Analytical Sciences

Abstract − Analytical Sciences, 29(2), 247 (2013).

Development of a Certified Reference Material (NMIJ CRM 7512-a) for the Determination of Trace Elements in Milk Powder
Yanbei ZHU, Tomohiro NARUKAWA, Shin-ichi MIYASHITA, Takayoshi KUROIWA, Kazumi INAGAKI, Koichi CHIBA, and Akiharu HIOKI
National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan
A certified reference material (CRM), NMIJ CRM 7512-a, was developed for the determination of trace elements in milk powder. At least three independent analytical methods were applied to characterize the certified value of each element; all of these analytical methods were based on microwave acid digestions and carried out using different analytical instruments. The certified value was given on a dry-mass basis, where the dry-mass correction factor was obtained by drying the sample at 65°C for 15 to 25 h. The certified values in the units of mass fractions for 13 elements were as follows: Ca, 8.65 (0.38) g kg−1; Fe, 0.104 (0.007) g kg−1; K, 8.41 (0.33) g kg−1; Mg, 0.819 (0.024) g kg−1; Na, 1.87 (0.09) g kg−1; P, 5.62 (0.23) g kg−1; Ba, 0.449 (0.013) mg kg−1; Cu, 4.66 (0.23) mg kg−1; Mn, 0.931 (0.032) mg kg−1; Mo, 0.223 (0.012) mg kg−1; Rb, 8.93 (0.31) mg kg−1; Sr, 5.88 (0.20) mg kg−1; and Zn, 41.3 (1.4) mg kg−1, where the numbers in the parentheses are the expanded uncertainties with a coverage factor of 2. The expanded uncertainties were estimated considering the contribution of the analytical methods, the method-to-method variance, the sample homogeneity, the dry-mass correction factor, and the concentrations of the standard solutions for calibration. The concentrations of As (2.1 μg kg−1), Cd (0.2 μg kg−1), Cr (1.3 μg kg−1), Pb (0.3 μg kg−1), and Y (64 μg kg−1) were given as information values for the present CRM.