Contaminated aerosols, produced by internal combustion processes, are of considerable environmental concern. Laser Induced Fluorescence (LIF) was applied for fast analysis of such aerosols. A "cold-plate type" sampler, held at several fixed temperatures, was used for the in-situ, rapid pre-concentration of them. This way, the ambient air moisture vapors quickly condense into microscopic size water droplets. These, in turn, become polluted by the incoming flux of aerosols that, while being captured within, undergo accumulation (dissolve or suspend). Comparative sensitivity of LIF spectra to application of a non-polar solvent (hexane) to these contaminated aqueous samples is addressed. Insitu obtained LIF spectra allow non-destructive characterization of vehicle engine performance.