Three new spectrophotometric methods applied to the simultaneous determination of hydrochlorothiazide and irbesartan

This work involves the simultaneous determination of hydrochlorothiazide and irbesartan in a binary mixture without previous separation by three new analytical methods. The first method, based on compensation technique, is presented for the derivative spectrophotometric determination of binary mixtures with overlapping spectra. By using ratios of the derivative maxima or the derivative minimum, the exact contribution of either component in the binary mixture can be measured and the amounts quantified. The second method uses of the first derivative of the ratio spectra. The ratio spectra were obtained by dividing the absorption spectra of the binary mixture by that of one of the components. The amplitudes in the first derivative of the ratio spectra at 231, 266, 279, 238 and 248 nm were selected to determine hydrochlorothiazide and irbesartan in binary mixtures. The concentration of the other components are then determined from their respective calibration graphs treated similarly. With the third method, the absorbance ratio method, the determination of hydrochlorothiazide and irbesartan was performed using the absorbances read at 272 nm, 241 nm and 263 nm in the zero-order spectra of their mixture. The absorbance ratio was also developed as a comparison method. The three methods are simple, accurate, rapid and require no preliminary separation steps and can, therefore, be used for routine analysis of both drugs in quality control laboratories.