COLORIMETRIC DETERMINATION OF MACROLIDE ANTIBIOTICS USING FERRIC ION

Macrolide antibiotics such as erythromycin, oleandomycin, spiromycin, and tylosin are found to react with Fe3+ in the presence of an acetic acid-sulfuric acid mixture to form a colored product having a useful a bsorption band at 592 nm. Troleandomycin forms only a weakly colored p roduct upon reaction. The molar absorptivity is about 2900 l mol(-1) c m(-1) for erythromycin and the detection limit is 5 mu g ml(-1). This colorimetric method permits the analysis of fermentation broths contai ning either erythromycin or tylosin without a separation step.