Investigations into a novel method for atmospheric polycyclic aromatic hydrocarbon monitoring

摘要

A novel analytical method for atmospheric polycyclic aromatic hydrocarbons (PAHs) was developed based on laser induced fluorescence (LIF) of samples on quartz multi-channel polydimethylsiloxane traps. A tunable dye laser with a frequency doubling crystal provided the excitation radiation, and a double monochromator with a photomultiplier tube detected emitted fluorescence. The method allowed for the rapid (< 5 min), cost effective analysis of samples. Those yielding interesting results could be further analysed by direct thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS, with limits of detection of ～0.3 ng m~(-3)), as photodegradation was minimal (< 10% over 5 min irradiation). Small amounts of naphthalene photodegradation products identified by TD-GC-MS after > 15 min irradiation, included phenol, benzyl alcohol and phthalic anhydride. Without any signal optimization, a LIF detection limit of ～1 μg m~(-3) was established for naphthalene using a diffusion tube (diffusion rate of 2 ng s~(-1)) and 292 nm excitation.