Direct analysis of polycyclic aromatic hydrocarbons in cloud-water aerosol filtrates using laser desorption mass spectrometry

A novel technique for the rapid screening of polyaromatic hydrocarbons (PAHs) in atmospheric particulates is presented. Two-step laser desorption laser photoionisation time-of-flight mass spectrometry was used to assay for PAHs in cloud-water particulates collected near Peebles in southern Scotland. The particulates were examined in situ on their host filters removing the requirement for time-consuming sample extraction and separation. The mass spectra obtained from a single filter are shown. The principal components of these are assigned to PAH contaminants and phthalate contaminants. A distribution of PAHs was observed using 193 nm laser photoionisation. The mass spectrum obtained on using 248 nm laser photoionisation exhibits a different intensity distribution demonstrating an ionisation wavelength dependence. The utility of the technique for rapid screening of PAHs and other polyaromatic species is discussed.