Direct automatic screening and individual determination of polycyclic aromatic hydrocarbons using supercritical fluid extraction coupled on-line with liquid chromatography and fluorimetric detection

A fast, simple method that allows the direct screening of sediment samples for polycyclic aromatic hydrocarbons (PAHs) by the use of a flow manifold coupled online to a fluorimetric detector is reported. The method avoids the need to use expensive instruments such as a liquid chromatograph equipped with a scanning fluorescence detector. The proposed experimental set-up allows PAHs in supercritical fluid extracts to be selectively retained on a column packed with polytetrafluoroethylene (PTFE) accommodated in the loop of a high-pressure injection valve. Retained PAHs are subsequently eluted with acetonitrile and directly driven to the fluorimetric detector. Samples testing positive for PAHs are subjected to liquid chromatography in order to separate, identify, and quantify the analytes. This allows anthracene, pyrene, benzo(a)anthracene, 1,2-benzodiphenylene sulfide and benzo(k)fluoranthene to be quantified. The proposed method provides analytical information of two types, namely: (a) a yes/no overall response and (b) confirmation of species in the samples testing positive for PAHs. The precision of the screening method for a 0.100 (mu)g ml^-1 mixture of PAHs, expressed as relative standard deviation (R.S.D.), was 3.9% (n=11). The determination of five PAHs in spiked sediment provided R.S.D. values less than 5.5% in all instances. PAH recoveries ranged from 89 to 110%. The method was validated by application to spiked sediment samples.