PLE and GC–MS Determination of Polybrominated Diphenyl Ethers in Soils

We describe a pressurized liquid extraction (PLE) method, followed by gas chromatography-mass spectrometry, for the determination of polybrominated diphenyl ethers (PBDEs) in soil samples. Different extraction solvents (isohexane, dichloromethane, acetone and methanol), either alone or in combination, were used to extract these target compounds from spiked soil samples. Variables affecting the PLE extraction efficiency, such as pressure, temperature, number of extraction cycles and static extraction time were studied; the optimum parameters were 1,500 psi, 100 °C, 1 cycle and 5 min, respectively. Purification of crude extracts from the PLE system was achieved by adsorption chromatography using different proportions of acid silica and activated silica; the most effective mixture being either 10 g acid modified silica : 5 g silica or 15 g acid modified silica : 0 g silica. The PLE based method was compared with more traditional Soxhlet and ultrasonic extraction methods; overall the mean percentage recoveries using PLE were 95 ± 9%, and compared favourably with the Soxhlet 94 ± 4% and were better than the ultrasonic method 108 ± 36%. The limits of detection and quantification of the proposed method were 11–54 and 38–180 pg g−1, respectively, for the different PBDE studied. The developed method was linear over the range from 0.05 to 30 ng g−1 except for PBDE 183 of 0.10–30 ng g−1. The established method was successfully applied to soil samples from Scotland, UK, for the determination of the target PBDEs.