As any analytical chemist knows, a test method is only as reliable as the reference materials used. Authentication of reference materials in dietary ingredients is crucial, and can mean the difference between a botanical offering health benefits versus its similar-looking but poisonous cousin.
The following organizations provide botanical and chemical reference materials. This listing does not necessarily constitute an endorsement of these sources:
NIST (National Institute of Standards and Technology) defines reference material as follows:
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
- RM is a generic term.
- Properties can be quantitative or qualitative, e.g. identity of substances or species.
- Uses may include the calibration of a measurement system, assessment of a measurement procedure, assigning values to other materials, and quality control.
- A single RM cannot be used for both calibration and validation of results in the same measurement procedure.
- International Vocabulary of Metrology – Basic and General Concepts and Associated Terms has an analogous definition (VIM – ISO/IEC Guide 99:2007, 5.13), but restricts the term “measurement” to apply to quantitative values and not to qualitative properties. However, Note 3 of ISO/IEC Guide 99:2007, 5.13, specifically includes the concept of qualitative attributes, called “nominal properties”.
(ISO Guide 30:1992/Amd 1:2008)
Certified Reference Material (CRM) – Reference material characterized by a metrologically valid procedure for one or more specified properties, accompanied by a certificate that provides the value of the specified property, its associated uncertainty, and a statement of metrological traceability
- The concept of value includes qualitative attributes such as identity or sequence. Uncertainties for such attributes may be expressed as probabilities.
- Metrologically valid procedures for the production and certification of reference materials are given in, among others, ISO Guides 34 and 35.
- ISO Guide 31 gives guidance on the contents of certificates.
- VIM has an analogous definition (ISO/IEC Guide 99:2007, 5.14).
(ISO Guide 30:1992/Amd 1:2008)
Reference Material Certificate – Document accompanying a certified reference material stating one or more property values and their uncertainties, and confirming that the necessary procedures have been carried out to ensure their validity and traceability. (ISO Guide 30: 1992)
NIST Standard Reference Material® (SRM) – A CRM issued by NIST that also meets additional NIST-specific certification criteria and is issued with a certificate or certificate of analysis that reports the results of its characterizations and provides information regarding the appropriate use(s) of the material (NIST SP 260-136). Note: An SRM is prepared and used for three main purposes: (1) to help develop accurate methods of analysis; (2) to calibrate measurement systems used to facilitate exchange of goods, institute quality control, determine performance characteristics, or measure a property at the state-of-the-art limit; and (3) to ensure the long-term adequacy and integrity of measurement quality assurance programs. The terms “Standard Reference Material” and the diamond-shaped logo which contains the term “SRM,” are registered with the United States Patent and Trademark Office.