COLLABORATIVE STUDY OF THE ANALYSIS OF ERYTHROMYCIN BY LIQUID-CHROMATOGRAPHY ON WIDE-PORE POLY(STYRENE-DIVINYLBENZENE)

A previously established method for analysis of erythromycin and related substances by liquid chromatography using a wide-pore poly(styrene-divinylbenzene) stationary phase was examined in a multicentre study involving 6 laboratories and a total of 7 columns. Three erythromycin samples were analysed. The main component and the impurities were determined. An analysis of variance treating each column as a different laboratory, showed absence of consistent laboratory bias and of laboratory-sample interaction. Estimates for the repeatability and reproducibility of the method, expressed as relative standard deviation (RSD) of the result of the determination of erythromycin A, were calculated to be 1.1 % and 1.3 % respectively.