A simple, rapid, and precise method is developed for the quantitative simultaneous estimation of telmisartan and hydrochlorothiazide in combined pharmaceutical dosage form. A chromatographic separation of the two drugs was achieved with an ACE 5 C 18 (250 x 4.6 mm) analytical column using buffer-acetonitrile (55:45 v/v). The buffer used in mobile phase contains 0.1M sodium perchlorate monohydrate in double distilled water pH adjusted 3.0 with trifluoroacetic acid. The instrumental settings are

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... low rate of 1.5 ml min -1 , column temperature at 30 o C, and detector wavelength of 215 nm using a photodiode array detector. The resolution between hydrochlorothiazide and telmisartan founds to be more than 5. Theoretical plates for hydrochlorothiazide and telmisartan were 13022 and 6629 respectively. Tailing factor for hydrochlorothiazide and telmisartan was 0.94 and 0.98 respectively. Telmisartan, hydrochlorothiazide and their combination drug products stressed samples were analysed by the proposed method. The described method shows excellent linearity over a range of 70 to 130% of target analyte concentration. The correlation coefficient for telmisartan and hydrochlorothiazide are 0.9999. The relative standard deviation for six measurements in two sets of each drug in tablets is always less than 2%. The proposed method was found to be suitable and accurate for quantitative determination and stability study of telmisartan and hydrochlorothiazide in pharmaceutical preparations.