Experimental Designs for Optimizing Multi-residual Microwave-assisted Extraction and Chromatographic Analysis of Oxygenated (Hydroxylated, Quinones) Metabolites of PAHs in Sediments

Abstract : Polycyclic aromatic hydrocarbons (PAHs) are persistent pollutants that accumulate in sediments, where they may be turned into more toxic oxygenated metabolites (oxy-PAHs). Two methodologies were screened for a multi-residue analysis of two different families of oxy-PAHs from sediments: hydroxylated PAHs (OH-PAHs) and carbonyl-PAHs (quinones). Microwave-assisted extraction (MAE), which has never been used for their simultaneous extraction, was optimized based on (1) a fractional factorial design to screen the influential factors and (2) a central composite design to obtain the best compromise for optimal extraction conditions, which were 128 °C, 26 mL of acetonitrile/methylene chloride (90/10) and 10 min duration. Individual recoveries were in the range 73.9–118%. Then GC-MS and HPLC coupled to UV and fluorescence (FLD) detectors were investigated for quantification of traces. OH-PAHs and quinones had to be derivatized before GC-MS. Acetylation of quinones was improved and limits of detection (LODs) were decreased 2.7–53 fold, with the highest benefit for ortho-quinones. There was no real advantage in using HPLC-UV instead of GC-MS in terms of carbonyl-PAH detection sensitivity, but OH-PAH LODs were decreased 30- to 140-fold using HPLC-FLD. Despite this advantage, MAE-GC-MS appeared the best way to analyze oxy-PAHs at trace levels from naturally contaminated sediment matrices, because confirmation of their presence in extracts was more reliable.