High-Precision Simultaneous 18O/16O, 13C/12C, and 17O/16O Analyses for Microgram Quantities

This paper describes the use of mid-infrared spectroscopy with a quantum cascade laser to measure stable isotopes of CO2. What is noteworthy is that the sensitivity and accuracy is equal to or better than conventional mass spectrometers, and the 17O measurement can be performed on CO2.
http://pubs.acs.org/doi/abs/10.1021/acs.analchem.7b00544