Determination of nonylphenol and octylphenol ethoxylates in effluent by liquid chromatography with fluorescence detection

A robust liquid chromatographic (LC) method with fluorescence detection is described for the simultaneous determination of the nonionic surfactants nonylphenol ethoxylates (NPEO) and octylphenol ethoxylates (OPEO) in effluent samples from sewerage treatment plants. The cleanup procedure uses graphitized carbon black solid-phase extraction cartridges. A subsequent derivatization step removes matrix interferences that are no longer fluorescent after acetylation. The efficiency of the method is monitored by inclusion of a surrogate compound designed and synthesized specifically for this purpose. The limit of reporting for the method is 5 μg/L for 100 mL effluent samples. Studies on confirmation of identity of NPEO and OPEO by electrospray LC/mass spectrometry are described.