Determination of tetracycline hydrochloride in presence of anhydrotetracycline by differential pulse polarography.

A differential pulse polarographic method is described for the determination of the antibiotic tetracycline HCl in the presence of its degradation product anhydrotetracycline. The method utilizes the large difference in their differential pulse polarograms at a peak potential of -1.39 V in 0.1 M phosphate buffer as the base electrolyte (pH 6.8). The assay was evaluated using synthetic mixtures and applied to the analysis of commercial tetracycline HCl samples. The results obtained with this method are in close agreement with those from the spectrophotometric absorbance ratio method.