Determination of erythromycin and related substances in enteric-coated tablet formulations by reversed-phase liquid chromatography.
An isocratic method for the identification and quantitation of erythromycin and related substances in enteric-coated tablet formulations using high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection at 205 nm is described. A novel method for sample preparation using a molecular weight centrifuge filter to reduce the interferences observed from polymeric tablet coating material is also presented. Erythromycin HPLC assays are best run at high pH; therefore, various polymer columns were evaluated. The resulting HPLC method that was developed has several advantages over current pharmacopeial assay methods for enteric-coated erythromycin tablets. Comparative data from both methods for the same batch of EryTab tablets are presented. The method can also be applied to various other erythromycin formulations, including particle-coated tablets, erythromycin stearate tablets, and erythromycin ethylsuccinate suspensions and fermentation broths. A C18 Polymeric column is used with a mobile phase composition of 0.02 M potassium phosphate dibasic buffer (pH 9): acetonitrile (60:40) and flow rate of 1 mL/min. This method is more sensitive, specific, and rugged than the pharmacopeial method.