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ABSTRACT
Two new methods for the simultaneous determination of valsartan and hydrochlorothiazide in pharmaceutical dosage forms have been developed. 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 compensation of either component in the mixture can be achieved, followed by its determination. The second method, differential derivative spectrophotometry, comprised of measurement of the difference absorptivities derivatized in the first order (ΔD 1) of a tablet extract in 0.1 N NaOH relative to that of an equimolar solution in methanol at wavelengths of 227.8 and 276.5 nm, respectively. Neither sample pre-treatment nor separation were required. These methods showed good linearity, precision, and reproducibility. The results obtained were compared with the results of reversed phase HPLC. It was found that the difference was not statistically important between these methods. The proposed methods were accurate, sensitive, precise, reproducible and could be applied directly and easily to the pharmaceutical preparations.