Stable Isotope Analysis of Intact Oxyanions Using Electrospray Quadrupole-Orbitrap Mass Spectrometry

Neubauer, Cajetan and Crémière, Antoine and Wang, Xingchen T. and Thiagarajan, Nivedita and Sessions, Alex L. and Adkins, Jess F. and Dalleska, Nathan F. and Turchyn, Alexandra V. and Clegg, Josephine A. and Moradian, Annie and Sweredoski, Michael J. and Garbis, Spiros D. and Eiler, John M. (2020) Stable Isotope Analysis of Intact Oxyanions Using Electrospray Quadrupole-Orbitrap Mass Spectrometry. Analytical Chemistry, 92 (4). pp. 3077-3085. ISSN 0003-2700 DOI

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The stable isotopes of sulfate, nitrate, and phosphate are frequently used to study geobiological processes of the atmosphere, ocean, as well as land. Conventionally, the isotopes of these and other oxyanions are measured by isotope-ratio sector mass spectrometers after conversion into gases. Such methods are prone to various limitations on sensitivity, sample throughput, or precision. In addition, there is no general tool that can analyze several oxyanions or all the chemical elements they contain. Here, we describe a new approach that can potentially overcome some of these limitations based on electrospray hyphenated with Quadrupole Orbitrap mass spectrometry. This technique yields an average accuracy of 1–2‰ for sulfate δ34S and δ18O and nitrate δ15N and δ18O, based on in-house and international standards. Less abundant variants such as δ17O, δ33S, and δ36S, and the 34S–18O “clumped” sulfate can be quantified simultaneously. The observed precision of isotope ratios is limited by the number of ions counted. The counting of rare ions can be accelerated by removing abundant ions with the quadrupole mass filter. Electrospray mass spectrometry (ESMS) exhibits high-throughput and sufficient sensitivity. For example, less than 1 nmol sulfate is required to determine 18O/34S ratios with 0.2‰ precision within minutes. A purification step is recommended for environmental samples as our proposed technique is susceptible to matrix effects. Building upon these initial provisions, new features of the isotopic anatomy of mineral ions can now be explored with ESMS instruments that are increasingly available to bioanalytical laboratories.

Item Type: Article
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Analytical Chemistry
Volume: 92
Page Range: pp. 3077-3085
Identification Number:
Depositing User: Sarah Humbert
Date Deposited: 03 Mar 2020 10:35
Last Modified: 03 Mar 2020 10:35

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