The use of ETV-ICP-MS for the determination of selenium in serum

Abstract

The development of a novel procedure for the accurate determination of selenium in serum using electrothermal vaporisation inductively coupled plasma mass spectrometry (ETV-ICP-MS) is described. The proposed method eliminates the need for a lengthy sample digestion procedure (a requirement with many methods for the analysis of biological samples), utilising a simple 1+19 dilution of the serum with 1% nitric acid. Many of the interferences normally associated with the determination of selenium by ICP-MS are successfully eliminated with careful optimisation of the ETV temperature program and modifier system. Analytical characteristics for ⁷⁴ Se, ⁷⁷ Se, ⁷⁸ Se and ⁸² Se are reported, including detection limits (3σ blank) of approximately 0.1 ng g ^–1 for ⁷⁷ Se and ⁸² Se. Short- and long-term reproducibility data between 4.7 and 4.9% and 3.2 and 3.8% (RSD) for ⁷⁷ Se and ⁸² Se, respectively, are shown. The accuracy of the method, which included Te as an internal standard, was demonstrated with the analysis of three internal quality control samples and the certified reference material NIST SRM 1598 (bovine serum). Results within 10% of the target value were achieved for three of the four isotopes studied, with slightly worse results for ⁷⁸ Se owing to the large interference from argon adduct ions on this isotope. Preliminary work involving the addition of nitrogen to the argon aerosol carrier gas was successful in reducing the ArAr interference at m/z 78.