Direct Observation of Polycyclic Aromatic Hydrocarbons on Geosorbents at the Subparticle Scale

We use the new analytical technique of microprobe two-step laser desorption/laser ionization mass spectrometry (μL 2 MS) to identify and characterize trace hydrophobic organic compounds found as contaminants on geosorbents. Specifically, we examine one laboratory-prepared sample and three aged field samples for the presence of polycyclic aromatic hydrocarbons (PAHs). The resolution of the present μL 2 MS instrument is a circular spot size 40 μm in diameter, with the potential to be much less. We report PAH distributions across individual particles as well as from particle to particle. Our data show lateral variations in the extent of sorption at the subparticle scale, which indicates that sorption phenomena are heterogeneous at subparticle dimensions.