Determination of irbesartan in the presence of hydrochlorothiazide by derivative spectrophotometry

A first-derivative spectrophotometric method for the determination of irbesartan (IRB) alone and in the presence of hydrochlorothiazide (HCT) is described. Measurements are made at the zero-crossing wavelength at 263.0 nm for IRB. The calibration graph was linear over the range 1.0–12.0 mg l−1 of IRB, detection limit was 0.15 mg l−1. HCT, in the presence of IRB was determined by direct spectrophotometric method at 317 nm. The calibration graph was linear over the range 2.0–50.0 mg l−1 of HCT, detection limit was 0.25 mg l−1. The proposed methods were successfully applied to the determinations of IRB and HCT in combined tablets.