Optimization and comparison of miniaturized extraction techniques for PAHs from crude oil exposed Atlantic cod and haddock eggs

Abstract

Two miniaturized extraction methods for a wide range of 2-6 ring polycyclic aromatic hydrocarbons (PAHs) and their alkylated homologues in small lipid-rich biota samples (≤100 mg) have been developed. Both methods utilize liquid extraction (LE) prior to a clean-up step using either normal phase solid phase extraction (SPE) or mixed-phase dispersive SPE (dSPE). Optimization of the methods was achieved by comparing the type and amount of sorbents, drying agents, and solvents used. In order to improve the limits of detection (LOD) of target PAHs under high sensitivity gas chromatography–tandem mass spectrometry analysis, specific emphasis was given to minimizing lipid co-extraction. The optimized LE–SPE method comprised extraction with dichloromethane/n-hexane (1:1, v/v) and clean-up by silica SPE, whereas the optimized LE–dSPE method comprised extraction with acetonitrile and clean-up with PSA and C18 sorbents. The methods were validated and directly compared through the analysis of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) eggs exposed to oil. The LE–SPE method resulted in lower levels of co-extracted lipids (14.1 ± 1.7 ng/μL) than the LE–dSPE method (60 ± 14 ng/μL). Achieved PAH LODs for the LE–SPE method were typically an order of magnitude lower (<5 ng/g) than for the LE–dSPE method (<125 ng/g). The LE–SPE method offers the possibility for PAH analysis of small samples of fish eggs (~100 mg) exposed to small quantities of crude oil (~1–10 μg/L total PAHs).

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