Simple Method for the Accurate Determination of Selenium in Serum by Using Inductively Coupled Plasma Mass Spectrometry

Abstract

A simple 1+15 dilution of 200 µl 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)₂H₂ 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 ⁷⁷Se, ⁷⁸Se are eliminated and are considerably reduced at ⁸²Se by the presence in the diluent of butan-l-ol. The other reagents prevent blockage of the torch injector tube during prolonged, ≥6 h, analytical runs. The detection limit (3s blank) is 0.02 µmol l^-1 (1.5 µg l^-1) and within-run RSDs range from 3.4 to 7.5% at 0.3 µmol l^-1, to 1.5 to 2.0% at 2.1 µmol 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 µmol l^-1. The ICP-MS data showed small, but acceptable, negative biasses at 1.0 µmol l^-1 of: -3.8% and -5.0% at ⁷⁷Se and ⁷⁸Se, respectively.

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