Quantification of minor trace-gas pollutants in air by variable pressure infrared diode laser spectroscopy
Résumé
We recently developed a new protocol for the measurement of minor trace-gas pollutants in air : variable pressure infrared diode laser spectroscopy (Dusanter et al., Applied Optics, vol.41(24), pp. 5142-5147, 2002). Instead of scanning the laser emission around the feature of interest at a fixed pressure and adjusting the 2f absorption line to a calibrated spectrum, we stabilize the laser emission at the center of the line and measure the change in 2f intensity while the pressure increases inside the cell from 0 to about 20 Torr. The resulting curve of intensity versus pressure is in the low pressure range a straight line, with a slope proportional to the volume fraction of the absorbant. This procedure has been compared to the standard one, on the same instrument, and has been shown to lead to the same detection limit. However, it benefits from its ability to quantify heavier species with no isolated line, such as 1,3butadiene, from its simplicity in the data analysis phase, and from its lower sensitivity to variations of the baseline. We will present in this poster our results on 1,3-butadiene, formaldehyde and acetaldehyde, as well as our ongoing work toward an automated field instrument.
Domaines
Chimie théorique et/ou physique
Origine : Fichiers produits par l'(les) auteur(s)