Time-resolved laser-induced fluorimetry for screening polycylic aromatic hydrocarbons on solid-phase extraction membranes

The potential of solid-phase extraction (SPE) time-resolved laser-induced fluorimetry (TRLIF) is evaluated for screening polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. Octadecyl membranes are used with the dual purpose of extracting the pollutants from the water sample and serving as the solid substrate for fluorescence detection. Excitation of fluorescence is performed with a Nd:YAG pumped tunable dye laser pumped with a pulsed source for time-resolving spectral interference. Wavelength time matrices (WTMs) and real time-resolved fluorescence spectra are recorded with a pulsed delay generator, a spectrograph and an intensified charge-coupled device (ICCD). In comparison to SPE solid-matrix luminescence (SML) with conventional instrumentation, this approach provides better limits of detection (LOD) and selectivity. The improvement in LOD is of one order of magnitude, reaching the parts-per-trillion level with 10 ml of water sample. The improvement in selectivity allows the direct determination of target compounds in complex samples. The direct determination of benzoa]pyrene from a spiked river water sample of unknown composition is presented.