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

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.