Instrumental determination of certain antihypertensive drugs in pharmaceutical preparations

A- development and validation of the assay of four angiotensin-II-receptor antagonists in presence of hydrochlorothiazide by a gradient manner by reversed phase high performance liquid chromatography in their pharmaceutical formulations was performed by reversed phase high performance liquid chromatography using a mobile phase 0.025 M potassium dihydrogen phosphate (pH=6.0): acetonitrile isocratic(65:35v/v) or gradient (20:80v/v) with detection at 220 nm on a ACE C18 column(250 mm × 4.6 mm, 5 μm ) at flow rate 1.5 ml/min.B- Development and validation of a HPLC method for the assay of three angiotensin-II-receptor antagonists such as losartan potassium, irbesartan and telmisartan in presence of hydrochlorothiazide by an isocratic technique was performed by reversed phase high performance liquid chromatography using a mobile phase 0.025 M potassium dihydrogen phosphate (pH 6.0): acetonitrile with detection at 220 nm on a BDS Hypersil C18 column (250 mm × 4.6 mm, 5 μm) at flow rate 1.4 ml/min.Part 3:Development and validation of a HPLC method for the assay of telmisartan, ramipril, amlodipine besylate and atorvastatin calcium was performed by reversed phase high performance liquid chromatography using a mobile phase 0.025 M potassium dihydrogen phosphate (pH 6.0): acetonitrile with detection at 205 nm on a Hypersil BDS C18 column (250 mm × 4.6 mm, 5 μm) at flow rate 1.5 ml/min.Part 4:Development and validation of a HPLC method for the assay of amlodipine besylate, losartan potassium, valsartan and atorvastatin calcium was performed by reversed phase high performance liquid chromatography using a mobile phase 0.01 M ammonium acetate buffer (pH 3.5): acetonitrile with detection at 240 nm on a spherical monomeric C18 column (250 mm × 4.6 mm, 5 μm) at flow rate 1.5 ml/min.Part 5:A) Introduction to pharmaceutical Stress Testing (definitionand conditions).B) Validation of stability indicating HPLC method to stress degradation studies and simultaneous determination of several angiotensin-II-receptor antagonists (losartan potassium, irbesartan, valsartan and telmisartan) in presence of its chemical degradation products resulting under drastic conditions e.g. acidic degradation (HcL), alkaline degradation (NaoH),oxidation by (H2O2),exposing to heat equals to 70 C or exposing to light providing an overall illumination of not less than 1.2 million lux hour. It was found that Irbesartan was hydrolyzed under alkaline conditions ( at 70 C) and Losartan potassium and Valsartan were hydrolyzed under acidic conditions ( at 70 C) unlike Telmisartan was un affected by any conditions. This work was performed by an isocratic reversed phase high performance liquid chromatography using a mobile phase 0.025 M potassium dihydrogen phosphate(pH 6.0) : acetonitrile (65:35v/v) with detection at 220 nm on a ACE C18 column (250 mm × 4.6 mm, 5 μm ) at flow rate 1.5 ml/min .