Carbon ratio convenience

Appl. Phys. Bhttp://dx.doi.org/10.1007/s00340-011-4666-1 (2011)

The ability to make precise measurements of the ratio between ¹³CO₂ and ¹²CO₂ in a gas sample is important for studying phenomena ranging from climate change and the release of volcanic gases to plant biochemistry and breath analysis. Although such measurements can be performed using isotope ratio mass spectroscopy, the necessary equipment is relatively large and complex, thus restricting it to laboratory use. Scientists from the University of Tokyo in Japan have now shown that wavelength modulation spectroscopy using a multipass gas cell and a 2 μm semiconductor laser could help to enable the realization of mobile isotope ratio mass spectrometers. Their wavelength modulation spectroscopy set-up had a detection limit of 16 parts per billion, a response time of three minutes and good stabilization (standard deviation of 1σ) of 0.24% over 10 hours, which is sufficient for accurate and real-time measurements of atmospheric CO₂. The researchers are considering the use of a double-cell system to further increase the precision of their measurements.