Determination of roxithromycin residues in the flounder muscle with electrospray liquid chromatography–mass spectrometry

A highly sensitive and specific method for the determination of roxithromycin in the flounder muscle by LC–MS was developed and validated. A dichloromethane extract of the sample was separated on C18 reversed-phase column with acetonitrile–50 mM ammonium acetate (80:20, v/v) as the mobile phase and analyzed by LC–MS via atmospheric pressure ionization/electrospray ionization interface. The limit of detection and limit of quantitation were 0.01 and 0.1 ng/g, respectively. Mean recoveries from spiked muscles were 81.1% (ranged from 71.0 to 90.3%) for roxithromycin. The method has been successfully applied to determine roxithromycin in the flounder muscle.