Journal of pharmaceutical and biomedical analysis vol:6 issue:5 pages:461-72
Important interlaboratory variation was obtained for the water content of erythromycin samples as determined by the Karl Fischer method. It is demonstrated that the variation is related to the type of reagents used. In poorly buffered systems erythromycin enol ether and water are formed by acid degradation of erythromycin. However, when an appropriate solvent is used, accurate titration of water in erythromycin is possible. A 10% m/v solution of imidazole in methanol is preferred to pyridine or a mixture of pyridine and methanol for it has a good buffer capacity, it lacks the unpleasant odour of pyridine and it allows a high titration speed.