reference materials
- ISO Guide 34: 2000 - General requirements for the competence of reference material producers
