According to ISO [ISO REMCO 1995], A Reference Material (RM) is a �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.�
A Certified Reference Material (CRM) is, again according to ISO [ISO REMCO, 1995], 'A reference material characterised by a metrologically valid procedure for one or more specified properties, accompanied by a certificate that states the value of the specified property, its associated uncertainty, and a statement of metrological traceability.'
A CRM differs from an RM in that:
- the value certified is traceable to fundamental units (and is therefore acceptable for calibration or method validation in international trade);
- it includes a stated uncertainty.
RMs guarantee neither.