Microplasma emission spectroscopy of carbon dioxide using the carbon monoxide Ångström system.

The present paper describes a system and method for indirect emission spectroscopy of CO₂ in the visible spectrum. This is achieved by using a microplasma spectrometer that first converts CO₂ into CO and then measures emissions from the CO Ångström system (B¹Σ ⁺ → A¹Π) at 560 nm. The experiments were performed on gaseous samples of CO₂, mixed in both N₂ and air, to concentrations between 0.01% and 100%. In addition to the microplasma spectrometer, the process was monitored by mass spectrometry with a residual gas analyzer. The CO₂ to CO conversion efficiency was found to be very high, reaching a maximum of 41% at close to 100% selectivity. Furthermore, the CO Ångström system was shown to facilitate excellent spectroscopic measurement of CO₂ concentrations below 10%, with a linearity of R² > 0.99 and an expected limit of detection in the parts-per-thousands range. The most promising aspect of the results was that the analysis was performed on extremely small total sample amounts where the gas flow through the systems was in the 0.1 µmole/s range. Hence, the present system has the prospect of filling a void in current sensor technology, where inexpensive and easy-to-use optical systems, such as nondispersive infrared sensors, cannot handle small sample amounts, while mass spectrometers, which can handle such samples, still are expensive, complex, and bulky. [ABSTRACT FROM AUTHOR]