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Determination of nonylphenol polyethoxylates and their lipophilic metabolites in sewage effluents by normal-phase high-performance liquid chromatography and fluorescence detection

Analytical procedures using normal-phase high-performance liquid chromatography (HPLC) with fluorescence detection suitable for the routine determination of alkylphenol polyethoxylate (APnEO) surfactants and their lipophilic metabolites in sewage effluents at sub-microgram per litre level have been developed. The parent nonylphenol polyethoxylates (NPnEO), covering oligomer range of 1-18 ethoxy units per molecule, were extracted from water samples using solid-phase extraction on graphitised carbon black (GCB), while their lipophilic metabolites, including nonylphenol monoethoxylate (NP1EO), nonylphenol diethoxylate (NP2EO) and nonylphenol (NP), were extracted by liquid-liquid extraction into n-hexane. The extracts were analysed by normal-phase HPLC by using amino-silica columns and fluorescence detection at 228/305 nm. This allowed reliable quantitative determination of individual oligomers down to 0.1 mg/l. Analyses of sewage effluents collected in several sewage treatment plants of the Canton of Zürich, Switzerland, indicated that NPnEO occur at significant concentrations (96-430 mg/l) despite the partial ban introduced in 1986. Oligomer distributions found in analysed sewage samples revealed that the major part of toxic lipophilic metabolites, including NP, still originate from detergent-derived NPnEO.

nonylphenol polyethoxylates; nonionic surfactants; nonylphenol; normal-phase HPLC; sewage effluents

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