Separation of erythromycin and related substances on base-deactivated reversed-phase silica gel columns

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.