Microwave digestion in a 6 mL HNO3 and 0.5 mL HBF4 acid digestion mixture can achieve total solubilization of Sb in solid samples. Thirty minutes at 200 degrees C with 100 mmol L-1 of oxalic acid were suitable conditions for fast and efficient microwave extraction to obtain a good extraction yield. However, Sb(III) stabilization was strongly inhibited; thus, the mixture of 100 mmol L-1 + 20 mmol L-1 of ascorbic acid was the best for Sb solubilization and Sb(III) stabilization. A total of 1.8 +/- 0.1 mu g g(-1) of Sb was quantified in the volcanic ash from the first eruption. The Sb concentrations in the sediments were 3 times higher than the Sb concentrations in the sediments from the reference zone. In the extracts of the volcanic ash and sediment, Sb(III) was the most abundant species, accounting for 70 to 97% of the total Sb found in the extracts. The results suggest that most of the Sb thrown from the Chaiten Volcano accumulated in the sediments at the mouths of the Yelcho and Chaiten Rivers, mainly in the form of Sb(III). (C) 2016 Elsevier B.V. All rights reserved.