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Volatilisation of Trace Elements During Evaporation to Dryness of HF‐Dissolved Silicates (BHVO‐2, AGV‐1, BIR‐1, UB‐N): Open‐ Versus Closed‐System Conditions

This work characterises the volatilisation of trace elements during evaporation to dryness of HF‐dissolved silicate rock reference materials (BHVO‐2, AGV‐1, BIR‐1, UB‐N). In open‐system conditions, sublimation at 80 °C remained small (≤ 3%) for most elements with the exception of boron. Conversely, during closed‐system evaporation in a PTFE elbow, volatilisation loss could exceed 3% for Te, Au, Se, Ru, B, Re, As, V and Ge; 100 μg g−1 for Pt, Cd, Ag, Mo and Ti; and 10 μg g−1 for many refractory elements including Nb, Hf, U and Yb. Higher volatilisation loss in the closed‐system results from the higher vapour pressure of HF that allows for the formation of highly fluorinated species with lower sublimation temperature, or unstable species such as rare earth tetrafluorides for which sublimation competes with thermal decomposition. Increasing the temperature from 50 to 100 °C promotes the formation and sublimation of highly fluorinated species (VF5, GeF4, SeF6). Conversely, some refractory elements (Hf, Zr, Yb, U, Cu, Zn, Rb, Ba and Sr) seem to preferentially sublimate at 50 °C possibly through the formation of hydrated fluorides. Our results indicate that closed‐system evaporation must be used with caution for quantitative analyses.