[M-IS15] Paleoclimatology and Paleoceanography

[MIS15-23] Supersensitive analyses of carbon dioxide isotopologues using Mid-infrared laser spectroscopic techniques and its perspectives for paleoclimatology

★Invited Papers

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

Keywords:Mid-infrared laser spectroscopy, CO2 isotopologues, supersensitive analyses

Stable isotope ratios of CO₂ 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 “portable” 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 with standard errors of less than 0.1 ‰ in a minimum volume of 0.3 nanomolar (equivalent to 0.03 µg CaCO3 and 3.8 ng carbon), which is one order of smaller sample size than current available sensitive analytical techniques. Therefore, this method opened a new realm for both practical and supersensitivity CO₂ isotopic analyses, and also for 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.