OPTIMIZATION AND VALIDATION OF SOLVENT AND SUPERCRITICAL-FLUID EXTRACTIONS FOR THE TRACE-DETERMINATION OF POLYCYCLIC AROMATIC-HYDROCARBONS IN SEWAGE SLUDGES BY LIQUID-CHROMATOGRAPHY COUPLED TO DIODE-ARRAY AND FLUORESCENCE DETECTION

There is a need for a better characterization of sludges from wastewat er treatment plants which are destined to be spread on agricultural la nd. Inorganic pollutants are regularly controlled, but organic polluta nts have received little attention up to now. The main problem for tra ce analysis of organic pollutants comes from the complexity of the var ious matrices of sludges, which depends on their origins. Therefore, m ethods described for soils and sediments cannot be directly applied to sludges which contain high amount of Lipids. This paper provides a me thod for trace-determination of polycyclic aromatic hydrocarbons in th e range of mg/kg of dried sludge including an extraction step, and an analysis step by liquid chromatography with fluorescence detection for sensitive quantification and W-diode-array detection for confirmation . The extraction step was optimized by a selection of the solvent used for both Soxhlet and supercritical-fluid extraction and by setting th e experimental conditions(temperature, pressure, modifier, etc.) used for SFE. Extraction recoveries were found similar and quantitative for the two procedures. However supercritical-fluid extraction appears to be a good alternative to Soxhlet extraction because of the consumptio n of less time and solvent. Detection limits were obtained in the rang e of 0.1-1 mg/kg of dried sludges, with possible confirmation by UV sp ectra. The whole method (extraction/quantification/ confirmation) was validated using sludges which have been certified by the Community Bur eau of Reference from Brussels (CRM No. 088). Application to thr deter mination of PAHs in urban sludges is presented. (C) 1998 Elsevier Scie nce B.V. All rights reserved.