The effect of sulfate‐δ¹⁸O upon on‐line sulfate‐δ³⁴S analysis, and implications for measurements of δ³³S and Δ³³S

Abstract

On-line delta34S analysis of sulfate using an elemental analyzer has a number of advantages vs. conventional off-line techniques, such as ease of operation, rapidity, and the requirement for small amounts of material. Although the analyses are performed by converting sulfate into SO2 gas, the effect of sulfate-delta18O composition upon the SO2-delta18O composition and the value of delta66 during elemental analysis, and ultimately the calculated sulfate-delta34S composition, has rarely been addressed. Three BaSO4 samples were prepared with known identical delta34S compositions, but with a wide range of delta18O compositions. delta18O values were shown to range over 40 per thousand, but conventional on-line delta34S analyses verified that the sulfate-delta34S compositions were identical. These results indicate that conventional on-line analysis of sulfate-delta34S is unaffected by the value of sulfate-delta18O, and suggest that sulfide-delta34S standards can be used to calibrate sulfate-delta34S analyses (and vice versa). Moreover, these results suggest that it may be possible to use on-line sulfur isotope analysis of SO2 to measure delta33S and Delta33S in addition to delta34S, as a faster and safer alternative to the SF6 technique currently utilized, and hence promote further study of mass-independent sulfur isotope fractionation effects.

Correction of mass spectrometric isotope ratio measurements for isobaric isotopologues of O2, CO, CO2, N2O and SO2

“…If higher accuracy is required, some form of Eqn. (16) in Westley et al, 18 with at least the parameters a 31 and b 31 , needs to be used and the data reduction is best carried out using isotopocule and isotope ratios rather than d and z values.…”

“…In fact, previous treatments have ignored the other terms completely. 16,[53][54][55][56] In principle, Eqns. (65) and (67) together with Eqns.…”

Synthesis of Hexasaccharide Fragments of Pectin

“…The same arguments with respect to the non‐necessity of absolute isotope ratios apply to the other species. Partial and/or approximate solutions have been reported for CO14 and SO 2 15, 16. We also suggest experiments where the required correction coefficients can be measured using conventional isotope ratio mass spectrometers.…”

“…Clearly, the major correction from 66 δ to 34 δ is due to the contribution of 32 S 18 O 16 O + ions ( 18 δ term). In fact, previous treatments have ignored the other terms completely 16, 53–56. In principle, Eqns.…”

“…Alternatively, the oxygen atoms of the SO 2 sample and the reference material could be exchanged with a large reservoir or could be produced by reaction of a reduced sulphur species with the same O 2 gas, so that their oxygen isotope ratios are the same ( 17 δ = 18 δ = 0). In this case, 33 δ and 34 δ can be derived from 65 δ and 66 δ measurements alone:16, 53 …”