Rapid quantification and isotopic analysis of dissolved sulfur species

Derek A. Smith, Alex L. Sessions, Katherine S. Dawson, Nathan Dalleska, Victoria J. Orphan

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Rationale: Dissolved sulfur species are of significant interest, both as important substrates for microbial activities and as key intermediaries in biogeochemical cycles. Species of intermediate oxidation state such as sulfite, thiosulfate, and thiols are of particular interest but are notoriously difficult to analyze, because of low concentrations and rapid oxidation during storage and analysis. Methods: Dissolved sulfur species are reacted with monobromobimane which yields a fluorescent bimane derivative that is stable to oxidation. Separation by Ultra-Performance Liquid Chromatography (UPLC) on a C18 column yields baseline resolution of analytes in under 5 min. Fluorescence detection (380 nm excitation, 480 nm emission) provides highly selective and sensitive quantitation, and Time-of-Flight Mass Spectrometry (TOF-MS) is used to quantify isotopic abundance, providing the ability to detect stable isotope tracers (either 33S or 34S). Results: Sulfite, thiosulfate, methanethiol, and bisulfide were quantified with on-column detection limits of picomoles (μM concentrations). Other sulfur species with unshared electrons are also amenable to analysis. TOF-MS detection of 34S enrichment was accurate and precise to within 0.6% (relative) when sample and standard had similar isotope ratios, and was able to detect enrichments as small as 0.01 atom%. Accuracy was validated by comparison to isotope-ratio mass spectrometry. Four example applications are provided to demonstrate the utility of this method. Conclusions: Derivatization of aqueous sulfur species with bromobimane is easily accomplished in the field, and protects analytes from oxidation during storage. UPLC separation with fluorescence detection provides low-μM detection limits. Using high-resolution TOF-MS, accurate detection of as little as 0.01% 34S label incorporation into multiple species is feasible. This provides a useful new analytical window into microbial sulfur cycling.

Original languageEnglish (US)
Pages (from-to)791-803
Number of pages13
JournalRapid Communications in Mass Spectrometry
Volume31
Issue number9
DOIs
StatePublished - May 15 2017
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry

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