Analysis and mass spectrometric characterization of the insect repellent Bayrepel and its main metabolite Bayrepel-acid

Insect repellents such as N,N-diethyl-m-toluamide (DEET) which are used as protection against mosquitoes or ticks were detected in all wastewater and anthropogenically influenced surface waters analyzed. In Germany, the concentrations of DEET have constantly decreased since 1999, when DEET was substituted by Bayrepel (1-piperidinecarboxylic acid, 2-(2-hydroxyethyl), 1-methylpropyl ester; KBR 3023) in commercial insect repellent formulations. A sensitive quantitative method was developed in order to study the occurrence and fate of Bayrepel in the aquatic environment. It was thus determined that Bayrepel undergoes rapid primary aerobic biodegradation, yielding a more stable metabolite, Bayrepel-acid (1-piperidinecarboxylic acid, 1-methylpropyl ester, 2-acetic acid). In order to study the biodegradation and investigate the fate of this metabolite, Bayrepel-acid was synthesized and characterized. Various chromatographic and mass spectrometric techniques, such as gas chromatography–mass spectrometry (MS) after derivatization, liquid chromatography (LC)–electrospray ionization (ESI) MS and LC–ESI time-of-flight MS were applied.