Analytical Sciences

Development of a Certified Reference Material (NMIJ CRM 7203-a) for Elemental Analysis of Tap Water

Yanbei ZHU,* Tomohiro NARUKAWA,* Kazumi INAGAKI,* Shin-ichi MIYASHITA,* Takayoshi KUROIWA,* Tomoko ARIGA,* Izumi KUDO,* Masae KOGUCHI,* Sung Woo HEO,** Jung Ki SUH,** Kyoung-Seok LEE,** Yong-Hyeon YIM,** and Youngran LIM**

*National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan
**Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea

A certified reference material (CRM), NMIJ CRM 7203-a, was developed for the elemental analysis of tap water. At least two independent analytical methods were applied to characterize the certified value of each element. The elements certified in the present CRM were as follows: Al, As, B, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Rb, Sb, Se, Sr, and Zn. The certified value for each element was given as the (property value ± expanded uncertainty), with a coverage factor of 2 for the expanded uncertainty. The expanded uncertainties were estimated while considering the contribution of the analytical methods, the method-to-method variance, the sample homogeneity, the long-term stability, and the concentrations of the standard solutions for calibration. The concentration of Hg (0.39 μg kg⁻¹) was given as the information value, since loss of Hg was observed when the sample was stored at room temperature and exposed to light. The certified values of selected elements were confirmed by a co-analysis carried out independently by the NMIJ (Japan) and the KRISS (Korea).

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