Development and characterization of a new in-house reference material for stable carbon and oxygen isotopes analyses

The precision and accuracy of an isotope ratio mass spectrometry (IRMS) laboratory and the quality of its scientific output directly depend on the quality of the reference materials used for calibration. However, the specification and characterization of the in-house reference material and analytica...

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Bibliographic Details
Published in:Journal of analytical atomic spectrometry 2021-06, Vol.36 (6), p.1125-1134
Main Authors: Crivellari, Stefano, Viana, Patrícia Junia, Campos, Marília de Carvalho, Kuhnert, Henning, Machado Lopes, Alyne Barros, Cruz, Francisco William da, Chiessi, Cristiano Mazur
Format: Article
Language:English
Subjects:
Calcite
Calcium carbonate
Carbon
Grain size
Homogeneity
Isotope ratios
Isotopes
Laboratories
Mass spectrometry
Mathematical analysis
Mineralogy
Normalizing
Oxygen isotopes
Paleoceanography
Paleoclimatology
Reference materials
X-ray fluorescence
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Summary:The precision and accuracy of an isotope ratio mass spectrometry (IRMS) laboratory and the quality of its scientific output directly depend on the quality of the reference materials used for calibration. However, the specification and characterization of the in-house reference material and analytical details of the laboratory routine are rarely published or accompanied in the scientific studies that rely on IRMS measurements. Here we describe the development of a new in-house laboratory reference material (SHP2L) used for normalizing measurements of carbon and oxygen stable isotopes ( δ 13 C and δ 18 O) of carbonate material at the newly formed Paleoceanography and Paleoclimatology Laboratory (P2L). The analytical setup consists in a Thermo™ MAT253 coupled to a Thermo™ Kiel IV carbonate device. The equipment is stable in the long term (precision better than 0.1‰ over a two-months period) and ensures analytical precision (sample-to-sample, 1 σ ) better than 0.04‰ for δ 13 C and 0.07‰ for δ 18 O, down to masses of 30 μg. The material chosen for the production of the SHP2L is a calcium carbonate plate (about 800 cm 3 to 2.1 kg) from the German Jurassic Solnhofen Formation. The isotopic homogeneity was assessed by taking 25 regularly spaced samples from both sides of the plate. The standard deviation of these samples were less than 0.11‰ for both δ 13 C and δ 18 O. The plate was then fragmented, ground and sieved to isolate the 63-124 μm grain-size fraction. The chemical and mineralogical quality of the SHP2L was established by X-ray fluorescence and diffraction respectively, which show predominantly calcium carbonate, with negligible amounts of other constituents in purely calcite mineralogical phase. Batches of ca. 50 samples from the 63-124 μm fraction were analyzed for δ 13 C and δ 18 O in three laboratories. Established SHP2L isotopic composition is −0.766 ± 0.042‰ for δ 13 C e −5.741 ± 0.064‰ for δ 18 O. The SHP2L proved to be a homogeneous reference material for δ 13 C and δ 18 O stable isotopes analyses. The methodological template for production of a carbonate working standard is illustrated herein. The SHP2L is available for distribution upon request to the first author. We describe the characterization of a newly produced reference material, the SHP2L. It is made of virtually pure calcite and of uniform isotopic composition, suitable for stable carbon and oxygen isotope analyses.
ISSN:0267-9477
1364-5544
DOI:10.1039/d1ja00030f