Control materials for selenium in serum suitable for speciation studies

Abstract

Selenium is an essential element which importance for human health is widely recognised. At present, Se status is assessed by either determination of total Se or glutathione peroxidase activity, but increasing attention is paid to the dosage of other Se species. From an analytical point of view, the presence of different Se species may influence even the determination of total Se. Most analytical techniques suffer from interferences and require control (CMs) and reference (RMs) materials for their validation. At present, the preparation of materials with different Se concentrations mainly relies on the addition of inorganic Se compounds to human or animal serum. However, the analytical behaviour of added inorganic Se may be different from that of native organic Se species, thus affecting the evaluation of method and laboratory performances. CMs at different Se concentrations were prepared without the addition of inorganic Se by pooling batches of serum with low and high Se content obtained from two different animal species (cow and horse) and used for two years in the Italian External Quality Assessment Scheme (EQAS) for trace elements in biological fluids. The results obtained in this EQAS are reported and compared with those obtained by the same laboratories on CMs spiked with inorganic Se. CMs prepared according to this protocol could be suitable for the assessment of methods for the speciation of Se in serum.