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High-precision measurement of 36 SF 5 + signal using the MAT 253 Ultra isotope-ratio mass spectrometer
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  • Xiang Sun,
  • Fengtai Tong,
  • Yongbo Peng,
  • Huiming Bao
Xiang Sun
Nanjing University
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Fengtai Tong
Nanjing University

Corresponding Author:[email protected]

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Yongbo Peng
Nanjing University
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Huiming Bao
Nanjing University
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Rationale: The Δ 36S standard deviation (SD) measured in a conventional isotope-ratio mass spectrometer (IRMS) such as MAT 253 is at c.a. 0.1‰ to 0.3‰. At this precision, it is difficult to resolve the origin of non-mass-dependent sulfur (NMD-S) isotope fractionation in the tropospheric sulfate aerosol and in Martian meteorites or small deviations from the canonical mass-dependent fractionation laws. Interfering ions (originated from fluorination and/or mass spectrometer ion source itself) with m/z at 131 of 36SF 5 + by the community as the cause of the poor precision, but the exact ion species has not been identified or confirmed. Methods: Here we examined the potential interfering ions by using the Thermo Scientific MAT 253 Ultra, a high-resolution (mass resolving powers up to 40,000) stable isotope-ratio mass spectrometer, to measure the SF 6 working gas and SF 6 gases converted from IAEA-S1 Ag 2S reference materials via a fluorination system. Results: We found that there is a resolvable peak to the right of the 36SF 5 + peak for both the SF 6 working gas and SF 6 generated by the fluorination system. The peak is identified as the 12C 3F 5 + ion, generated inside the instrument during the ionization process. By minimizing the presence of carbon-bearing compounds (e.g., organic matter in sample or helium gas, glue or o-ring in sample tubes, or carbon-bearing gases inside the mass spectrometer), we were able to achieve a Δ 36S SD of 0.046‰ (n=8) for SF 6 zero-enrichment and 0.069‰ (n=8) for overall measurement start from sliver sulfide IAEA-S1. Conclusions: Minimizing the presence of carbon-bearing compounds and avoiding the interfering signals from 36SF 5 + via MAT 253 Ultra high‐resolution isotope-ratio mass spectrometer, we can improve Δ 36S measurement precision by 2 to 5 folds, which helps to open new territories for research using quadruple sulfur isotope composition.
23 Feb 2024Submitted to Rapid Communications in Mass Spectrometry
23 Feb 2024Assigned to Editor
23 Feb 2024Submission Checks Completed
02 Mar 2024Reviewer(s) Assigned
31 Mar 2024Review(s) Completed, Editorial Evaluation Pending