1.Introduction: Valsartan is a potent, orally active nonpeptide tetrazole derivative which causes reduction in blood pressure and anis used in treatment of hypertension. Valsartan is 3- methyll-2-[pentanoyl-[ [4-[2-(2H-tetrazoyl-5yl) phenyl] phenyl] methyl] amino] butanoic acid, with empirical formula C24H29N5O3. Valsartan is not extensively metabolized and is mainly excreted by non-renal routes [1]. Several methods like thin-layer chromatographydensitometric method [2], liquid chromatographic system with fluorescence detection [3] and capillary electrophoresis [4], have been reported for determination of valsartan in biological systems. But these methods are expensive and not economically. In this study, we report a novel spectrofluorimetric method for the determination of Valsartan by magnetic nanoparticle. 2.Methods/ Experimental: Magnetic nanoparticles (MNSs) were synthesized by the solvothermal reduction method with minor modifications [5]. Then, these MNSs were used to prepared silica coated magnetite nanospheres (SCMNSs). Finally the surface of SCMNSs was modified by 3- aminopropyltriethoxysilane as amine functional groups. The resultant product (NH2- SCMNSs) was collected. 2.1 general procedure The interaction of valsartan and NH2-SCMNSs was followed spectroflurimetrically by monitoring the change in the fluorescence intensity of valsartan after adsorption on the surface of NH2-SCMNSs and desorption of the nanoparticles surface in optimum conditions. 3.Results and Discussion: Prepared NH2-SCMNSs were characterized by TEM, XRD and FT-IR measurement. Solution pH important parameter that affects adsorption process of valsartan. The solution pH would affect both aqueous chemistry and surface binding-sites of the adsorbent. The effects of pH were tested in the range 2.0-10.0 using Britton-Robinson buffer with ultrasonication time of 15 min and nanospheres dosage of 3.50 mg . in this condition we reached maximum signal at pH 4.0. In order to optimize the use of NH
