1. Preparation of high-precision CO2 with known triple oxygen isotope for oxygen isotope analysis.
- Author
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Sha, Lijuan, Mahata, Sasadhar, Duan, Pengzhen, Zong, Baoyun, Ning, Youfeng, Zhang, Pu, Wang, Jian, Cai, Yanjun, and Cheng, Hai
- Subjects
ISOTOPIC analysis ,OXYGEN isotopes ,ISOTOPIC fractionation ,KINETIC isotope effects - Abstract
The objective of this work is to propose a more effective way to prepare an in-house CO
2 with known triple oxygen isotope compositions. The major experimental steps include: (1) the O2 is combusted to CO2 on a graphite rod at 750 °C with Pt-catalyst for 3–4 min; and (2) converted CO2 is subsequently purified by two cryogenic traps. The results show high reproducibility of δ13 C and δ18 O values of the converted CO2 within 0.010–0.020 ‰ and 0.006–0.010 ‰ (1σ, SD), and the identical δ18 O value within error with that of the original O2 . Additionally, we have measured the triple oxygen isotope compositions of converted CO2 using an O2 –CO2 Pt-catalyzed oxygen-isotope equilibration method. The measured δ17 O values of CO2 show high reproducibility within 0.006 ‰ (1σ, SD), and are identical within error with the original O2 as well. Notably, our experiments also found that the O2 with heavier oxygen isotope ratios (δ18 O > 40 ‰, VSMOW) might have a lesser conversion efficiency, and this effect, combined with the lighter isotope preferential fractionations during the reaction processes of O2 to CO and CO to CO2 , may explain the observed lower17 O/16 O and18 O/16 O ratios of the converted CO2 relative to the original O2 . [ABSTRACT FROM AUTHOR]- Published
- 2021
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