Fast filter-sampling and analysis of PAH aerosols by laser multiphoton ionization

Abstract

Most current methods for analysis of airborne polycyclic aromatic hydrocarbon (PAH) aerosols are based on filter sampling. We propose a new method for fast screening of the PAH contaminated filters, using laser induced multiphoton ionization (MPI), coupled to a fast-conductance (FC) detection scheme. We show that the porous morphology of glass fiber filters allows direct application of the MPI-FC technique. The results obtained by this method are compared to traditional solvent extraction followed by liquid chromatographic analysis. It has been found that the MPI-FC data represent a surface analysis, rather than a bulk integration. This has been confirmed by performing fluorescence imaging microscopy on the same filters. The calibration plots of the MPI-FC method are linear as long as the outer surface of the sampling filter is not saturated with PAH particulates. When stacking of particulates starts, quantification fails. Several other limitations, resulting from the very nature of this method, are discussed. The sensitivity for PAHs is adequate for environmental analysis and MPI readouts can be obtained after only a few seconds of sampling. Therefore, it is concluded that the method can probably be used for fast screening of PAH aerosols, and for providing the first indication of such a contamination.