High-resolution LC/MS for analysis of minor components in complex mixtures: negative ion ESI for identification of impurities and degradation products of a novel oligosaccharide antibiotic

High-resolution mass spectrometry has been routinely used for structural co nfirmation and identification; however, it has mostly been applied to relat ively pure samples. Exact mass measurement of minor components such as impu rities, degradation products or metabolites in complex mixtures has been di fficult without prior separation and isolation, Here we report the utilizat ion of on-line liquid chromatography in combination with high-resolution ma ss spectrometry for the identification of impurities and base degradation p roducts of Sch 27899, a member of the everninomicin class of antibiotics. N ine Sch 27899-related impurities and degradation products were detected by negative ion electrospray ionization using a magnetic sector mass spectrome ter, Exact mass measurements were obtained at a resolution of 5000 using po lyethylene glycol (PEG) sulfates as internal standards. Corresponding eleme ntal compositions were determined within a 2 ppm error tolerance and struct ures were proposed for all components. Copyright (C) 2000 John Wiley & Sons , Ltd.