Extraction and cleanup of PAHs

Before analysis, the samples were fortified with an internal standard solution of perdeuterated homologues of analytes, used as reference compounds for quantification. The standard solution contained fluoranthene, phenanthrene, chrysene, benzo(a)anthracene, benzo(a)pyrene, perylene, benzo(ghi)perylene, and dibenz(a,h)anthracene. Filters were extracted three times for 20 min in an ultrasonic bath using a mixture of dichloromethane, acetone, and methanol (45:45:10 % v/v).

The extract was first evaporated under a gentle stream of nitrogen and purified by liquid chromatography on a neutral alumina column (6 g, deactivated with 2.5% water), then PAHs were recovered through elution with dichloromethane:isooctane (40:60 in volume, 15 mL); the eluate was reduced close to dryness under nitrogen, dissolved with toluene and analyzed by GC-MS.