Revised δ34S reference values for IAEA sulfur isotope reference materials S-2 and S-3†

Revised δ34S reference values with associated expanded uncertainties (95% confidence interval (C.I.)) are presented for the sulfur isotope reference materials IAEA-S-2 (22.62 ± 0.16‰) and IAEA-S-3 (−32.49 ± 0.16‰). These revised values are determined using two relative-difference measurement techniques, gas source isotope ratio mass spectrometry (GIRMS) and double-spike multi-collector thermal ionization mass spectrometry (MC-TIMS). Gas analyses have traditionally been considered the most robust for relative isotopic difference measurements of sulfur. The double-spike MC-TIMS technique provides an independent method for value-assignment validation and produces revised values that are both unbiased and more precise than previous value assignments. Unbiased δ34S values are required to anchor the positive and negative end members of the sulfur delta (δ) scale because they are the basis for reporting both δ34S values and the derived mass-independent Δ33S and Δ36S values. Published in 2009 by John Wiley & Sons, Ltd.