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GRADIENT HPLC-DAD DETERMINATION OF THE ANTIHYPERTENSIVE MIXTURE OF AMLODIPINE BESYLATE, VALSARTAN, AND HYDROCHLOROTHIAZIDE IN COMBINED PHARMACEUTICAL TABLETS

A triple drug combination of amlodipine besylate (AML), valsartan (VAL), and hydrochlothiazide (HCT) was recently approved by the European Medicines Agency and the FDA for the treatment of moderate and severe hypertension. In this work, a simple, rapid, and reliable HPLC-DAD method was described for the simultaneous determination of the three antihypertensives. Chromatographic separation was achieved using Zorbax SB-C8 column with gradient elution of the mobile phase composed of 0.025 M phosphoric acid and acetonitrile. The gradient elution started with 30% (by volume) acetonitrile, ramped up linearly to 70% in 3 min then kept constant for the remainder of the run. The flow rate was 1 mL/min. The multiple wavelength detector was set at 238 nm for measurement of AML and 225 nm for VAL and HCT. Quantification was based on measuring peak areas. The analytes were resolved with retention times 4.2, 4.7, and 6.5 min for HCT, AML, and VAL, respectively. Analytical performance of the proposed procedure was validated with respect to system suitability, linearity, ranges, precision, accuracy, robustness, detection, and quantification limits. The linearity ranges were 5–100, 2.5–200, and 2.5–100 µg/mL for AML, VAL, and HCT, respectively. The validated HPLC method was extended to the analysis of this combination in several laboratory-prepared mixtures of different ratios. Specificity was tested by resolution of the three analytes from several pharmaceutical compounds of various medicinal categories. Finally, Exforge HCT® tablets were assayed using the developed procedure where no interfering peaks were encountered from the tablet additives.