An Improved Pressurized Liquid Extraction Method for the Determination of Polycyclic Aromatic Hydrocarbons in Freshwater Sediments by Gas Chromatography‐Mass Spectrometry

Abstract

An improved pressurized liquid extraction (PLE) method for polycyclic aromatic hydrocarbons (PAHs) in freshwater sediment is described. The optimized method is simple, fast, efficient, and requires small amounts of sample and generates small amounts of secondary waste. Five optimization factors were chosen for study: extraction temperature, extraction time, sample mass, solvent volume, and post‐extraction cooling time. Method development was performed using authentic PAH‐contaminated (“aged”) sediment samples; optimal conditions were identified based upon a response function (recovery/precision) for three representative PAHs (naphthalene, pyrene, and benzo[g,h,i]perylene). In the optimized method, 3.00 mL of n‐hexane and 0.500 g of sediment were heated in a closed stainless steel extraction cell for 60.0 min at 200°C. The cell was then placed in an ice bath for 5.0 min, and the PAH content of the collected extract was determined by gas chromatography‐mass spectrometry (GC‐MS). Detection limits for this method range from 0.0511 ± 0.0110 to 0.963 ± 0.0792 µg per gram of dried sediment sample for the sixteen PAHs classified by the U.S. Environmental Protection Agency (U.S. EPA) as “priority pollutants.” The method was validated by applying it to National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1944. The concentrations determined were, on average, within ±11% of the certified values (at the 95% confidence level). The PLE method described herein requires ∼90% less extraction solvent and yields a ∼45% improvement in precision compared to existing methods.

Keywords:

• Polycyclic aromatic hydrocarbons
• Pressurized liquid extraction
• Freshwater sediment
• Gas chromatography‐mass spectrometry
• Validation

Acknowledgments

This work was supported by the Great Lakes National Program Office of the United States Environmental Protection Agency (Project GL‐97514901‐0). Presented at the 55th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Chicago, Illinois.