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

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's t-test, P < 0.05); the concentration ratio of acid digestion to alkaline fusion was 0.85 on average. When the total Re content was higher than 0.2 ng g−1, the acid digestion method could dissolve about 80% of the sample Re. Although the acid digestion method is unable to dissolve all Re in the sample, however, the Re discharged to soils could be more extractable than the Re in the dissolution-resistant part; thus, the acid digestion method could be useful for obtaining Re levels in soil samples.