Comparison of no gas and He/H2 cell modes used for reduction of isobaric interferences in selenium speciation by ion chromatography with inductively coupled plasma mass spectrometry

Inductively coupled plasma mass spectrometry (ICP-MS) used for the detection of most common selenium isotopes ⁷⁸Se (23.8%, abundance) and ⁸⁰Se (49.6%, abundance) is interfered in the presence of ³⁸Ar⁴⁰Ar⁺ and ⁴⁰Ar⁴⁰Ar⁺ in argon (Ar) gas. To address this issue, ICP-MS with an octopole reaction system (ORS) was explored for the detection of selenite and selenate, which was separated by anion-exchange chromatography. Results indicate that it was possible to detect ⁷⁸Se using no collusion gas, while to detect ⁸⁰Se a H₂ as the collusion/reaction gas was recommended since the background and noise were significantly reduced using H₂ as the gas. The selenium speciation interested was separated on a new column (G3154/101A, Agilent technologies) within 5 min using a mobile phase containing 10 mM NH₄H₂PO₄ and 20 mM NH₄NO₃ at pH 6.5. Linear plots were obtained in a concentration range of 1–200 μg/L with detection limits less than of 0.4 μg/L for ⁸⁰Se (IV) and 0.6 μg/L for ⁸⁰Se (VI) using H₂ as the reaction gas. Finally, the proposed method was used in the determination of selenium in water and soil.