Focused ultrasound solid–liquid extraction and selective pressurised liquid extraction to determine bisphenol A and alkylphenols in sewage sludge by gas chromatography–mass spectrometry

A new method for determining endocrine disrupter compounds (EDCs) in sewage sludge is described in this paper. EDCs studied were bisphenol A (BPA) and alkylphenols (APs). In order to obtain a fast and simple method, selective pressurised liquid extraction (SPLE) and focused ultrasound solid–liquid extraction (FUSLE) were tested. Best results for SPLE were obtained using Florisil as clean‐up sorbent and dichloromethane as extraction solvent, while temperature was the only significant variable. Analyte extraction by SPLE was completed in only one extraction cycle of 1 min at 130°C. FUSLE was carried out in one step of 20 s at 75% power (0.5 cycles) and with 8 mL of ethyl acetate. Although the optimised FUSLE process was faster, simpler and cheaper, SPLE provided higher recovery values (ranging from 81 to 105%) and therefore SPLE‐based method was selected and validated. The SPLE and GC‐MS method showed an LOD of 10.7 ng/g for BPA and LODs between 1.2 and 41.6 ng/g for APs. Relative standard deviation values lower than 6% were obtained for all analytes. As a result, an efficient, fast and simple method based on SPLE and GC‐MS for the determination of BPA and APs in sewage sludge is proposed.