High-precision 18O/16O, 13C/12C, 17O/16O analyses for µg-CaCO3

"High-precision simultaneous 18O/16O, 13C/12C and 17O/16O analyses for µg-quantities of CaCO3 by tunable infrared laser absorption spectroscopy" has been published in ACS Analytical CHemistry

 

Stable isotope ratios in carbonates have contributed greatly to understanding of Earth and planetary systems, climates, and history. Current methods for measuring isotopologues of CO2 derived from CaCO3 are primarily gas-source isotope ratio mass spectroscopy (IRMS). However, IRMS has drawbacks, such as mass overlap by multiple CO2 isotopologues and contaminants, the requirement of careful sample purification, and use of major instrumentation needing permanent installation and a high power electrical supply. Here we report simultaneous 18O/16O, 13C/12C and 17O/16O analyses for µg-quantities of CaCO3 using a tunable mid-infrared laser absorption spectroscopy (TILDAS) system, which preserves samples unchanged, has no mass overlap problem, and yields high sensitivity/precision measurements that completely comparable to conventional IRMS. We also show, for the first time, the relationship between 17O/16O ratios measured using the TILDAS system and published d17O values of international standard materials measured by IRMS. Our benchtop TILDAS system, with cryogen-free sample preparation vacuum-lines for µg-quantities of carbonates, is therefore a significant advance in carbonate stable isotope ratio geochemistry and is a new alternative to conventional IRMS.