Single reaction chamber microwave digestion coupled with ICP-MS for the determination of ultra-trace mercury in rocks.

Abstract

In this study, a method for rock digestion using a single reaction chamber (SRC) microwave system was established. Nitric acid (HNO3) and hydrofluoric acid (HF) were used as digestion agents, and the determination of mercury (Hg) in rocks was performed by inductively coupled plasma mass spectrometry (ICP-MS). The optimal conditions for the SRC microwave system were achieved at 260 °C and 70 bar, with a mixture of 3 mL of 65-68 wt% HNO3 and 1 mL of 49 wt% HF when the sample weight is in the range of 0.025-0.05 g. The method quantitation limit (MQL) was determined to be 0.0016 mg kg-1. Measurement accuracy was evaluated using five Chinese nationally certified reference materials, demonstrating good consistency between measurement results and certified values. The method was applied to two rock samples, resulting in a recovery rate ranging from 105% to 109%. This method exhibits high sensitivity, stability, and low acid consumption. Importantly, it provides a reliable and efficient determination method for Hg in rocks, which is of great significance in geochemical analysis.