Low-temperature thermal decomposition of sulfates to SO2 for on-line S-34/S-32 analysis

We describe a fast, inexpensive, and safe method of direct SO2 extraction f rom BaSO4 for sulfur isotopic analysis by mass spectrometry. Only two reage nts are used: (1) pure NaPO3, which is mixed with BaSO4 sample, and (2) Cu foil, from which reaction boats are manufactured. The extraction precedes i n the Cu boat placed into a quartz tube connected to a vacuum line. The boa t is heated to 650-700 degrees C while pure SO2 produced is collected in a "cold finger". Reaction is complete in 7-10 min. We have proven by means of O-18-enriched BaSO4 specimens that the oxygen isotopic composition of the SO2 is totally controlled by O-18 content in NaPO3, when the weight ratio o f the reagent to sample exceeds 6:1. The method described can be used for " on-line" SO2 preparation for isotopic analysis.