Parametric study of polycyclic aromatic hydrocarbon laser desorption

We present the use of a combined laser desorption/multi-photon ionization/time-of-flight mass spectrometry technique for the analysis of polycyclic aromatic hydrocarbon (PAH) solid samples. A thorough characterization of the first step ( laser desorption) of this experimental technique has been performed. By varying the energy of the laser pulse, a specific response of each PAH has been evidenced for pure and mixed PAH sample desorption. This behaviour has also been studied with respect to the fragmentation processes. Similar studies on PAHs adsorbed on graphite evidenced the possibility of desorbing molecules from the adsorbed phase only, i.e. without a contribution from the graphite substrate. These findings represent important preliminary steps towards the final goal of setting up a completely characterized analytical method for the investigation of the adsorbed phase of soot particles generated in combustion processes.