DETERMINATION OF ERYTHROMYCIN ETHYLSUCCINATE AND ITS RELATED SUBSTANCES BY ION SUPPRESSION CHROMATOGRAPHY

AIM　To develop a method for the determination of erythromycin ethylsuccinate (EES) and its related substances by ion suppression chromatography (ISC), and investigate the influence factors on ISC. METHODS　A Zorbax SB-C₁₈ column was used. The mobile phase was 0.02 mol.L^-1 KH₂PO₄-acetonitrile (45∶55, adjusted to pH 6.8 with aqueous ammonia) and the flow rate was 1.2 mL.min^-1. The UV detection wavelength was 210 nm. The column temperature was maintained at (30±0.5)℃. RESULTS　The composition of mobile phase showed the greatest influence on retention and selectivity, EES was relatively stable in acetonitrile. The main component, erythromycin A ethylsuccinate and its related substances were separated and assayed by ISC, the average recovery of erythromycin A ethylsuccinate was 99.45% (RSD=2.24%, n=5). CONCLUSION　The method can be used to analyze EES.