MC-ICP-MS measurement of δ^(34)S and Δ^(33)S in small amounts of dissolved sulfate
Abstract
Over the last decade, the use of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) has significantly lowered the detection limit of sulfur isotope analyses, albeit typically with decreased precision. Moreover, the presence of isobaric interferences for sulfur prevented accurate analysis of the minor isotopes ^(33)S and ^(36)S. In the present study, we report improved techniques for measuring sulfur isotopes on the MC-ICP-MS Neptune Plus (Thermo Fischer Scientific) using a heated spray chamber coupled to a desolvating membrane (Aridus, Cetac). Working at high mass resolution, we measured δ^(34)S values of natural samples with a typical reproducibility of 0.08–0.15‰ (2sd) on 5 to 40 nmol sulfur introduced into the instrument. We applied this method to two seawater profiles, using 25 μl of sample (700 nmol of sulfate). The average δ^(34)S_(VCDT) value is 20.97 ± 0.10‰ (2sd, n = 25). We show that the amount of sulfate required for an analysis can be decreased to 5 nmol. Because the plasma is sustained by Ar, measurement of ^(36)S is impossible at the current mass resolution due to the presence of ^(36)Ar^+, but a reproducibility of 0.1–0.3‰ (2sd) is achieved on the measurement of mass independent fractionations (Δ^(33)S). This is the first time such precision has been achieved on samples of this size.
Additional Information
© 2013 Elsevier B.V. Received 16 November 2012. Received in revised form 16 February 2013. Accepted 19 February 2013. Available online 5 March 2013. Editor: U. Brand. The authors would like to acknowledge Nathan Dalleska for precious help in using the IC, Eric Kort for helping with Allan variance analyses, Seth John for providing the seawater samples and Nivedita Thiagarajan for the coral sample. We also thank two anonymous reviewers for their comments and suggestions. This work was supported by the Camille and Henry Dreyfus Postdoctoral Program in Environmental Chemistry. The Adkins and Sessions groups are also deeply thanked for feedbacks and support. Thanks also to Vicky Rennie for being a motivated early user of this new method.Additional details
- Eprint ID
- 39716
- DOI
- 10.1016/j.chemgeo.2013.02.022
- Resolver ID
- CaltechAUTHORS:20130801-142621209
- Camille and Henry Dreyfus Foundation
- Created
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2013-08-01Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field
- Caltech groups
- Division of Geological and Planetary Sciences