Speciation analysis of selenium allowed determination of inorganic
selenium (Pyrzynska, 2002) Se(IV) and Se(VI) occurring in the
preparations studied (Table 1). Inorganic forms were determined
in phosphate buffer. All 86 of the preparations were subjected to
analysis. In 36, no inorganic selenium was found (Fig. 5). In 25
preparations, Se(IV) and selenium-organic compounds were found;
in 15, Se(VI) and selenium-organic compounds were observed; in
nine, selenium occurred as both Se(IV) and Se(VI) as well as in inorganic
compounds. It should be, however, be noted that, in terms of
potential selenium bioavailability, the occurrence of inorganic
compounds is less favorable than selenium-organic compounds
(Amoako et al. 2009). In other studies of selenium dietary
supplements, the authors found both inorganic forms Se(IV) and,
predominantly, Se(VI), as well as selenium-organic compounds,
mainly as selenomethionine with traces of selenocysteine (Hsieh
& Jiang, 2013).