Simultaneous determination of selected veterinary antibiotics in gilthead seabream (Sparus Aurata) by liquid chromatography-mass spectrometry.

A method was optimised and validated for simultaneous monitoring of several drugs of different classes of antibiotics such as quinolones (oxilinic acid and flumequine), tetracyclines (oxytetracycline), sulfonamides (sulfadiazine) and trimethoprim in fish muscle and skin. The method is based on solid-liquid extraction without further sample clean up followed by liquid chromatography-mass spectrometry (LC-MS) determination with electrospray ion source (ESI) in positive mode. The limits of quantification (LOQs) were lower than 20 microg/kg for all compounds and repeatability, expressed as relative standard deviations (RSD), were lower than 15%. Therefore, the LC-MS method was successfully applied for the quantitative determination of antibiotics in gilthead sea bream muscle and skin and oxytetracycline in medicated fishes.