Experimental design approach to the optimisation of hydrocarbons extraction from the sediment: Method development and application

Extraction and analysis of organic pollutants from matrices such as sediment constitute an essential step in environmental research. However, the extraction for quantitative analysis can turn out to be difficult because these compounds are present in trace levels and can be strongly bound to the sorbent matrix. Consequently, accuracy of environmental analyses mainly depends on the efficiency and the robustness of the extraction step. In this work, a sequential ASE extraction procedure was applied to the extraction of polycyclic aromatic and aliphatic hydrocarbons (PAHs, Me-PAHs and n-alkanes) in sediment samples. The extraction protocol was developed for 26 PAHs, including the 16 PAHs of the United-States Environmental Protection Agency (EPA) priority list, for 17 alkylated PAHs homologues and for 29 n-alkanes (from n-C12 to n-C40). A set of 30 experiments was carried out for the determination of the optimal extraction conditions. The four parameters studied were pressure, temperature, extraction time and nature of the solvent. Extracts were analyzed by gas chromatography (GC-MS and GC-FID) after clean-up and concentration. The optimal extraction conditions selected for pressure, temperature, extraction time and nature of solvent were respectively 14 MPa, 160 °C, 24 min and hexane/acetone (1/1 v/v). The analytical procedure was validated by comparing predicted and experimental values of sediment samples and by analyzing standard reference material. The validated method was then applied to establish a depth profile contamination in the sediment of the Deûle River in Northern France.