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

We describe a fast, inexpensive, and safe method of direct S[O.sub.2] extraction from BaS[O.sub.4] for sulfur isotopic analysis by mass spectrometry. Only two reagents are used: (1) pure NAP[O.sub.3], which is mixed with BaS[O.sub.4] sample, and (2) Cu foil, from which reaction boats are manufactured. The extraction precedes in the Cu boat placed into a quartz tube connected to a vacuum line. The boat is heated to 650-700 [degrees] C while pure S[O.sub.2] produced is collected in a 'cold finger'. Reaction is complete in 7-10 min. We have proven by means of 18O-enriched BAS[O.sub.4] specimens that the oxygen isotopic composition of the S[O.sub.2] is totally controlled by 18O content in NAP[O.sub.3], when the weight ratio of the reagent to sample exceeds 6:1. The method described can be used for 'on-line' S[O.sub.2] preparation for isotopic analysis.