Feasibility study for the certification of the contents of inorganic selenium (IV) and (VI) (selenite and selenate) species and total inorganic selenium in artificial freshwater reference materials†

Abstract

This paper describes the preparation of two artificial solutions containing inorganic SeIV (selenite) and SeVI (selenate), the homogeneity and stability studies and the analytical work performed for the tentative certification of the contents of total inorganic selenium, selenite and selenate. The results submitted by a group of EU laboratories are discussed, in addition to the methods used to determine the selenium species in solutions containing low (6 µg l^–1) and high (50 µg l^–1) analyte levels. Although the good agreement obtained by the laboratories would have permitted certification, the Se species were found not to be stable over a long-term period (36 months) in polypropylene bottles which hence hampered certification of these reference materials.