Indirect Spectrophotometric Method for the Quantitative Estimation of Tetracycline Hydrochloride in the Pharmaceutical Formulations

Abstract

       The objective of this work was to create an easy, fast, and accurate spectrophotometric approach for the assaying tetracycline hydrochloride in the bulk and in its pharmaceutical dosage forms. In this recommended approach tetracycline hydrochloride was oxidized with a known excess of an oxidant reagent N-bromosucinimide in an acidic medium and the excess of oxidant N-bromosucinimide was then reduced by indigo carmine dye and the absorbance of the residual indigo carmine dye was measured at wavelength of 610 nm. All the variables which affecting the conditions such as, influence of the amount of the oxidant, indigo carmine dye, acid concentration, oxidation time and the concentration limits of Beer׳s law were adjusted and studied carefully. The optimal conditions showed the color of the product solution was stable for more than 30 minutes. The standard calibration curve was linear in the variety of concentrations from 0.2 to 4.5 µg/ml of tetracycline hydrochloride with a good determination coefficient (R²) 0.9985 and molar absorptivity of 7.7190×10⁴ l/mol.cm. The LOD and LOQ values were evaluated and instituted to be 0.0043 and 0.0142 µg/ml, respectively. The suggested approach was successfully used to assay tetracycline hydrochloride in the available dosage forms, such as capsules and skin  ointment. The precision (RSD) was calculated and found  to be better than 0.721 %, whereas the values of recovery percent and relative errors were in the range of 99.76% to 100.33% and -0.45% to 0.48% respectively, without interfering from any common excipients.