Strategies and Practicalities in the Production and Use of Gas Isotope Standard Materials
R M. Verkouteren
Isotopic Reference Materials (RMs) are a critical component in the assurance of laboratory analytical quality, and have been applied to growing needs in environmental monitoring, medical and industrial applications, consumer protection, and in the traceability of measurements to primary standards. Gas isotope RMs are especially critical for applications involving the light elements (H, C, N, O, S), which are among the most abundant and chemically diversified elements in nature and industry. This paper presents a practical guide to the production and use of gas isotope RMs that have been developed at the National Institute of Standards and Technology (NIST) in accordance with guidelines of the international Organization for Standardization (ISO) and in partnership with the International Atomic Energy Agency (IAEA). Assessment of needs, gas selection criteria, safety considerations, measurement strategy, data normalization, and a Web-based interactive data reduction algorithm are also discussed. By utilizing gas isotope RMs as a part of a total quality assurance system, improvements in reproducibility of measurement may be realized across laboratories. An example is presented using the carbon dioxide materials RM8562, RM 8563, and RM 8564, where normalization of data improved interlaboratory reproducibility by a factor of three or more.