Spectrophotometric methods for simultaneous determination of Carvedilol and Hydrochlorothiazide in combined dosage form

In Method (I), two wavelengths were selected for each drug in such a way that the difference in absorbance is zero for the second drug. At wavelengths 238 and 248.8 nm HCT has equal absorbance values, therefore, these two wavelengths have been used to determine CV, on similar basis 266 and 289.4 nm were selected to determine HCT in the combined formulation. Method (II) involves the formation of Q-absorbance equation using the respective absorptivity values at 229.2 nm (isoabsorptive point) and 241 nm (λmax of CV). The drugs obey Beer's Lambert's law in the concentration range of 1-10 μg/mL for both CV and HCT (for Method I) and in the range of 1-10 and 2-10 μg/mL for CV and HCT, respectively (for Method II). The accuracy and precision were determined and recovery studies confirmed the accuracy of the developed methods that were carried out following the International Conference on Harmonization (ICH) guidelines. Statistical comparison of the suggested methods with the reported spectrophotometric one using F and t tests showed no significant difference regarding both accuracy and precision.