Metrological traceability of matrix reference materials

Establishment and demonstration of the metrological traceability of measurement results is one of the main goals of testing laboratories. In physicochemical measurements, the problem of establishing metrological traceability is still far from being solved and is very relevant. One of the basic principles of quantitative chemical analysis, as well as other types of measurements, is to ensure the traceability to the “standard” of the corresponding unit of physical quantity, but the unit of quantity of a substance “mole” does not have a standard. At the same time, the amount of a chemical element or stoichiometric com­pound in moles can be expressed in the units of mass — kilogram, and vice versa, the mass of any element or stoichiometric compound can be expressed in moles, using standard reference data on the atomic weight of chemical elements and their isotopes. When determining the chemical composition of matrix materials, as a rule, the mass fraction of the analyzed element (component) is determined. Algorithms for calculating the results of physical and chemical measurements are considered from the viewpoint of the metrological traceability using the example of individual methods. It is shown that the results of measure­ments of the mass fraction of elements can be traced to the standard unit of mass of SI system “kilogram.” Measuring instruments that have been verified do not always meet the requirements of GOST ISO/IEC 17025 for metrological traceability. For a significant part of universal individually calibrated analytical in­struments, the normalized metrological characteristics indicate only their capabilities and are only indi­rectly related to the uncertainty of measurements performed using these instruments. Certain difficulties are attributed to the necessity of confirming the metrological traceability of the values of certified refer­ence materials. The variants of statements on metrological traceability presented in the certificates of for­eign manufacturers of certified reference materials are considered. In conclusion, the authors provide a statement on the traceability of the certified characteristics of certified reference materials produced by ICRM.

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