Analysis of tetracycline in pharmaceutical preparations by improved high-performance liquid chromatographic method

The analysis of tetracycline in pharmaceutical preparations by an improved high-performance liquid chromatographic (HPLC) method is described. The improved method uses a 30-cm long stainless steel column packed with octadecylsilane bonded on 10-mum silica gel, with a linear gradient from 10 to 60% acetonitrile in pH 2.5, 0.02 M phosphate buffer in 11 min at a flow rate of 1.0 ml/min (68 atm). The resolution functions obtained between 4-epitetracycline and tetracycline and between 4-epianhydrotetracycline and anhydrotetracycline were improved 150 and 250%, respectively. The analysis of a tetracycline sample takes approximately 16 min; the original method required more tan 25 min. The relative standard deviation for the analysis of tetracycline powder was 0.66%, and the recovery of 4-epianhydrotetracycline added in tetracycline was linear over the 0.3-100% range. Recovery of tetracycline from products was better than 99.6% at label concentration. The drug content of products as calculated from the HPLC data agreed well with those of the microbiological assay methods.