Determination of macrolide antibiotics in meat and fish by liquid chromatography–electrospray mass spectrometry

A simple and reliable method using liquid chromatography–electrospray ionization-mass spectrometry (LC–ESI-MS) has been developed for the determination of macrolide antibiotics, erythromycin (EM), oleandomycin (OM), kitasamycin (KT), josamycin (JM), mirosamicin (MRM), spiramycin (SPM), tilmicosin (TLM) and tylosin (TS) in meat. The LC separation was performed on a TSKgel Super ODS column ( 100 mm×2 mm i.d.) with a gradient system of 0.2% acetic acid–acetonitrile (containing 0.2% acetic acid) as the mobile phase at the flow rate of 0.2 ml/min. The positive ionization produced the molecular related ions, (M+2H) 2+, at m/ z 422 and 435 for SPM and TLM, and (M+H) +, at 734, 688, 772, 828, 728 and 916 for EM, OM, KT, JM, MRM and TS, respectively. The calibration graphs for each drug were rectilinear from 0.05 to 25 ng with selected ion monitoring (SIM). The drugs were extracted with 0.2% metaphosphoric acid–methanol (6:4), and the extracts were cleaned up on an Oasis HLB cartridge (60 mg). The recoveries of the drugs from meat and fish fortified at the 0.2 μg/g level was 70.4–93.2% with high precision. The limits of quantification of the drugs in meat and fish were 0.01 μg/g.