Determination of non-ionic polyethoxylated surfactants in sewage sludge by coacervative extraction and ion trap liquid chromatography–mass spectrometry

Alkylphenol polyethoxylates (APE, nonyl and octyl) and alcohol ethoxylates (AE, C12–C16) were analysed in sewage sludge by extraction with sodium dodecane sulphonate (SDoS), that undergoes coacervation under acid conditions, followed by quantitation with liquid chromatography/atmospheric pressure chemical ionisation ion/trap mass spectrometry, in positive ion mode. Coacervative extraction was optimised using an aged, fortified dehydrated sludge. Recoveries ranged from 78 to nearly 100% irrespective of the sludge matrix analysed. The method provided good agreement between the ethoxamer distribution of surfactants after extraction from sludge and that in the original surfactant. Detection limits for polyethoxylated surfactants in the sludge were 0.09–0.38 mg/kg. The procedure was used to assess the concentrations of APE and AE in activated and dehydrated sludge from two sewage treatment plants. Polyethoxylates were found in all samples in the concentration ranges 11–151, 100–138 and 23–141 mg/kg for octylphenol, nonylphenol and individual AE homologues, respectively. The method did not require clean-up or preconcentration steps.