DETERMINATION OF ERYTHROMYCIN AND RELATED SUBSTANCES BY CAPILLARY ELECTROPHORESIS

Current compendial methods of assay for the analysis of erythromycin a nd its related substances involve the use of microbiological technique s. These techniques are non-selective and tedious, thus there is a nee d for the development of highly specific, quantitative analytical meth ods. Erythromycin was analysed in a 50 mM phosphate buffer (pH 7.5) an d run at an applied voltage of 20 kV. Detection sensitivity was enhanc ed by using a wavelength of 200 nm and selecting an injection solvent of lower conductivity than the electrolyte: acetonitrile-water (20:80, v/v). In order to facilitate the separation of erythromycin and its r elated substances, the organic solvent ethanol (35%, v/v) was incorpor ated into a modified 150 mM phosphate buffer (pH 7.5) and run at an ap plied voltage of 30 kV. Resolution of all the compounds was achieved i n approximately 45 min. The methods described are accurate and precise and thus suitable for the quantitative determination of erythromycin and the related substances, erythromycin C, anhydroerythromycin and N- demethylerythromycin A. (C) 1997 Elsevier Science B.V.