Simple method for the accurate determination of selenium in serum by using inductively coupled plasma mass spectrometry

A simple 1+15 dilution of 200 mu l volumes of serum with a diluent containing 1.0% v/v butan-l-ol; 0.66% Triton X-100; 0.01 mol l(-1) NH3, 0.0002 mol l(-1) (NH4)(2)H-2 EDTA and 0.002 mol l(-1) NH4H2PO4 enables ICP-MS to provide accurate and precise measurements of total selenium concentrations. Interferences from argon-adduct ions on selenium isotopes Se-77, Se-78 are eliminated and are considerably reduced at Se-82 by the presence in the diluent of butan-l-ol, The other reagents prevent blockage of the torch injector tube during prolonged, greater than or equal to 6 h, analytical runs, The detection limit (3s blank) is 0.02 mu mol l(-1) (1.5 mu g l(-1)) and within-run RSDs range from 3.4 to 7.5% at 0.3 mu mol l(-1), to 1.5 to 2.0% at 2.1 mu mol l(-1). Analyses of 12 sera from an external quality assessment program, of a commercially available reference serum material (Nycomed) and of in-house internal quality control sera gave excellent agreements with median/target concentrations over the range 0.3 to 3.3 mu mol l(-1). The ICP-MS data showed small, but acceptable, negative biasses at 1.0 mu mol l(-1) of: -3.8% and -5.0% at Se-77 and Se-78, respectively.