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COSMO: Double spike optimization for sample-limited analyses of isotopically anomalous materials

Marquez, Ren T. C. and Tissot, François L. H. (2022) COSMO: Double spike optimization for sample-limited analyses of isotopically anomalous materials. Chemical Geology, 612 . Art. No. 121095. ISSN 0009-2541. doi:10.1016/j.chemgeo.2022.121095.

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The double spike (DS) technique is the gold standard by which high-precision and high-accuracy mass-dependent isotope fractionations are quantified, and has played a critical role in the recent development of numerous non-traditional stable isotope systems. The democratization of the technique is in great part due to the availability of the so-called ‘DS toolbox’, a software suite that allows for the straightforward identification of optimal DS compositions. As new applications for DS measurements arise, some additional considerations must be taken into account in deciding on an optimal double spike. In particular, sample-limited investigations of combined mass-dependent and independent isotope effects (e.g., in Early Solar System materials) present an additional challenge in determining optimal spikes. Here, we describe the cosmo software package, which specifically addresses this upcoming need in cosmochemistry/isotope geochemistry to optimize DS measurements for small samples with mass-independent anomalies (e.g., nucleosynthetic anomalies, radiogenic ingrowth). These measurements are subject to additional errors from a complementary unspiked measurement, which is necessary to properly quantify mass-dependent isotope effects during the DS inversion. The software package addresses this additional complication by offering users the ability to (i) specify additional parameters relevant to practical sample-limited analyses (e.g., instrumental transmission efficiency, number of cycles of analyses), (ii) optimize how a sample is split between unspiked and spiked measurements, and (iii) identify the internal normalization scheme that leads to the lowest uncertainty on the mass-dependent fractionation factor, α, and/or the isotope anomalies, ε. These additional functionalities were designed to operate within the DS toolbox framework and expands its applicability to a wider array of samples (i.e., extraterrestrial samples) and measurement scenarios to push the limits of new and improved instrumentation.

Item Type:Article
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Marquez, Ren T. C.0000-0002-8317-9397
Tissot, François L. H.0000-0001-6622-2907
Additional Information:This work was supported by NASA grant 80NSSC21K1544 (PI: FLHT., FI: RTCM), NSF grants EAR-1824002 and MGG-2054892, a Packard Fellowship, a research award from the Heritage Medical Research Institute, and start-up funds provided by Caltech to FLHT. We thank B.L.A. Charlier and J. Hu for helpful and engaging discussions about the DS technique. We thank reviewers S. Galer, and J. Rudge, as well as well as editor D. Porcelli, for their constructive criticisms which helped improve the manuscript. Data availability. The code is open source and freely available online. The code used to generate the figures are also available and explained on the associated github repository ( CRediT authorship contribution statement. Ren T.C. Marquez: Conceptualization, Methodology, Software, Visualization, Writing-original-draft. François L.H. Tissot: Conceptualization, Methodology, Writing-review-editing. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Group:Division of Geological and Planetary Sciences, Heritage Medical Research Institute
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David and Lucile Packard FoundationUNSPECIFIED
Heritage Medical Research InstituteUNSPECIFIED
Record Number:CaltechAUTHORS:20221128-494241100.7
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:118052
Deposited By: Research Services Depository
Deposited On:06 Jan 2023 21:43
Last Modified:06 Jan 2023 21:44

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