Int. J. Pharm. Sci. Rev. Res., 24(2), Jan – Feb 2014; nᵒ 51, 311-314 ISSN 0976 – 044X International Journal of Pharmaceutical Sciences Review and Research Available online at www.globalresearchonline.net 311 Reem Youssef 1 * , Adnan Hbash 2 , Ahmad Hassan 3 1 Master Degree in Drug Quality Control, Faculty of Pharmacy, Damascus University, Damascus. 2 Professor in Faculty of science–Damascus University 3 Professor at the Dept of Pharmaceutical Chemistry and drug Quality Control, Faculty of Pharmacy, Damascus University, Damascus. * Corresponding author’s E-mail: dr.reem83@yahoo.com Accepted on: 10-12-2013; Finalized on: 31-01-2014. ABSTRACT A simple, rapid, and precise reversed-phase High performance liquid chromatographic (RP-HPLC) method has been developed and validated for the determination and separation of Valsartan, Losartan and Irbesartan in bulk and pharmaceutical dosage form. Chromatographic separation of these drugs was achieved on a reverse phase C18 column using a mobile phase consisting of acetonitrile: phosphate potassium buffer (pH= 3). The mobile phase was pumped at a flow rate of 1.5 mL/min and the eluents were monitored at 254 nm. The method was successfully validated in accordance to ICH guidelines acceptance criteria for (linearity, accuracy, precision, selectivity, limit of detection, limit of quantification) all validation parameters were within the acceptance range. The proposed method was found to be suitable and accurate for quantitative determination and separation of mixture of three drugs in bulk samples and pharmaceutical preparation and it can be used for the quality control of formulation products. Keywords: Estimation, Irbesartan, Losartan, RP-HPLC, Validation, Valsartan. INTRODUCTION here are new highly selective, non-peptide angiotensin II type 1(AT1)-receptor antagonist that lower blood pressure through blockade of the rennin angiotensin – aldosterone system (RAAS).They are widely used in treatment of Hypertension. 1-3 These drugs are called angiotensin receptor blockers (ARBs). They can selectively block the angiotensin II type 1 (AT1) receptors, causing inhibition of the action of angiotensin II on vascular smooth muscle, ultimately leading to a reduction in arterial blood pressure. It is useful in treatment of mild to moderate hypertension and well tolerated with lower incidence of cough than ACE inhibitors. 1-3 The drug substances studied in this research are: Valsartan, Losartan and Irbesartan, they are methyl biphenyl derivatives used as angiotentsin II antagonists. 4 Losartan potassium is (2-Butyl–4–chloro–1-[[2′-(1H- tetrazol-5- ylbiphenyl]-4–yl]methyl]-1H- imidazole–5– methanol. 4 Irbesartan is 2-Butyl–3-[[2′-(1H-tetrazol–5–yl)[1,1′- biphenyl]-4-yl]methyl]-1,3- diazaspiro[4.4] non–1–en –4– one. 4 Valsartan is n-[p-o-1h-tetrarazole-5-yl phenyl)benzyl-n- valeryl-L-valine. 4 These three drugs have similar chemical structures figure 1. M ATERIALS AND M ETHODS Reference standards of Irbesartan, Losartan and valsartan were obtained from sigma Aldrich Chemical Co. (Hamburg, Germany). -The pharmaceutical tablets sample was purchased from the Community Pharmacy. Chemicals and solvents Potassium dihydrogen phosphate and ortho phosphoric acid were obtained from BDH Laboratory Supplies (Poole) UK. HPLC Solvents (Acetonitrile, Methanol, water) were purchased from the Merck, Germany pH solutions: Hana company, Hungary. Instrument and Equipments JASCO high pressure liquid chromatography system provided with two pump (PU-980 Intelligent HP) and UV /VIS detector (UV 254 nm), and manual injector (20 μl loop).  An Ultrasonic device T310 Germany  pH meter model Orion 410 A  Magnetic stirrer model Labinco L33  Filters 0.45 μm from Whatman Inc.  HPLC filters 0.45 μm from Sartorius stedium biotech company.  C8 column (250X4.6) mm Eurospher, 5μm from - Knauer Germany. Irbesartan Development and Validation of RP-HPLC M ethod for the Estimation and Separation of Valsartan, Losartan and Irbesartan in Bulk and Pharmaceutical Formulation T Research Article