Investigation of unknown related substances in commercial erythromycin samples with liquid chromatography/mass spectrometry

A selective reversed phase liquid chromatography/mass spectrometry (LC/MSn) method is described for the identification of erythromycin impurities and related substances in commercial erythromycin samples. Mass spectral data a re acquired on a LCQ ion trap mass spectrometer equipped with an electrospr ay interface operated in positive ion mode. The LCQ is ideally suited for i dentification of impurities and related substances because it provides on-l ine LC/MSn capability. Compared with UV detection, this hyphenated LC/MSn t echnique provides as a main advantage efficient identification of novel sub stances without time-consuming isolation and purification procedures. Using this method four novel related substances were identified in commercial sa mples. Copyright (C) 2000 John Wiley & Sons, Ltd.