Identification of 4-n-nonylphenol metabolic pathways and residues in aquatic organisms by HPLC and LC-MS analyses

In order to better assess the risk associated with nonylphenol, a lipophili c contaminant of the aquatic environment having a strong tendency to bioacc umulate in organisms and exerting estrogenic effects in fish and invertebra tes, we have investigated the capability of three types of freshwater speci es to metabolize labelled 4-n-nonylphenol. Reverse-phase radio-HPLC was use d to isolate and quantify the metabolites. The identification of residues w as based on co-chromatography with available standards or authentified meta bolites and when possible by electrospray ionization LC-MS analyses. The re sidues found in rainbow trout (Oncorhynchus mykiss), pond snails (Lymnea st agnalis) and duckweeds (Lemna minor) were identified. These freshwater orga nisms are able to extensively biotransform 4-n-nonylphenol. Our attempts to draw the metabolic pathways of nonylphenol evidenced oxidative attack on t he alkyl chain with the production of several hydroxylated compounds and re lated carboxylic acids. In addition, trout and duckweeds were able to conju gate the phenol moiety to glucuronic acid and carbohydrates respectively. T races of sulphate conjugates were also detected in trout tissues whereas no conjugate was detected in pond snails.