A practical method for the determination of total selenium in environmental samples using isotope dilution-hydride generation-inductively coupled plasma-mass spectrometry

A safe, practical, and accurate method for the determination of selenium (Se) in range of environmental samples was developed. Small sample masses, 5–20 mg, were amended with ⁸²Se enriched isotope for the isotope dilution (ID), preceding a multi-step wet digestion with nitric acid (HNO₃) and hydrogen peroxide (H₂O₂). Samples were incubated in an autoclave for 3 h at 20 psi and 126°C. Digestates were subsequently reduced with concentrated hydrochloric acid to Se(IV) the most favorable valence for hydride generation (HG). The solutions were then analyzed on an ICP-MS equipped with Flow Injection system (FIAS-400). Polyatomic, isobaric, and background interferences were removed through the use of HG and ID with an ⁸²Se enriched isotope spike. Recoveries for certified reference materials were determined and averaged 96% for biological tissues (NRCC DOLT3, DOLT4, DORM2, TORT2, and TORT3, and NIST 2976) and 108% for estuarine sediment (NRCC PACS2) with an average coefficient of variation for replicate measurements of ∼ 3.5%. Limit of detection was 0.13 ng Se g⁻¹ dry weight or 0.19 ng Se L⁻¹. This method can be broadly applied to biological tissues, sediments, suspended particulates, and water samples with minimal modifications making this method highly useful for assessing the ecotoxicology of total Se in aquatic ecosystems.