On-line screening of airborne PAH contamination by simultaneous multiphoton ionization and laser induced fluorescence

In this preliminary study, the feasibility of on-line monitoring of submicron polycyclic aromatic hydrocarbon (PAH) aerosols by a combination of laser-induced-fluorescence (LIF) and laser multiphoton ionization (LMPI) techniques was investigated. For this purpose, an aerosol contaminated nitrogen gas was slowly bubbled through a quartz measurement chamber filled with hexane. Continuous PAH monitoring was maintained over two hours of the resultant concentration process. Simultaneous LIF and LMPI excitation was achieved by a pulsed dye laser, operated at 283 nm. For this wavelength, pyrene and naphthalene aerosols were used as target PAH materials. The resultant fluorescence light was collected by an optical fiber, while the LMPI signals were acquired by a pair of stainless steel electrodes immersed in the solution, allowing an automated readout of the photoionization current. The results indicate that PAH sub-micron aerosols, at an air concentration of 1 mg m(-3), can be monitored in this way.