FEASIBILITY STUDY FOR THE CERTIFICATION OF THE CONTENTS OF INORGANIC SELENIUM(IV) AND SELENIUM(VI) (SELENITE AND SELENATE) SPECIES AND TOTAL INORGANIC SELENIUM IN ARTIFICIAL FRESH-WATER REFERENCE MATERIALS

This paper describes the preparation of two artificial solutions conta ining inorganic Se-IV (selenite) and Se-VI (selenate), the homogeneity and stability studies and the analytical work performed for the tenta tive certification of the contents of total inorganic selenium, seleni te and selenate, The results submitted by a group of EU laboratories a re discussed, in addition to the methods used to determine the seleniu m species in solutions containing low (6 mu g l(-1)) and high (50 mu g l(-1)) analyte levels. Although the good agreement obtained by the la boratories would have permitted certification, the Se species were fou nd not to be stable over a long-term period (36 months) in polypropyle ne bottles which hence hampered certification of these reference mater ials.