Conventional and new traceability schemes of organic standards for safe water supply in Japan

Metrological traceability to the International System of Units (SI) is required to ensure reliability of analytical results. For this purpose, SI-traceable standard solutions of respective analytes are essential for common analytical methods such as chromatography. However, it is not so easy to fulfill demands due to the existence of a vast number of targets, especially in the case of organic analysis. Because high-purity organic materials which are raw materials of standard solutions must be characterized by compound-independent methods, the mass balance approach (subtraction method) and the primary methods of measurement (e.g. the freezing point depression method and titrimetry) are used. Recently, quantitative NMR (qNMR) has been popularized. The National Metrology Institute of Japan, the National Institute of Advanced Industry, Science and Technology (NMIJ/AIST) has been supplying many types of reference materials including high-purity organic materials and organic standard solutions. In 2015, the demand of traceable reference materials for drinking water analyses rose by an amendment of a notification under the Waterworks Act of Japan. In this manuscript, NMIJ's efforts such as supplying certified reference materials and providing calibration services in this field are outlined. Among them, direct characterization of multi-components standard solutions by qNMR/chromatography or post-column reaction gas chromatography is an efficient approach to realize new traceability schemes without the step of a purity assessment of each reference material.