Comparison of alkaline fusion and acid digestion methods for the determination of rhenium in rock and soil samples by ICP-MS

A simple acid digestion method was studied in order to analyze many samples at once to understand Re behavior in the terrestrial environment, because, under normal laboratory conditions, digestion methods generally used, such as Carius tube digestions, Teflon vessel digestions and alkaline fusions, can handle only a small number of samples at one time to ensure complete sample digestion. In this study, the Re results for reference materials (RMs) obtained by the acid digestion method were compared with those by the alkaline fusion digestion method to get applicability of the acid digestion method for Re determination in soil by inductively coupled plasma mass spectrometry. Alkaline fusion was chosen for the comparison because it is known to have the highest capability to dissolve Re in geological materials among digestion methods.The average total Re recoveries measured using the 185Re spike for RMs, such as rock, soil and sediment, were 90.6+/-4.0% for alkaline fusion and 92.2+/-7.3% for acid digestion, showing no differences between them. However, Re results obtained by the acid digestion method were usually slightly lower than those by the alkaline fusion (Student\u27s t-test, p