Preparation of Five Selenium-rich Soil Reference Materials, Their Se, Cr, Ni, Zn, Cd, Pb Mass Fraction Certifications and A Study of Se Geochemical Fractionation

This paper describes the preparation and characterization procedure of the certified reference materials (CRMs) (GBW07900, GBW07901, GBW07902, GBW07903, and GBW07904), of which the raw materials deriving from five seleniferous regions of China. Mass fractions of Se, Cr, Ni, Cu, Zn, Cd and Pb in the samples were determined, and two CRMs GBW07901 and GBW07902 were preliminarily characterized for Se geochemical fractionation measurement. The samples exhibited homogeneity and stability, and the interlaboratory comparison scheme was accomplished by ten ISO accredited laboratories. The certified values and expanded uncertainties (k = 2) for the selenium mass fractions in GBW07900-GBW07904 are 19.5 +/- 2.1 mu g g-1, 9.4 +/- 1.4 mu g g-1, 2.7 +/- 0.4 mu g g-1, 0.91 +/- 0.10 mu g g-1 and 0.83 +/- 0.07 mu g g-1, respectively. The mass fractions of Cr, Ni, Cu, Zn, Cd and Pb of the CRMs range from 92-488 mu g g-1, 23-157 mu g g-1, 26-157 mu g g-1, 74-248 mu g g-1, 0.04-11.8 mu g g-1 and 13.7-36 mu g g-1, respectively.