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Clumped isotope measurements of small carbonate samples using a high‐efficiency dual‐reservoir technique
Author(s) -
Petersen Sierra V.,
Schrag Daniel P.
Publication year - 2014
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.7022
Subject(s) - carbonate , isotopologue , chemistry , isotope , mass spectrometry , analytical chemistry (journal) , mineralogy , inlet , geology , chromatography , oceanography , physics , organic chemistry , quantum mechanics , molecule
RATIONALE The measurement of multiply substituted isotopologues of CO 2 derived from carbonate has allowed the reconstruction of paleotemperatures from a single phase (CaCO 3 ), circumventing uncertainty inherent in other isotopic paleothermometers. Traditional analytical techniques require relatively large amounts of carbonate (3–8 mg per replicate), which limits the applicability of the clumped isotope proxy to certain geological materials such as marine microfossils, commonly used for paleoclimate reconstructions. METHODS Clumped isotope ratio measurements of small samples were made on a new, high‐efficiency, dual‐reservoir sample‐preparation inlet system attached to a Thermo‐Finnigan MAT 253 mass spectrometer. Sample gas produced on the inlet is introduced from a 10 mL reservoir directly into the source via a capillary. Reference gas fills an identical 10 mL reservoir installed between the reference bellows and the capillary. The gas pressures in the two reservoirs are initially balanced, and are allowed to decrease together over the run. RESULTS Carbonate samples from 1 mg to 2.6 mg produced Δ 47 values equivalent to those from the traditional two‐bellows method with identical single‐sample precision (1 SE = 0.005–0.015‰) and external standard error (SE = 0.006–0.015‰, n = 4–6). The size of sample needed to achieve good precision is controlled by the sensitivity of the mass spectrometer and the size of the fixed reservoirs and adjacent U‐trap installed on our inlet. CONCLUSIONS The high‐precision clumped isotope measurements of small aliquots of carbonate obtained in this method allows for the application of this proxy to a wider range of geological sample materials, such as marine microfossils, that until now have been nearly impossible to analyze given sample size limitation. Copyright © 2014 John Wiley & Sons, Ltd.