Development of a new sample pretreatment procedure based on pressurized liquid extraction for the determination of fluoroquinolone residues in table eggs

A new method for the simultaneous determination of three fluoroquinolones (FQs) enrofloxacin (ENRO) ciprofloxacin (CIPRO) and sarafloxacin (SARA) in table eggs has been developed, applying pressurized liquid extraction (PLE) and liquid chromatography (LC) with fluorescence detection (LC-FLD). The influence of several extraction parameters (e.g. solvent mixture, temperature and extraction time) on FQs extraction efficiency and coextracted matrix interferents was evaluated using fortified control eggs and matrix matched standard curves. The results showed that FQs extraction efficiency depends mainly on solvent composition and the optimum extraction mixture was found to be phosphate 50 mM, pH 3.0/acetonitrile (50:50, v/v). The optimized procedure employed 50% flush volume, 5 min of static time and three extraction cycles at 70 °C and 1500 psi. Method validation was performed according to the guidelines of the Directive 96/23/EC, using control egg samples, fortified with the target FQs in the range 50–1000 ng g−1 and applying the optimized extraction conditions on three different days, providing recoveries between 67–90% with RSDs lower than 11% in all cases. The decision limit (CCα) and detection capability (CCβ) of the analytical method were found to be within the range 17–24 ng g−1 and 30–41 ng g−1, respectively. The method was successfully applied to the determination of ENRO and its metabolite CIPRO in incurred egg samples from ENRO-treated hens and LC–MS has been used and for confirmatory purposes.