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 submicr on polycyclic aromatic hydrocarbon (PAH) aerosols by a combination of laser -induced-fluorescence (LIF) and laser multiphoton ionization (LMPI) techniq ues was investigated. For this purpose, an aerosol contaminated nitrogen ga s was slowly bubbled through a quartz measurement chamber filled with hexan e. Continuous PAH monitoring was maintained over two hours of the resultant concentration process. Simultaneous LIF and LMPI excitation was achieved b y a pulsed dye laser, operated at 283 nm. For this wavelength, pyrene and n aphthalene aerosols were used as target PAH materials. The resultant fluore scence 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.