Determination of erythromycin and related substances in commercial samples using liquid chromatography/ion trap mass spectrometry

A sensitive, precise and accurate quantitative liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the measurement of erythromycin A (EA) and related substances in commercial samples was developed and validated. The samples were chromatographed on a reversed-phase column with a polar endcapping and analyzed by ion trap tandem mass spectrometry in the multiple reaction monitoring (MRM) mode using positive electrospray ionization. The method showed high recovery (>= 98.82%), high sensitivity (lower limit of quantitation of 0.25 ng/mL for EA and less than 7.3 ng/mL for the related substances) and high precision (<= 0.52%) as well as excellent linearity (r(2) > 0.991) with a run time of only 13 min. The method was successfully applied to the determination of EA and related substances in commercial samples. Moreover, using the advanced data-dependent acquisition capability of the ion trap software two new unexpected EA related substances could be detected and possible structures for these substances were postulated. (c) 2006 Elsevier B.V. All rights reserved.