Towards method validation for selenium speciation analysis in human serum

Se is one of the most investigated trace essential elements in the last years, mostly due to its cancer prevention properties. Nevertheless, the accurate determination of its biologically active species present in human serum, such as selenoproteins (SeProt), is currently a challenging task. This is because of the lack of appropriate quantification standards, certified reference materials (CRMs) and/or reference measurement methods. Additionally, most of the methods developed so far for the determination of SeProt in human serum were applied to the analysis of control (volunteers) serums, which are not available to other laboratories, therefore making the method inter-comparison virtually impossible. We present here for the first time indicative levels of SeProt in a commercially available human serum, namely the BCR-637 CRM (with certified level of total Se). The selenium levels associated with glutathione peroxidase (GPx), selenoprotein P (SelP) and selenoalbumin (SeAlb) in this serum were calculated by means of the results obtained by using 13 different analytical methods on the basis of (double column) affinity HPLC coupled to ICP-MS. The indicative levels of SeProt in the BCR-637 serum can be used as preliminary reference values for validation of methods dealing with the determination of SeProt in human serum.