Determination of ultra-trace rare earth elements in olivine by laser ablation-sector field-inductively coupled plasma-mass spectrometry

Rare earth elements (REEs) are important geochemical tracers in multiple fields of geochemistry. In this study, we develop a method for precise determination of olivine Eu/Eu* and REE concentrations (down to sub ng g −1 ) using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Using a Thermo Element XR SF-ICP-MS, we demonstrated that the Jet + H cone combination with the guard electrode under Ar-N 2 plasma (a small amount of N 2 added into carrier gas flow) conditions provides the optimal conditions for measuring 147 Sm, 153 Eu, and 158 Gd. Although the Jet + X cone combination could achieve the highest sensitivity, the usage of the X skimmer cone led to an extremely high oxide formation (ThO + /Th + >30%) and severe inter-element fractionation. Under optimized laser parameters (spot size: 160 μm, ablation frequency: 15 Hz, and energy density: 8 J cm −2 ) and ICP-MS conditions, detection limits of