Ultrafast laser analysis of nitro-PAHs using laser desorption/femtosecond ionization mass spectrometry

Analytical interest in nitrated polycyclic aromatic hydrocarbons (nitro-PAH s) is related to their high mutagenicity and potential presence in a variet y of environmental media such as diesel exhaust and urban air particulate m atter. Furthermore, fundamental interest in these molecular systems stems f rom the photophysics,of the labile NO2 functional group, which has been inv estigated using mass spectrometry. The nitro-PAHs, 1-nitronaphthalene, 9-ni troanthracene, and 1-nitropyrene, have been studied using both femtosecond (lambda = 395 and 790 nm) and nanosecond (lambda = 266 nm) lasers coupled t o a reflectron time of flight mass spectrometer. Analysis of mass spectra t aken over a range of intensities (10(14)-10(15) W/cm(2)) has demonstrated t hat structurally specific ions can be observed. for each molecule, with lit tle or no fragmentation at lower intensities. It has also been found that a n intact parent ion can be detected using femtosecond ionization at 395 mn in each case. This work demonstrates the potential use of laser desorption/ femtosecond laser mass spectrometry (LD/FLMS) as an analytical technique fo r the detection of nitro-PAHs and other environmental pollutants and as a m eans of studying the photodynamics of labile molecular systems.