Improved thermal decomposition of sulfates to SO ₂ and mass spectrometric determination of δ ³⁴ S of IAEA SO‐5, IAEA SO‐6 and NBS‐127 sulfate standards

We describe a significant improvement to our low‐temperature thermal decomposition of sulfates to SO 2 for isotopic analysis (Halas S, Szaran J. Anal. Chem. 1999; 71: 3254) that has led to better reproducibility and efficiency of measurements. In the present approach we use a mixture of two reagents, NaPO 3 + V 2 O 5 , mixed in a weight ratio of 3:5. The addition of V 2 O 5 prevents overboiling of NaPO 3 at temperatures, T, increased to 800 °C. Using this modified method we obtained the following δ 34 S values (in ‰): +21.17 ± 0.12 for NBS‐127, +0.15 ± 0.06 for IAEA SO‐5, and −34.12 ± 0.11 for IAEA SO‐6.