Volume 19, Issue 1 (January 1991)
What Constitutes a Reference Material and How Is It Certified?
There has been much discussion in recent years regarding the definitions of Reference Material (RM) and Certified Reference Material (CRM). The authors give their interpretations of the definitions given in the Guides published by the International Organization for Standardization (ISO) as applied to the metals analysis laboratory.
The objective of the paper is to help users of RMs make their own assessment of the status of an RM by a critical evaluation of the certificate, or other document, which is issued by the certifying body. Information is also given regarding the procedures generally in use by producers of CRMs for the metals industry to ensure the accuracy and precision of the CRM.
The certification procedure includes the planning of the project, the selection of participating laboratories, and the issue of detailed instructions for the certification analysis. Procedures for the technical and statistical evaluation of the results are also discussed, together with the resolution of any discrepancies between the results obtained in different laboratories.
The authors' views are based on many years of experience in the preparation of CRMs for the metals industry, both on a U.K. national basis and more recently on a European basis.