[B-PT02] Biomineralization and Geochemistry of Proxies

[BPT02-11] Sensitive stable isotopic analyses of carbonates using Mid-infrared laser spectroscopic techniques

★Invited Papers

*Saburo Sakai¹ (1.Japan Agency for Marine-Earth Science and Technology)

Keywords:CO2, Isotopologues, laser spectroscopy

Stable isotope ratios of carbonates have contributed to understanding of Earth and planetary systems, especially in field of paleoclimate and paleoceanography. Current method for measuring the stable isotope ratios of CO₂ is primarily gas-source isotope ratio mass spectroscopy (IRMS). However, even high-precision IRMS does not fully satisfy the recent demands for isotopic microanalysis of carbonates and organic compounds and also for detection of rare isotopologues. Here I show a cutting edge method using a tunable mid-infrared laser direct absorption spectroscopy (TILDAS) with cryogen-free sample preparation system for measuring stable isotopes from subnanomolar CO₂. This TILDAS system can analyze 18O/16O and 13C/12C in a minimum volume of 0.3 nanomolar (0.03 µg CaCO3 and 3.8 ng carbon with equivalent precision to IRMS), which is one order of smaller sample size than current available sensitive analytical techniques. Therefore, this method opens a new realm for both practical and sensitive CO₂ isotopic analyses, and also for high-resolutional application of rare isotopologues such as 17O/16O and carbonate clumped isotopes. I will represent recent advances of this laser spectroscopic technique and its perspectives for applying paleoclimatology.