Journal of Chromatography A, 1203 (2008) 115–123 Contents lists available at ScienceDirect Journal of Chromatography A journal homepage: www.elsevier.com/locate/chroma Multi-residue determination of seven quinolones antibiotics in gilthead seabream using liquid chromatography–tandem mass spectrometry Victoria Samanidou a,∗ , Evaggelia Evaggelopoulou a , Martin Trötzmüller b , Xinghua Guo b , Ernst Lankmayr b a Aristotle University of Thessaloniki, Laboratory of Analytical Chemistry, GR-54124 Thessaloniki, Greece b Graz University of Technology, Institute of Analytical Chemistry and Radiochemistry, Technikerstrasse 4, 8010 Graz, Austria article info Article history: Received 9 April 2008 Received in revised form 26 June 2008 Accepted 2 July 2008 Available online 9 July 2008 Keywords: Quinolones Fish Gilthead seabream LC–MS/MS Residue analysis SPE abstract A sensitive and selective confirmatory analytical method for the multi-residue determination of seven quinolones (ciprofloxacin, enrofloxacin, sarafloxacin, danofloxacin, oxolinic acid, nalidixic acid and flume- quine) in gilthead seabream (Sparus aurata) was developed. The sample pre-treatment involves extraction with 0.1 M NaOH and purification by solid-phase extraction (SPE) on Waters Oasis HLB cartridges followed by the determination of all compounds in a single LC–electrospray ionization MS/MS run. Separation was achieved on a Perfectsil ODS-2, 5 m, 250 mm × 4 mm, analytical column (MZ Analysentechnik) by gra- dient elution using a mixture of 0.2% (v/v) formic acid, methanol and acetonitrile within 30 min. Multiple reaction monitoring (MRM) was used for selective detection of each quinolone. Accuracy was evaluated through recovery studies at three different fortification levels. The mean recoveries are between 90 and 132% for the selected levels with RSD values lower than 20%. The method presents satisfactory results for linearity, precision and limits of quantification. The latter are much lower than the maximum residue limits (MRLs) established by the European Union for quinolones in fish tissues (6–8 g/kg). © 2008 Published by Elsevier B.V. 1. Introduction The extensive administration of antibiotics in aquaculture has become a serious problem as their residues can persist in fish and sea-food. Antibiotics may be directly toxic or be the source of resistant human pathogens representing a possible risk to human health. For these reasons regulatory agencies have enacted deci- sions that keep these substances in aquaculture under control. This requires monitoring of antibiotic residues [1,2]. Quinolones constitute the main group of antibiotics used both in human and veterinary medicine for therapeutic purposes as effec- tive against Gram-negative bacteria. In fish farm industries they are used for the treatment of the generalized processes of septi- caemia or of skin diseases. The mechanism of action of quinolones is bactericidal; in most cases they inhibit the DNA enzyme gyrase of the bacteria cell, which is indispensable in the duplication of DNA. However their extensive administration to fish destined for human consumption, may lead to residues in edible tissues [3–5]. In order to protect human health from the potentially harmful antibiotic residues, the European Union (EU) has established max- ∗ Corresponding author. Tel.: +30 2310997698; fax: +30 2310997719. E-mail address: samanidu@chem.auth.gr (V. Samanidou). imum residue limits (MRLs) for substances authorized for use as veterinary drugs in food-producing animals (Council Regulation 2377/90/EEC) [6]. Technical guidelines and performance criteria for residue control, in the framework of the 96/23/EC Directive [7] are explained in the 657/2002/EC EU Commission Decision [8], concerning the performance of analytical methods for the determi- nation of organic residues and contaminants in living animals and animal products [4]. In literature analytical methods for the determination of quinolones in fish or sea food are mostly developed for a single analyte. HPLC is the separation technique of choice with vari- ous detection techniques: UV detection at 295 nm with limit of detection (LOD) 0.05 g/g [9], fluorescence detection with LODs from 1 to 15 g/kg [5,10–15] the LOD values reported were in the range of 1–15 g/kg as well as chemiluminescence detection based on the chemiluminescent enhancement by quinolones of the Ce(SO 4 ) 2 –Ru(bpy) 3 2+ –HNO 3 system with LODs from 0.36 to 2.4 g/kg [16]. Other analytical techniques include Capillary electrophoresis with UV detection (254 nm) [17] or mass spectrometric analysis with LODs of 20 g/kg [4], as well as an immunochemical-based multi-residue screening method (enzyme-linked immunosorbent assay, ELISA) described for fifteen (fluoro)quinolones residues at levels lower than the established MRLs. The latter cannot identify 0021-9673/$ – see front matter © 2008 Published by Elsevier B.V. doi:10.1016/j.chroma.2008.07.003