Colourimetric Method for Assaying Tetracycline Hydrochloride in Pharmaceutical Formulations via Zirconium Complex Formation

Abstract

This paper includes development of a sensitive, accurate and precise direct spectrophotometric approach to estimate tetracycline hydrochloride in the bulk solution and in its pharmaceutical preparations. The method was based on the reaction of tetracycline hydrochloride with zirconium (IV) in presence of acetate buffer solution at pH3.6 to form a yellow complex with a highest absorption peak at 398 nm. The resulting complex conforms Beer's law to cover the concentration in the range of 0.5 to 12.5 µg/ml with a good determination coefficient (r2 =0.9989), molar absorptivity of 2.7798×104 l/mol.cm and Sandell's sensitivity of 0.0173 μg/cm2 . The Limits of detection (LOD) and quantitation (LOQ) were equal to 0.019 and 0.063μg/ml, respectively. A relative standard deviation (precision) was evaluated to be better than 0.91% depending on the concentration levels, whereas the value of recovery percentage were in the range of 97.20% to 103.82%. The approach was useful to the analysis of tetracycline hydrochloride in capsules and skin ointment. The statistic factors t-test and F-test values have also been investigated and revealed that the experimental "t" and "F" results were less than the theoretical results at confidence level of 95%