Development of an analytical method for the determination of polybrominated diphenyl ethers in sewage sludge by the use of gas chromatography coupled to inductively coupled plasma mass spectrometry

• A new analytical procedure for the determination of six PBDEs in sewage sludge was developed.
• PBDEs were extracted with HCl/MeOH, and addition of Tris-citrate buffer and iso-octane.
• Concentrations of PBDEs in the organic phase (iso-octane) were determined by GC-ICP-MS.
• The procedure developed is simple, accurate, repeatable, reproducible and sensitive.
• BDE 47 and BDE 99 were the most abundant BDE congeners in sludge samples analysed.

Polybrominated diphenyl ethers (PBDEs) are flame retardants. As a consequence of their widespread use, they have been released into the environment. PBDEs are lipophilic organic contaminants that enter wastewater treatment plants (WWTPs) from urban, agricultural and industrial discharges. Because of their low aqueous solubility and resistance to biodegradation, up to 90% of the PBDEs are accumulated in the sewage sludge during the wastewater treatment. To assess the possibilities for sludge re-use, a reliable determination of the concentrations of these PBDEs is of crucial importance. Six PBDE congeners (BDE 28, BDE 47, BDE 99, BDE 100, BDE 153 and BDE 154) are listed as priority substances under the EU Water Framework Directive. In the present work a simple analytical method with minimal sample-preparation steps was developed for a sensitive and reliable determination of the six PBDEs in sewage sludge by the use of gas chromatography coupled to inductively coupled plasma mass spectrometry (GC-ICP-MS). For this purpose an extraction procedure was optimised. Different extracting agents (methanol (MeOH), acetic acid (AcOH)/MeOH mixture (3:1) and 0.1 mol L−1 hydrochloric acid (HCl) in MeOH) followed by the addition of a Tris-citrate buffer (co-extracting agent) and iso-octane were applied under different modes of extraction (mechanical shaking, microwave- and ultrasound-assisted extraction). Mechanical shaking or the microwave-assisted extraction of sewage sludge with 0.1 mol L−1 HCl in MeOH and the subsequent addition of the Tris-citrate buffer and the iso-octane extracted the PBDEs from the complex sludge matrix most effectively. However, due to easier sample manipulation during the extraction step, mechanical shaking was used. The PBDEs in the organic phase were quantified with GC-ICP-MS by applying a standard addition calibration method. The spike recovery test (recoveries between 95 and 104%) and comparative analyses with the species-specific isotope-dilution (ID) GC-ICP-MS confirmed the accuracy of the developed analytical procedure. The procedure is sensitive (limits of detection (LODs) for PBDEs congeners between 0.2 and 0.3 ng g−1), repeatable and reproducible (RSDs 2.2–5.7%) and was applied for the determination of PBDEs in sewage sludge samples collected three times at the municipal WWTP over a period of 16 years.

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