STUDY OF THE STABILITY OF ERYTHROMYCIN IN NEUTRAL AND ALKALINE-SOLUTIONS BY LIQUID-CHROMATOGRAPHY ON POLY(STYRENE-DIVINYLBENZENE)

A liquid chromatography method using poly(styrene-divinylbenzene) as t he stationary phase was used as the analytical method to investigate t he stability of the macrolide antibiotic erythromycin in neutral and a lkaline solutions (pH 7.5-11). Decomposition of erythromycin A was mon itored up to 20% of degradation. Three degradation products were detec ted: pseudoerythromycin A enol ether, pseudoerythromycin A hemiketal a nd a hydrolysis product of erythromycin A, i.e., the product with an o pened lactone structure. The decomposition kinetics have been studied as a function of the ionic strength, the concentration of the buffer, the amount of methanol in the solvent and the temperature.