Optimised accelerated solvent extraction of PCBs and PAHs from compost

Abstract

This study is the first thorough method optimisation for accelerated solvent extraction (ASE) of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) from chemically dried compost. For PCBs, optimised solvent composition, temperature, pressure, number of static cycles, duration, and flush volume were as follows: toluene/acetone 1 : 3 (v/v), 120°C, 2000 psi, 3 × 5 min, and 50%, respectively. Limits of quantification and method precision were between 0.16 and 2.46 µg kg⁻¹ dw and 6–17% respectively for individual PCBs. Absolute recoveries of isotope-labelled extraction standards used for each of the analytes ranged from 65 to 105% and relative recoveries were between 85 and 99%. The method proofed to be robust and was successfully applied to different compost samples.

The optimisation of PAHs extraction was performed and resulted in the following conditions: solvent: hexane/acetone 1/3 (v:v), temperature: 140°C, pressure: 1500 psi, extraction time: 3 × 5 min, and 50% flush volume. Limits of detection and method precision for individual PAHs were between 1.1 and 37.2 µg kg⁻¹ dw and 12–34% respectively. Absolute and relative recoveries ranged from 24 to 68% and from 85 to 99%, respectively. Optimal extraction conditions for PAHs were more difficult to determine due to the inhomogeneous distribution of PAHs in samples. However, the method appeared to be feasible and suggestions for further improvements are presented.

Keywords:

• ASE
• Polychlorinated biphenyls
• Polycyclic aromatic hydrocarbons
• Sample preparation

Acknowledgements

We would like to acknowledge Hans Jörg Bachmann, Franziska Blum, Marianne Erbs and Niccolo Hartmann for helpful comments on the manuscript and analytical support, Markus Zennegg, Erika Gujer and Peter Schmid (Laboratory of Organic Chemistry at the Swiss Federal Laboratories for Material Testing and Research, EMPA) for the inter-laboratory comparison, and the Swiss Agency for the Environment, Forest and Landscape (SAEFL) and the Swiss Federal Office of Energy (SFOE) for their financial support.