Validation is confirmation that a method of measurement, through assessment of performance characteristics, is suitable for its intended use. Services provided by NIST that support the use of valid methods include 1) the development and publication of Reference Measurement Procedures (RMP), including “Primary Methods”, and 2) production of validation SRMs that are used to verify adequate performance of these procedures.
RMPs are rigorously examined and qualified NIST methods that can be employed for specific chemical characterizations of materials, including the realization of SI units for measured chemical quantities. These RMPs span practical applications such as clinical diagnostics, food safety and nutrition, and the implementation of primary methods (i.e., coulometry and isotope ratio mass spectrometry [IRMS]). [Links to RMP project pages]
A validation SRM is typically prepared from a naturally-occurring or manufactured material (e.g., tissue, environmental matrices, industrial commodities, etc.) that has a matrix similar to those of intended test samples. These materials a) contain desired levels of the measurands of interest, b) have been processed to have uniform composition, and c) may have been modified for improved stability. During analytical method development, validation SRMs are used to evaluate whether the calibration relationship established for the measurement process is appropriate for test samples of similar concentration and matrix. When implementing a method in a given situation (particular equipment, reagents, analysts, etc.), validation materials are used to verify that the measurement process indeed provides the expected results. Use of a validation material provides confidence in the measurement process, but does not itself contribute to establishing metrological traceability.
CSD provides over 700 SRMs that are intended for use in method validation. These include reference materials for manufacturing, food nutrition, food safety, natural products, clinical diagnostics and metabolomics, environmental assessments, and material evaluations. [https://www.nist.gov/srm]