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An official liquid chromatographic method for the analysis of erythromycin and related substances, which is based on a polymer reversed-phase, is described in the European Pharmacopoeia and in the United States Pharmacopeia. The pH of the mobile phase used in this system is 9.0. Recent advanced technology has led to the introduction of a new generation of silica-based reversed-phase column packings, which are claimed to be much more stable towards bases. They are useful for the analysis of basic compounds. Studies to verify the separation of erythromycin and related substances on Hypersil BDS C18, Luna C18(2), Inertsil ODS-2 and Supelcosil ABZ+ have been performed and the results are presented. It is shown that these base-deactivated phases give a better sensitivity and selectivity towards erythromycins than the polymer phase, provided that an adapted mobile phase is used. This is the first liquid chromatographic method described for the separation of erythromycin D from erythromycin A.

A selective reversed phase liquid chromatography/mass spectrometry (LC/MS(n)) method is described for the identification of erythromycin impurities and related substances in commercial erythromycin samples. Mass spectral data are acquired on a LCQ ion trap mass spectrometer equipped with an electrospray interface operated in positive ion mode. The LCQ is ideally suited for identification of impurities and related substances because it provides on-line LC/MS(n) capability. Compared with UV detection, this hyphenated LC/MS(n) technique provides as a main advantage efficient identification of novel substances without time-consuming isolation and purification procedures. Using this method four novel related substances were identified in commercial samples., (Copyright 2000 John Wiley & Sons, Ltd.)

A simple, sensitive, selective and robust isocratic LC method is described for the analysis of erythromycin on XTerra RP18. The main component, erythromycin A, is separated from all known related substances and degradation products. Several unknown impurities are also separated. Acetonitrile-0.2 MK2HPO4pH7.0-water, (35∶5∶60, v/v) was used as a mobile phase at 1.0 mL min−1. UV detection was at 215 nm. The robustness of the method was evaluated by a full-factorial experimental design. [ABSTRACT FROM AUTHOR]