Journal of Chromatography B, 745 (2000) 325–332 www.elsevier.com / locate / chromb Enantioselective analysis of levetiracetam and its enantiomer R-a-ethyl-2-oxo-pyrrolidine acetamide using gas chromatography and ion trap mass spectrometric detection a c d b,e c Nina Isoherranen , Michael Roeder , Stefan Soback , Boris Yagen , Volker Schurig , a,e, * Meir Bialer a Department of Pharmaceutics, The Hebrew University of Jerusalem, Jerusalem, Israel b Department of Medicinal Chemistry and Natural Products, The Hebrew University of Jerusalem, Jerusalem, Israel c ¨ ¨ Institute of Organic Chemistry, University of Tubingen, Tubingen, Germany d Kimron Veterinary Institute, National Residue Control Laboratory, Beit Dagan, Israel e The David R. Bloom Center for Pharmacy, Jerusalem, Israel Received 27 January 2000; received in revised form 16 May 2000; accepted 17 May 2000 Abstract A gas chromatographic–mass spectrometric method was developed for the enantioselective analysis of levetiracetam and its enantiomer ( R)-a-ethyl-2-oxo-pyrrolidine acetamide in dog plasma and urine. A solid-phase extraction procedure was followed by gas chromatographic separation of the enantiomers on a chiral cyclodextrin capillary column and detection using ion trap mass spectrometry. The fragmentation pattern of the enantiomers was further investigated using tandem mass spectrometry. For quantitative analysis three single ions were selected from the enantiomers, enabling selected ion monitoring in detection. The calibration curves were linear from 1 mM to 2 mM for plasma samples and from 0.5 mM to 38 mM for urine samples. In plasma and urine samples the inter-day precision, expressed as relative standard deviation was around 10% in all concentrations. Selected ion monitoring mass spectrometry is suitable for quantitative analysis of a wide concentration range of levetiracetam and its enantiomer in biological samples. The method was successfully applied to a pharmacokinetic study of levetiracetam and (R)-a-ethyl-2-oxo-pyrrolidine acetamide in a dog.  2000 Elsevier Science B.V. All rights reserved. Keywords: Enantiomer separation; Levetiracetam; R-( a)-ethyl-2-oxo-pyrrolidine acetamide 1. Introduction Chirality is a cardinal issue in modern pharma- ceutical sciences. During design and development of *Corresponding author. Faculty of Medicine, Department of chiral drugs one must decide between development Pharmaceutics, School of Pharmacy, The Hebrew University of of racemic form of a drug or an enantiospecific form Jerusalem, P.O. Box 12065, Jerusalem, Israel. Tel.: 1972-2-6758- [1]. Enantioselective assays are essential for drug 610; fax: 1972-2-6757-246. E-mail address: bialer@md2.huji.ac.il (M. Bialer). development since isomeric impurities may have 0378-4347 / 00 / $ – see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0378-4347(00)00293-0