Screening of Polycyclic Aromatic Hydrocarbons in Soil by On-Line Fiber-Optic-Interfaced Supercritical Fluid Extraction Spectrofluorometry

Abstract

An interface for spectrofluorometric measurements in the supercritical (SC) CO2 emerging from the extraction cell of a supercritical fluid extractor prior to depressurization was developed. The windowless flow cell designed for this purpose is furnished with an inlet and outlet for the SC-CO2 stream; it can withstand pressures up to at least 350 bar and is connected to the light source and detector by means of two fiber-optic cables. The combined system allows the real-time on-line fluorometric monitoring of the supercritical fluid extraction (SFE) process and provides qualitative and semiquantitative information from supercritical extracts of real and spiked samples. The determination of five polycyclic aromatic hydrocarbons (PAHs) in spiked soil by SFE with on-line fluorescence detection provided relative standard deviations less than 5%, as well as benzo[k]fluoranthene recoveries from several spiked soils between 93 and 107%, with an RSD less than 10%. Also, crysene−benzo[a]anthracene binary mixtures in spiked soil were resolved with recoveries of 89−103% and an RSD of about 10%. The use of the proposed equipment for screening real soil samples for PAHs using on-line SFE spectrofluorometry is demonstrated.