Torsemide Analysis Using Derivative Spectrophotometric Methods

Abstract

An accurate stability-indicating method has been developed for the analysis of Torsemide (TOR) in bulk and pharmaceutical dosage forms. The methods used the zero-order spectrum (⁰D) of TOR aqueous solution (measured at 285 nm) and the instrumentally differentiated first (¹D) and second (²D) derivative spectra (measured at 311 nm and 282 nm, respectively). The effect of light, acid (HCL) and alkali (NaOH) on the stability of TOR were studied using the new methods. ICH guidelines were used to validate the new methods. Regression analysis of Beer’s plots showed a good correlation coefficient not less than 0.998. These methods reported great inter-day and intra-day precision. Excipients interference was not detected due to the achievement of good recovery percentages (97.60 - 101.45 ± 2.7 %, n=3). Good assay results ranged from 99.0 ± 1.7% to 100.0 ± 2.5%; the developed methods obtained  n=3. The ²D model proved its ability to be used as a stability indication method of TOR analysis. TOR was unstable in acids and bases with or without heating. Its degradation follows the first-order kinetics. However, its aqueous solution was proved to be stable under sunlight. The established methods demonstrated good precision, sensitivity and accuracy at 95% confidence level.