水分分析用認証標準物質NMIJ CRM 4228-aの開発

The National Metrology Institute of Japan (NMIJ) has developed and issued a certified reference material (CRM), NMIJ CRM 4228-a, having water content of 1 mg g−1, in a mixed solution of anisole and diethylene glycol dimethyl ether. The water content of the CRM was determined by coulometric and volumetric Karl Fischer titrations. Standard solutions for calibrations were prepared by the gravimetric mixing of water and the solvents. Both titration methods had valid precision, and the results obtained by them were statistically equivalent. The uncertainties arising from the analytical method, between-method, homogeneity, and stability were evaluated and reflected in the uncertainty of the certified value. The certified value of the CRM was 996 mg kg−1, its expanded uncertainty, calculated using a coverage factor of k = 2, was 20 mg kg−1. We have described the measurement procedures and assays of the water contents in relation to the International System of Units (SI) and the technical details of the characterization in this CRM. The newly developed CRM is particularly suitable for quality assurance and method validation for the measurement of water content, especially by coulometric and volumetric Karl Fischer titrations.