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International Comparisons for Chemical Measurements


Because of NIST's role as the National Metrology Institute (NMI) in the U.S., the Chemical Sciences Division's measurement capabilities must be benchmarked against the capabilities of NMIs worldwide as required by a Mutual Recognition Arrangement (MRA) established in 1999. The MRA provides a framework for obtaining reliable quantitative information on the comparability of measurement services provided by all NMIs, thereby providing governments and other parties with a technical foundation for wider agreements related to international trade, commerce, and regulatory affairs. The Chemical Sciences Division actively participates in the International Committee of Weights and Measures (CIPM) Consultative Committee for Amount of Substance – Metrology in Chemistry and Biology (CCQM) comparisons, which address chemical and biological measurement-related issues important for international trade, environmental, health, and safety-related decision making. We have also established a limited number of strategic bilateral collaborations and/or intercomparisons with NMIs around the world to demonstrate comparability of measurements and/or to cooperate in the development of reference materials.


International agreements and decisions concerning trade and our social well-being increasingly require mutual recognition of measurements and tests among nations. The Mutual Recognition Arrangement (MRA) on national measurement standards and calibration and measurement certificates issued by NMIs rests upon the assumption of equivalence of national measurement standards in each country. In October 1999, the directors of NMIs for its original 38 member states of the Meter Convention and two international organizations signed the MRA; nearly 100 countries and associates now have signed the MRA. The MRA provides an open, transparent, and comprehensive framework for obtaining reliable quantitative information on the comparability of measurement services provided by the signatory NMIs.

Signatories to this MRA have the following responsibilities: (1) participate in relevant international comparisons, known as key comparisons, (2) participate in any relevant supplementary international comparisons of measurements, and (3) document the existence of a quality system and demonstrations of competence for its measurement services to customers. The expected outcome from these activities is to provide statements for each signatory of its calibration and measurement capabilities (CMCs) in a publically-available database. NIST has taken a leadership role in the CCQM and in the Chemical Metrology Working Group of the Interamerican System for Metrology (SIM) to assure the equitable and metrologically sound implementation of this MRA.

The CCQM currently has ten working groups: (1) Inorganic Analysis, (2) Electrochemical Analysis, (3) Gas Analysis, (4) Organic Analysis, (5) Surface Analysis (6) Protein Analysis, (7) Cell Analysis, (8) Nucleic acid Analysis, (9) Key Comparison and CMC Quality, and (10) Strategic Planning. These working groups are responsible for selecting and overseeing the operation of key comparisons, in which participating laboratories demonstrate their measurement or material preparation capabilities. Staff members of the Chemical Sciences Division (CSD) are involved in the various activities within several working groups. Since its inception over 20 years ago, over 150 key comparison studies and a similar number of pilot studies have been conducted under the auspices of the CCQM. CSD has participated in a large majority of these key comparisons, serving as the coordinating laboratory in nearly half of these key and pilot studies.

Participation in CCQM key comparisons is generally limited to NMIs with well-established chemical metrology programs. Within SIM, several NMIs have well-established programs; however, many NMIs are still developing their capabilities. To effectively address the unique needs of all 32 countries within SIM, whose capabilities in chemical metrology span a very broad range, the SIM program has focused on training and capability assessment rather than on participation in MRA-driven key and supplemental comparisons. The Chemical Sciences Division has served as host to numerous guest scientists from NMIs across SIM NMIs for periods of several months to a year. CSD has provided training in all aspects of chemical metrology, ranging from the preparation of primary gas mixtures to the development of trace-level elemental detection methods to the accurate measurement of vitamin metabolite levels in human blood samples. As a more recent example, CSD is providing SIM NMIs with in-depth classroom and hands-on laboratory training at NIST in the form of 1-week course for implementation of isotope dilution/mass spectrometry methods in the application of clinical marker measurements.

In addition to these regional activities, we have also established several strategic bilateral collaborations and intercomparisons with NMIs around the world. For example, since 1992 we have collaborated with the Netherlands Measurement Institute (NMi) to determine the equivalence of primary gas standards, resulting in a formal "Declaration of Equivalence" that is recognized by the U.S. EPA and European environmental regulatory bodies as documenting the equivalence between numerous NIST and NMi primary gas mixture suites. For nearly a decade, the CSD has advanced a partnership with the National Institute of Metrology, Standardization and Industrial Quality (INMETRO), the National Metrology Institute of Brazil. More recently, NIST and INMETRO signed a Cooperative Research Agreement to exchange technical information and capabilities related to chemical and physical measurement sciences, alternative energy sources, and measurement standards, including reference data and materials. In July 2013, a renewed agreement was also signed between NIST and the European Commission’s Joint Research Centre (JRC) Institute for Reference Materials and Measurements (IRMM) in Geel, Belgium to collaborate and coordinate with their research and development programs in metrology. This agreement includes cooperative research on modern measurements and their quality assurance and technical cooperation in the preparation and characterization of certified reference materials that span broad measurement areas, such as healthcare, food safety, environmental protection and nanotechnology.

Created April 7, 2009, Updated December 11, 2019