Use of microextraction by packed sorbents following selective pressurised liquid extraction for the determination of brominated diphenyl ethers in sewage sludge by gas chromatography–mass spectrometry

• A PLE-MEPS-GC–MS/MS method was developed to determine BDEs in sewage sludge.
• MEPS provides sensitivity enhancement, resulting in a decrease of detection limits.
• Automated on-line extract clean-up improves detection and protects GC–MS from dirt.
• Sewage sludge from La Rioja showed BDE levels between 53.9 and 76.8 ng g−1.

In this work, a method based on selective pressurised liquid extraction followed by microextraction by packed sorbents (MEPS) for the determination of brominated diphenyl ethers (BDEs) in sewage sludge is presented. The factors affecting the MEPS procedure were optimised. Acetone:water (25:75) sPLE extracts were drawn-ejected 10 times through C18 cartridges at 5 μL s−1. The cartridge was dried five times with 250 μL of air and the BDEs were eluted at 25 μL s−1 with 100 μL of n-hexane that were directly injected at 13 μL s−1 in the GC–MSMS system. Under these conditions, there were no carry-over effects. The method was characterised in terms of limits of detection, repeatability, intermediate precision and accuracy. The use of MEPS for the determination of BDEs in sewage sludge means an improvement of the limits of detection due to the preconcentration and clean-up performed before the injection of the whole elute in the PTV injector. The GC–MSMS LODs (25 pg mL−1) were improved with MEPS to less than 3 pg mL−1. RSD less than 7% and recovery values from 92% to 102% were shown. Finally, the method was applied to the sPLE extract analyses of sewage sludge from several wastewater treatment plants in La Rioja. To our knowledge, this is the first time that the MEPS technique has been applied to the analysis of BDEs, and the first time that it has been used for the analysis of extracts from a solid sample.