Do I Need a Reference Material or a Certified Reference Material?

Water drop from pipette into blue test tubes.

Laboratories and laboratory-related organizations use reference materials (RMs) and certified reference materials (CRMs) for a variety of reasons, such as ensuring the validity of results, method validation, method verification, and equipment calibration. It is important for laboratories to purchase and evaluate RMs and CRMs to ensure they are fit for the laboratory’s intended purpose. ISO/IEC 17025:2017, section 6.6.2 requires laboratories to have a procedure and retain records for defining, reviewing, and approving the laboratory’s requirements for externally provided products, as well as ensuring that externally provided products conform to these defined requirements.

Reference Material vs. Certified Reference Material

A reference material 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 [ISO Guide 30]. A certified reference material is a reference material characterized 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 [ISO Guide 30]. RMs and CRMs are typically purchased by reference material producers (RMPs) that are accredited to ISO 17034 for a defined scope of accreditation. Purchasing RMs and CRMs from an ISO 17034 accredited RMP provides confidence that the RM or CRM will be stable, homogeneous, and include the necessary information for use.

You can learn more in our blog post Reference Material (RM) vs Certified Reference Material (CRM).

When to Use Reference Materials or Certified Reference Materials

RM is a generic term that includes any materials produced by an RMP. Where laboratories may run into issues is when metrological traceability is needed in measurements performed by the laboratory. This is when the laboratory must determine if an RM or a CRM should be used because there are differences between RMs and CRMs, as described in the definitions of each. When metrological traceability of a measurement is necessary, then CRMs should be used.

AttributeReference MaterialCertified Reference Material
Certified valueNoYes
Metrological traceabilityOptionalYes
Measurement uncertaintyOptionalYes

The main consideration when determining if an RM or a CRM should be used is to ask if metrological traceability and measurement uncertainty are needed for the measurements being performed by the laboratory. If so, CRMs should be used. Another consideration in determining what RMs or CRMs to purchase is the matrix of the RM or CRM. The matrix should match the product matrix being measured by the laboratory. Additionally, consideration should be given to the appropriateness of the property value or certified value to ensure it is in the range of the products being measured.

Further Help Evaluating RMs and CRMs

If you still have questions regarding purchasing and evaluating RMs and CRMs, including evaluating RM and CRM documents, ANAB has prepared a guidance document: GD 2708, Guidance on Purchasing and Evaluating Reference Materials. All ANAB-accredited RMPs can be found in the online directory here

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