Synthesis and use of pentadeuteroethyl ethofumesate as an internal standard for the determination of ethofumesate and its metabolites in water by gas chromatography-mass spectrometry

Abstract Pentadeuteroethyl ethofumesate (ETO-d 5 ) was synthesized starting by acid hydrolysis of ethofumesate to 2,3-dihydro-2-hydroxy-3,3-dimethylbenzofuran-5-yl methanesulionate (ETO-OH) and successive ethylation with iodoethane-d 5 . This deuterated compound was used as an internal standard for the determination by gas chromatography-mass spectrometry in the selected-ion monitoring mode of ethofumesate (ETO) and its chief metabolites, ETO-OH and 2,3-dihydro-2-oxo-3,3-dimethylbenzofuran-5-yl methanesulfonate (ETO-K). The recovery of these substances by solid-phase extraction from drinking water was comparable to those with C 18 -bonded silica and Carbopack B phases. The recoveries of ETO and ETO-K were virtually complete, compared with 66% extraction for ETO-OH.