Spectral Resolution of a Binary Mixture Containing Valsartan and Hydrochlorothiazide in Tablets by Ratio Spectra Derivative and Inverse Least Square Techniques

Abstract

Two new spectral approach (graphical and chemometric techniques) were applied for resolution of a binary mixture of valsartan (VST) and hydrochlorothiazide (HCT) in tablets without a separation procedure. In the ratio derivative spectrophotometry, analytical derivative amplitudes were measured at 231.5 and 260.5 nm for VST and at 270.6 nm for HCT in the first derivative of the ratio spectra. The calibration graphs follow Beer's law in the ranges of 8–24 µg mL⁻¹ for VST and 2–10 µg mL⁻¹ for HCT. The prepared calibrations for the first technique were tested for the synthetic binary mixtures of both drugs. Mean recoveries and relative standard deviations were found as 100.4% and 1.76% for VST, 102.5% and 2.41% for HCT, respectively. In the inverse least‐square technique, absorbances matrix were produced by measurements in the spectral range from 225 to 280 nm of the interval of Δλ = 5 nm at 12 wavelengths in zero order spectra of the various binary mixtures. The prepared calibration set for the absorbance and concentration values were used to predict the concentration of VST and HCT in their binary mixtures and tablets. The “Maple V” software was used for the numerical calculations. For this technique, mean recoveries and relative standard deviations were found as 101.2% and 1.58% for VST and 96.2% and 2.35% for HCT. Both techniques were successfully applied for the determination of these two drugs in tablets.

Keywords:

• Valsartan
• Hydrochlorothiazide
• Inverse least‐squares
• Ratio derivative spectrophotometry
• Determination

Acknowledgments

The authors gratefully acknowledge Novartis Pharm. Ind. for supplying valsartan and hydrochlorothiazide and its pharmaceutical preparation.