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ABSTRACT
A quantitative evaluation of a toxic degradation component of tetracycline, the 4-epianhydrotetracycline, has been performed on samples produced in Brazil. Thirty one commercial samples of tetracycline hydrochloride and phosphate capsules from 11 pharmaceutical laboratories were analyzed. The determination was performed by HPLC as recommended by the U.S. Pharmacopeia. The suitability tests resulted in a chromatographic system condition with a 1.2 mL/min of the mobile phase, consisting of 0.09 M ammonium oxalate, dimethylformamide and 0.18 M ammonium dibasic phosphate (63.9 : 32 : 4.7). The resolution between 4-epianhydrotetracycline and tetracycline peaks was 3.7. The limits of detection and quantification were, respectively, 0.2 ng and 0.10 µg/mL. The calibration curve presented a correlation coefficient of 0.9999. Replicas of analysis revealed the reproducibility of the method. The results of the quantitative determination show coefficient of variation from 0.2 to 13.2%. All analyzed samples presented values below the specified limit for 4-epianhydrotetracycline hydrochloride, with a maximum quantity of 0.7%.