Abstract: Objective To establish an HPLC method for determination of the content of erythromycin cyclocarbonate (EMC) tablets. Methods EMC tablets were grinded and extracted with acetonitrile. The chromatographic separation was performed on a Waters Xbridge C₁₈ column (250 mm×4.6 mm, 5μm) with an isocratic elution system composed of 0.02 mol·L^-1 potassium hydrogen phosphate solution (adjust pH to 11.4 with 5 mol·L^-1 potassium hydroxide solution)-acetonitrile (35 : 65) at a flow rate of 1.0 mL·min^-1. The elutes were detected at the wavelength of 204 nm. Results A good linearity (r=0.9999) was observed within the range of 0.51 to 1.52 mg·mL^-1. The recovery was between 99.0% and 100.5% (RSD=0.5%, n=9), the repeatability was 0.8% (n=6), and the intermediate precision was 0.9% (n=12). The test and standard sample solution remained stable for 10 hours at 5℃, and the method showed good durability. The contents of the three batches of EMC tablets were 102.3%, 102.0% and 103.5% respectively, which were within the current standard limit range of 93.0% to 107.0%. Conclusion This method is simple, rapid, accurate and specific, and is workable for the content determination of EMC tablets. A reference method has become available for the in-depth study of EMC and for the analysis of compounds with tautomeric structure by liquid chromatography.

Key words: erythromycin cyclocarbonate, tautomerism, assay, HPLC