An Improved Procedure for the Determination of Trace Elements in Silicate Rocks Using NH4HF2 Digestion

Knowledge of the elemental composition of geological samples is of high significance to research in Earth science. For whole‐rock elemental determination, complete sample digestion is essential to obtain bias‐free measurement results. In recent years, NH 4 HF 2 digestion has been proposed for geological sample dissolution; however, this requires 3 h of sample evaporation and 6 h of re‐dissolution of residues. In this study a PTFE beaker, which can withstand 300 °C, was designed to increase the evaporation temperature, reducing the evaporation time to 15 min. Further investigations found that the insoluble fluoride residues formed during the high‐temperature evaporation stage significantly influenced the recoveries of Sc, Y, rare earth elements and Th. Among the tested strategies to suppress the formation of fluorides, the microwave heating method was the most efficient and robust. The optimised NH 4 HF 2 digestion shortened the sample evaporation and re‐dissolution times from 9 h to 21 min, significantly reducing the time consumed for sample evaporation by a factor of ~ 26. A suite of silicate rock reference materials was analysed. The results for most elements were in agreement with reference values with a measurement bias of < 10%.