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Experimental confirmation of isotope fractionation in thiomolybdates using ion chromatographic separation and detection by multi-collector ICPMS

Title data

Kerl, Carolin F. ; Lohmayer, Regina ; Bura-Nakić, Elvira ; Vance, Derek ; Planer-Friedrich, Britta:
Experimental confirmation of isotope fractionation in thiomolybdates using ion chromatographic separation and detection by multi-collector ICPMS.
In: Analytical Chemistry. Vol. 89 (2017) Issue 5 . - pp. 3123-3129.
ISSN 1520-6882
DOI: https://doi.org/10.1021/acs.analchem.6b04898

Abstract in another language

Molybdenum isotopes (98Mo/95Mo) are a sediment paleo proxy for the redox state of the ancient ocean. Under sulfidic conditions, no fractionation between seawater and sediment should be observed if molybdate (MoO42-) is quantitatively transformed to tetrathiomolybdate (MoS42-) and precipitated. However, quantum mechanical calculations previously suggested that incomplete sulfidation could be associated with substantial fractionation. To experimentally confirm isotope fractionation in thiomolybdates, a new approach for determination of isotope ratios of individual thiomolybdate species was developed that uses analytical chromatography (HPLC-UV) to separate individual thiomolybdates, collecting each peak and analyzing isotope ratios with multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Using commercially available MoO42- and MoS42- standards, the method was evaluated and excellent reproducibility and accuracy were obtained. For species with longer retention times, complete chromatographic peaks had to be collected to avoid isotope fractionation within peaks. Isotope fractionation during formation of thiomolybdates could be experimentally proven for the first time in the reaction of MoO42- with 20-fold or 50-fold excess of sulfide. The previously calculated isotope fractionation for MoS42- was confirmed and the result for MoO2S22- was in the predicted range. Isotopic fractionation during MoS42- transformation with pressurized air was dominated by kinetic fractionation. Further optimization and online-coupling of the HPLC-MC-ICP-MS approach for determination of low concentrations in natural samples will greatly help to obtain more accurate species-selective isotope information.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER139532
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Professorship Environmental Geochemistry Group
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Professorship Environmental Geochemistry Group > Professorship Environmental Geochemistry - Univ.-Prof. Dr. Britta Planer-Friedrich
Research Institutions
Research Institutions > Research Centres
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 08 Jan 2018 13:30
Last Modified: 26 Sep 2019 05:52
URI: https://eref.uni-bayreuth.de/id/eprint/41206