On the Determination of Benzo(a)pyrene in Atmospheric Aerosols Fractionated by a low Pressure Impactor, by TLC Separation andin situSpectrophotofluorometry at the Picogram Level

Urban aerosols were fractionated according to size by an eight-stage low pressure impactor with size resolution down to 0.05 μm diameter. Each stage of the impactor, containing picogram amounts of benzo(a)pyrene (BaP) and other polycyclic aromatic hydrocarbons (PAH) was ultrasonically extracted with benzene. After reduction to appropriate volumes, the extracts were spotted on a TLC plate and developed. The BaP spots were quantitated in situ by finely focusing the TLC plate on the fluorescence excitation beam and measuring the resulting emission while scanning the plate. The regression lines passing thru the origins exhibited linear regression coefficients (R 2) between 0.9985 and 0.9996 for three-point BaP calibration data in the 100-1000 picogram range. The relative standard deviations varied between 3.4 and 12.9%, depending on the amount of BaP present. The detection limit for BaP is 5 picogram. The method allows the determination of typical atmospheric Bap size distributions with as little as 1.5 m3 of sampled air.