Development and validation of spectrophotometric and ion pair chromatographic techniques for estimation of telmisartan and hydrochlorothiazide

Ultraviolet spectrophotometric and ion pair chromatographic methods have been developed for simultaneous estimation of telmisartan and hydrochlrothiazide from their tablet dosage form. The first method involves multiwavelength spectrophotometric estimation (Method 1) where interference due to hydrochlrothiazide at 286 nm (wavelength for estimation of telmisartan) was eliminated by recording absorbance difference at 286 nm and 308 nm whereas interference of telmisartan at 262 nm (wavelength for estimation of hydrochlrothiazide) was removed by recording absorbance difference at 262 nm and 282 nm. Linearity of the response was demonstrated by telmisartan in the concentration range of 5-35 μg/ml with a square correlation coefficient (r2) of 0.9995. Linearity of the response was demonstrated by hydrochlrothiazide in the concentration range of 3-21 μg/ml with a square correlation coefficient (r2) of 0.9992. The second method utilizes ion pair chromatography (Method 2) on a HIQ sil ODS column (250 mm length x 4.6 mm internal diameter) using methanol: 0.0025 M orthophosphoric acid (70:30 by volume pH 4.6) containing 0.1% 1-hexane sulphonic acid monohydrate sodium salt as mobile phase with UV detection at 259 nm over a concentration range of 20-120 μg/ml for telmisartan and 12.5-75 μg/ml for hydrochlrothiazide. Losartan potassium was used as the internal standard. Both the methods were applied successfully for the analysis of the two drugs from their tablet dosage form. The results of analysis were validated statistically and as per ICHQ2B guidelines. The developed methods are simple, selective and reproducible and can be applied for routine analysis of formulations containing telmisartan and hydrochlrothiazide