General High-Pressure Closed Acidic Decomposition Method of Rock Samples for Trace Element Determination Using Inductively Coupled Plasma Mass Spectrometry

Complete decomposition is an essential prerequisite for accurate trace element quantification in geological samples. This work presents a general high-pressure closed digestion approach for rock samples from basic to acidic rocks by inductively coupled plasma mass spectrometry. Using HNO3−HF mixed system, different geological reference materials have been investigated for trace element determination, with acid ratio, decomposition time, digestion temperature, sample mass and reagent amount discussed in detail. In brief, 2.0 mL of HNO3−HF with the ratio of 1 : 1 and a digestion time of 12 h at 185°C in high-pressure sealed bomb are optimal for 50 mg rock sample decomposition. With relative errors under 10%, the analytical results of W-2a, BCR-2, GSP-2, AGV-2 and GSR-1 agree well with certified values. This proposed high-pressure sealed digestion method is characterized with less acid consumption, complete digestion and less damage for digestion process, well meeting the requirements for large sample throughput in geological laboratory.