カドミウム分析用白米粒及び玄米粒標準物質の均質性と安定性の評価

• Published in: Bunseki kagaku Vol. 68; no. 2; pp. 133 - 137
• Main Authors: 乾, 哲朗, 大渕, 敦司, 神戸, 亮, 中村, 利廣
• Format: Journal Article
• Language: Japanese
• Published: Tokyo 公益社団法人 日本分析化学会 05.02.2019; Japan Science and Technology Agency
• Subjects: Atomic absorption analysis; Bottles; Grain; Homogeneity; Mapping; Physicists; Product design; Reference materials; Regression analysis; Stability analysis; Sulfuric acid; Variance analysis; X-ray fluorescence
• ISSN: 0525-1931
• DOI: 10.2116/bunsekikagaku.68.133

The homogeneity and stability of reference materials for the determination of Cd in white and brown rice grains were evaluated using atomic absorption spectrometry (AAS) after HNO3-H2SO4 digestion. Two kinds of rice grain reference materials were prepared by adding 100 g each of white and brown rice grains (both from Niigata prefecture, Japan) to 750 mL of methanol containing 40 μL of 1000 mg L−1 Cd standard solution (40 μg as Cd), and then heating them at 300°C for 1 h on a hot plate to evaporate the solvent. Each rice grain reference material (100 g) was packed in 10 glass bottles (10 g each). The homogeneity of Cd in the rice grain reference materials was estimated by an analysis of the variance after the Cochran test. A total of 9 samples (3 samples each from 3 bottles) were subjected to the homogeneity test. There was no significant difference between the within-bottle and between-bottle variances, indicating that both rice grain reference materials were sufficiently homogeneous. The stability of Cd in the rice grain reference materials was estimated by regression analysis. For a stability study, 6 bottles were stored in the dark at room temperature for a period of 6 months. The rice grain reference materials were stable for 5 months for white rice grain and for 6 months for brown rice grain. Elemental mapping images of the Cd of a longitudinal section of a white rice grain and a brown rice grain, using a micro-X-ray fluorescence instrument, suggested that the added Cd is present in the outer layers of the rice grain reference materials. The rice grain reference materials with a Cd concentration of approximately 0.31 mg kg−1, prepared in this study, can be used for validating the AAS determination of Cd in white and brown rice grains.