Dataset Information
USGS44, a new high-purity calcium carbonate reference material for ?13 C measurements.
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ABSTRACT: Rationale
The stable carbon isotopic (?13 C) reference material (RM) LSVEC Li2 CO3 has been found to be unsuitable for ?13 C standardization work because its ?13 C value increases with exposure to atmospheric CO2 . A new CaCO3 RM, USGS44, has been prepared to alleviate this situation.Methods
USGS44 was prepared from 8?kg of Merck high-purity CaCO3 . Two sets of ?13 C values of USGS44 were determined. The first set of values was determined by online combustion, continuous-flow (CF) isotope-ratio mass spectrometry (IRMS) of NBS 19 CaCO3 (?13 CVPDB ?=?+1.95 milliurey (mUr) exactly, where mUr?=?0.001?=?1‰), and LSVEC Li2 CO3 (?13 CVPDB ?=?-46.6 mUr exactly), and normalized to the two-anchor ?13 CVPDB-LSVEC isotope-delta scale. The second set of values was obtained by dual-inlet (DI)-IRMS of CO2 evolved by reaction of H3 PO4 with carbonates, corrected for cross contamination, and normalized to the single-anchor ?13 CVPDB scale.Results
USGS44 is stable and isotopically homogeneous to within 0.02?mUr in 100-?g amounts. It has a ?13 CVPDB-LSVEC value of -42.21?±?0.05?mUr. Single-anchor ?13 CVPDB values of -42.08?±?0.01 and -41.99?±?0.02?mUr were determined by DI-IRMS with corrections for cross contamination.Conclusions
The new high-purity, well-homogenized calcium carbonate isotopic reference material USGS44 is stable and has a ?13 CVPDB-LSVEC value of -42.21?±?0.05?mUr for both EA/IRMS and DI-IRMS measurements. As a carbonate relatively depleted in 13 C, it is intended for daily use as a secondary isotopic reference material to normalize stable carbon isotope delta measurements to the ?13 CVPDB-LSVEC scale. It is useful in quantifying drift with time, determining mass-dependent isotopic fractionation (linearity correction), and adjusting isotope-ratio-scale contraction. Due to its fine grain size (smaller than 63??m), it is not suitable as a ?18 O reference material. A ?13 CVPDB-LSVEC value of -29.99?±?0.05?mUr was determined for NBS 22 oil.
SUBMITTER: Qi H
PROVIDER: S-EPMC7816275 | biostudies-literature | 2021 Feb
REPOSITORIES: biostudies-literature
Publications
USGS44, a new high-purity calcium carbonate reference material for δ<sup>13</sup> C measurements.
Rapid communications in mass spectrometry : RCM 20210201 4
<h4>Rationale</h4>The stable carbon isotopic (δ<sup>13</sup> C) reference material (RM) LSVEC Li<sub>2</sub> CO<sub>3</sub> has been found to be unsuitable for δ<sup>13</sup> C standardization work because its δ<sup>13</sup> C value increases with exposure to atmospheric CO<sub>2</sub> . A new CaCO<sub>3</sub> RM, USGS44, has been prepared to alleviate this situation.<h4>Methods</h4>USGS44 was prepared from 8 kg of Merck high-purity CaCO<sub>3</sub> . Two sets of δ<sup>13</sup> C values of USGS4 ...[more]