Determination of Erythromycin and Oleandomycin in Meat and Fish by LC/MS

A simple and rapid method using liquid chromatography-electrospray ionization-mass spectrometry (LC/MS-ESI) has been developed for the determination of macrolide antibiotics, erythromycin and oleandomycin, in meat and fish. The LC separation was carried out on a TSK-gel ODS 80-Ts column (150×2mm) by using 0.1% acetic acid-acetonitrile (65:35) as the mobile phase at a flow rate of 0.2mL/min. The positive ionization produced typical (M+H)+ molecular ions of both drugs (erythromycin m/z 734; oleandomycin m/z 688). The calibration graphs for erythromycin and oleandomycin were rectilinear from 0.05 to 10ng with selected ion monitoring (SIM). The drugs were extracted with 0.1% metaphosphoric acid-methanol (5:5), and the extracts were cleaned up on an OASIS HLB cartridge (60mg). The recoveries of the drugs from meat and fish fortified at a level of 0.2μg/g were 79.4-95.4%, with high precision. The limits of quantification of both drugs in meat and fish were 0.01μg/g.