Abstract: Aim Method for the determination of erythromycin ethylsuccinate(EES) by ion suppression chromatography (ISC) was developed and the influenc factors on ISC were investigated. Methods A Zorbax SB-C18 column was used with 0.02 mol·L^-1 potassium dihydrogen phosphate acetonitrile (45:55) as mobile phase. The pH and proportion of the mobile phase showed the greatest influences on retention and selectivity. Therefore, the pH of mobile was adjusted to 6.8, the best acetonitrile proportion was 55%. The column temperature was maintained at (30±0.5) °C. Acetonitrile was used as solvent for the sample preparation because EES is more stable in it. The flow rate was 1.2 mL·min^-1 and UV detection was performed at 210 nm. Results Under these chromatographic conditions, the main component (erythromycin A ethylsuccinate) and its related substances were separated. The calibration curve showed good linearity over the range of 0.1-1.0 mg·mL^-1, and its correlation coefficient was 0.9998. Conclusion The method is very suitable for the analysis of erythromycin ethylsuccinate.

Key words: erythromycin ethylsuccinate, erythromycin ethylsuccinate, related substances, related substances, ion suppression chromatography, ion suppression chromatography, method development, method development