RP-LC and HPTLC Methods for the Determination of Olmesartan Medoxomil and Hydrochlorothiazide in Combined Tablet Dosage Forms

Two new, rapid, precise, accurate and specific chromatographic methods were described for the simultaneous determination of olmesartan medoxomil and hydrochlorothiazide in combined tablet dosage forms. The first method was based on reversed phase liquid chromatography using an Eurosphere 100 RP C18 column (250 × 4.6 mm ID, 5 μm). The mobile phase was methanol–0.05% o-phosphoric acid (60:40 v/v) at a flow rate of 1.0 mL min−1. Commercially available tablets and laboratory mixtures containing both drugs were assayed and detected using a UV detector at 270 nm. The second method involved silica gel 60 F254 high performance thin layer chromatography and densitometric detection at 254 nm using acetonitrile–ethyl acetate–glacial acid (7:3:0.4 v/v/v) as the mobile phase. Calibration curves ranged between 200–600 and 125–375 ng spot−1 for olmesartan and hydrochlorothiazide, respectively

Ratio Spectra Derivative and Zero-Crossing Difference Spectrophotometric Determination of Olmesartan Medoxomil and Hydrochlorothiazide in Combined Pharmaceutical Dosage Form

Two simple, economical, rapid, precise, and accurate methods for simultaneous determination of olmesartan medoxomil and hydrochlorothiazide in combined tablet dosage form have been developed. The first method is based on ratio spectra derivative spectrophotometry, and the second method is zero-crossing difference spectrophotometry. The amplitudes in the first derivative of the corresponding ratio spectra at 231.0 and 271.0 nm were selected to determine olmesartan medoxomil and hydrochlorothiazide, respectively. Measurements of absorbance were carried out at zero-crossing wavelengths 257.8 and 240.2 nm for olmesartan medoxomil and hydrochlorothiazide by zero-crossing difference spectrophotometric method. Beer’s law is obeyed in the concentration range of 08–24 µg/mL for olmesartan medoxomil (OLM) and 05–15 µg/mL for hydrochlorothiazide (HCT) by ratio spectra derivative and 05–30 µg/mL for OLM and HCT by zero-crossing difference spectrophotometric method. The results of the assay were found to be 100.46 ± 0.95 for OLM and 100.4 ± 0.27 for HCT by ratio spectra derivative and 99.06 ± 1.14 for OLM and 100.05 ± 0.90 for HCT by zero-crossing difference spectrophotometric method. These methods passes F test and t test. Both methods were validated statistically and by performing recovery study