Sulfur Isotope Studies in Solid Organics: A Protocol for Utilizing Heterogeneous Standards and Secondary Ion Mass Spectrometry

摘要

We present sulfur isotope compositions (~(34)S/~(32)S) for nine solid organics—six petroleum cokes and three solid bitumens—demonstrating a reliable method using secondary ion mass spectrometry (SUMS) for complex, inhomogeneous materials. The protocol uses a homogeneous working standard, a heterogeneous matrix standard, and statistical measures to identify outliers in the analyses. We demonstrate screening methods that minimize the impact of heterogeneities on the SIMS data, leading to a calibrated matrix correction that can facilitate analysis of sulfur isotope composition in solid organics. The thiophenlc sulfur and low H/C matrices of the selected materials are good surrogates for many solid organics. Furthermore, the approach is generally applicable to a wide range of materials and provides a means to obtain meaningful SIMS data when suitable homogeneous standards are unavailable.