Improved high-pressure liquid chromatographic method for the analysis of erythromycin in solid dosage forms.

A stability-indicating high-pressure liquid chromatographic (HPLC) method for the assay of erythromycin in enteric film-coated tablets was developed. The method used a reversed-phase column at 70 degrees with a mobile phase of acetonitrile-methanol-0.2 M ammonium acetate-water (45:10:10:35) at pH 7.0. The column were evaluated for the analysis of erythromycin. The HPLC method was also applicable for the analysis of salts and esters of erythromycin. The linearity and precision of the HPLC assay method for erythromycin in the solid dosage form were examined by spiking erythromycin into a tablet placebo a 60-120% of the label. The recovery of erythromycin was 99.9% with a relative standard deviation of less than 1%. The correction factors to express the results of HPLC in terms of antimicrobial bioequivalency against Staphylococcus aureus TCC 6538P for erythromycins A, B, and C were determined to be 1.0, 0.92, and 0.48, respectively. Eight lots of tablets were assayed by the HPLC method, and the results, expressed in terms of erythromycin bioequivalency, showed no statistically significant difference from those of the microbiological assay method.