Advances in optical methods for trace gas analysis

Sensing of Halocarbons Using Femtosecond Laser-Induced Fluorescence

“…5 On-line, in situ approaches have also been proposed, using, for example, open-path spectroscopic techniques such as Fourier transform infrared spectroscopy (FT-IR) and tunable diode laser infrared spectroscopy (TDLAS) to provide the advantage of in situ measurements by propagating a light beam through the system to be monitored and using the absorption "fingerprint" of halogenated alkanes in the infrared region from 7 to 12.5 µm. [9][10][11] The possibility to perform real-time, on-line monitoring of halocarbons has also been demonstrated using at least two laserbased techniques that do not rely on molecular absorption of IR light: laser-induced breakdown spectroscopy (LIBS) and laser photofragmentation/fragment detection (PF/FD). Typical limits of detection (LOD) for the analysis of halogenated alkanes by LIBS are in the low ppmw range with selectivity usually limited to classes of compounds.…”

“…Pollutants of particular interest are halogenated alkanes (CFCs, halons, HCFCs, HFCs, PFCs), mainly because of their central role in ozone layer depletion and global warming. − The monitoring of halogenated alkanes at or near ground level can be done routinely using a variety of sensitive and selective analysis techniques, often using on-site air sampling and off-line gas chromatography combined with mass spectrometry (GC/MS), microwave-induced plasma atomic emission spectroscopy (GC/MIP-AES), , or flame ionization detection (GC/FID) . On-line, in situ approaches have also been proposed, using, for example, open-path spectroscopic techniques such as Fourier transform infrared spectroscopy (FT-IR) and tunable diode laser infrared spectroscopy (TDLAS) to provide the advantage of in situ measurements by propagating a light beam through the system to be monitored and using the absorption “fingerprint” of halogenated alkanes in the infrared region from 7 to 12.5 μm. − …”