Simultaneous determination of 4-nonylphenol and bisphenol A in sewage sludge

Abstract

An analytical method has been developed for simultaneous extraction and determination of two estrogenic active agents, 4-nonylphenol (4-NP) and bisphenol A (BPA), in activated sewage sludge and anaerobically stabilized sewage sludge. Both compounds were determined by GC/MS in freeze-dried sewage sludge samples that had been spiked with these compounds in order to indicate different contamination levels. Extractive steam distillation, Soxhlet extraction, supercritical fluid extraction (SFE), and accelerated solvent extraction (ASE) were applied, and the results were compared. ASE under use of ethyl acetate/formic acid and an extraction temperature of 170 degrees C provided the most efficient extraction procedure for simultaneous extraction and the only reliable extraction results. Analyses of the phenolic compounds were performed by capillary column gas chromatography/mass spectrometry (GC/MS), operating in selected ion monitoring (SIM) mode after an aluminum oxide column-cleanup step prior to acetylation. The observed recovery rates under optimized conditions-ASE with ethyl acetate/formic acid-for 4-NP in spiked activated sewage sludge samples (spiking levels: 51, 88, or 554 microg/g on dry weight basis (dwb)) were 90, 107, or 101%. BPA (spiking levels: 50, 87, or 474 microg/g dwb) was found with recovery rates of 70, 105, or 101%, respectively. For anaerobically stabilized sewage sludge, recoveries for 4-NP (spiking levels: 40, 66, or 196 microg/g dwb) were 97, 95, or 101% and 90, 95, or 101% for BPA (spiking levels: 41, 67, or 474 microg/g dwb), respectively.