Analysis of sulfuric acid aerosols by laser-induced breakdown spectroscopy and laser-induced photofragmentation

Laser-induced breakdown spectroscopy and laser photofragmentation spectroscopy are investigated as potential approaches to the detection and quantification of the sulfuric acid aerosols resulting from the oxidation of dimethylsulfide in air. The former, direct technique, where aerosols are introduced in the plasma formed by focusing the fundamental frequency of a Nd:YAG laser in air, and atomic sulfur emission is measured in the region 180 nm, gives a limit of detection of 165 ppbv for a 15 min integration time, which is inadequate for our purposes. The second, indirect approach, based on the photofragmentation, with 193 nm photons, of the compound resulting from interaction between sodium chloride and sulfuric acid aerosols, gives a detection limit of 46.5 ppbv in 10 s measuring time. With this method, a complete "titration curve" for sulfuric acid aerosols can be obtained in "quasi" real-time.