Simultaneous Quantification of Critical Mineral Elements Gallium, Indium, Germanium, Selenium, and Tellurium in Soil and Stream Sediment by Inductively Coupled Plasma Tandem Mass Spectrometry

Gallium, indium, germanium, selenium and tellurium are extremely scarce and widely dispersed in Earth’s crust, which have been included in the critical mineral list due to their extensive application in modern clean energy transitions. Traditional analytical methods are limited by their weak mass spectrometric response and severe interference (especially selenium), requiring the use of two techniques, ICP-MS and HG-AFS, which cannot achieve simultaneous determination of the same sample after one dissolution. An open vessel digestion employed with HF-HNO₃-HClO₄ to avoid the loss of Ge and Se while ensuring complete sample digestion. Isopropanol (2%, V/V) was selected as a sensitizer to improve the MS response of ⁸⁰Se and ¹²⁸Te by 2.75 and 2.32 folds. The severe MS interference of ⁸⁰Se was eliminated by mass-shift mode using oxygen as the reaction gas in ICP-MS/MS and the signal-to-noise ratio of ⁸⁰Se reaches 58.20. A simultaneous determination method of Ga, In, Ge, Se and Te by ICP-MS/MS was established in this study, the detection limits of this method were 0.002-0.060μg/g, and the ΔlgC of six certified reference materials were all within ±0.05, while RSD＜5%. The established method of this study solves the disadvantages of easy volatilization loss of Ge and Se during digestion, the poor MS response of Se and Te, and the severe interference of Se in single-quadrupole ICP-MS which requires aqua regia semi-digestion. This method archives the simultaneous determination of five critical mineral elements Ga, In, Ge, Te and Se in typical geological samples (soil and stream sediment) in a single run.