Analysis of multiple sulfur isotopes using a Curie-point Pyrolyzer and an automated sample preparation system

Sulfur is a versatile element with various redox states, which makes it a key component in both geological and biological worlds. Geobiological reactions involving sulfur often lead to isotope fractionation of its four isotopes, making their relative abundance as a major clue to understand the past and the current sulfur cycle. With the advent of a high-resolution isotope ratio mass spectrometer (IRMS), analyzing all four isotopes of sulfur became possible using SF6 as a sample gas. However, such method has never been conducted in South Korea due to its complexity and hazardousness. Here, we show an instant synthesis and analysis of SF6 using a Curie-point Pyrolyzer and an IRMS MAT 253 Plus installed in the School of Earth and Environmental Sciences at Seoul National University. CoF3 , which is less hazardous than F2 , was used as a fluorinating agent. In addition, an automated gas line for purifying SF6 was constructed and connected between the pyrolyzer and MAT 253 Plus. While the SF6 yield rate is relatively lower than that of the traditional method, our analysis with IAEA standards shows sufficient reproducibility (2 sigma) of 0.33%0, 0.022%0, and 0.24%0 for delta 34S, Delta 33S, and Delta 36S, respectively. Our results also agree well with other reported values obtained from similar SF6 methods within errors, but measuring SF6 below 1 mu mol generally decreases the accuracy of the results. Overall, our new SF6 analysis methodology can allow in-depth analysis in South Korea not only on the deviations of sulfur isotope ratios from their mass-dependent relationships by a few permil, but also on subtle variations in the minor sulfur isotope ratios.