In-cell clean-up pressurized liquid extraction for the analysis of brominated diphenyl ethers in sewage sludge by GC-NCI-MS

Abstract

An automated and sensitive method based on in-cell clean-up pressurized liquid extraction (PLE) was developed and validated for the simultaneous determination of 14 brominated diphenyl ethers in sewage sludge samples. Extraction and online clean-up were integrated into one step using PLE with in-cell clean-up (3 g acidic silica and 4 g florisil). The effects of various operational parameters on the performance of extraction and online clean-up procedures were carefully investigated, and optimum results were obtained when the conditions were fixed at 100 °C, 1500 psi, and two extraction cycles with a heating time of 5 min using hexane/dichloromethane (50 : 50, v/v) as extraction solvents. Separation and quantification of target compounds were carried out by gas chromatography-mass spectrometry with negative chemical ionization (GC-NCI-MS). The in-cell PLE method was evaluated by repeated analysis of target compounds from spiked sewage sludge and excellent recoveries (85–105%) were observed for most analytes at each spiking level, with the RSD values being generally below 15%. Finally, the method was applied to the analysis of real sewage sludge samples from wastewater treatment plants located in Shanghai (China), where the dominant brominated diphenyl ether was BDE-209, with concentration levels between 54.86 and 215.10 ng g⁻¹ dry weight.