Identification and enantioselective gas chromatographic mass-spectrometric separation of O-desmethylnaproxen, the main metabolite of the drug naproxen, as a new environmental contaminant.

O-desmethylnaproxen (2-(6-hydroxynaphthalen-2-yl)propanoic acid) was identified in 10 different water samples from Germany and Pakistan. In the Pakistan samples it was found in all samples, surface water and effluents, exhibiting estimated concentrations between 0.04 and 1.36 microg/L. In Germany it was only encountered in the STP-effluent with an average concentration of 0.23 microg/L. Furthermore, enantioselective GC analyses revealed differences in the enantiomeric ratios found in Germany and Pakistan. To the best of our knowledge this is the first report on the identification of O-desmethylnaproxen, the main metabolite of the drug naproxen, in environmental samples.