Determination of macrolide antibiotics in milk by high-performance liquid chromatography/mass spectrometry

A simple and reliable method using liquid chromatography electrospray ionization-mass spectrometry (LC/ESI-MS) has been developed as an analytical method of macrolide antibiotics, such as erythromycin, oleandmycin, kitasamycin, josamycin, mirosamicin, neospiramycin, spiramycin, tilmicosin and tylosin in milk. The drugs were extracted with acetonitrile, and the extracts were cleaned up by partition with hexane. The extracts were analyzed using LC/MS. The LC separation was performed on a TSK-gel Super ODS column (100 mm X 2 mm i.d.) with a gradient system of 0.2% acetic acid-acetonitrile as the mobile phase. MS acquisitions parameters were established in the positive ESI mode, and the related molecular ions were (M + 2H)(2+) or (M + H)(+). The recoveries of the drugs from milk fortified at a level 0.1 mu g/g were 63.8 similar to 95.9% with high precision. The limits of detection of the drugs in milk were 0.01 mu g/g.