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    Electrochemical Studies of Olmesartan Medoxomil and its Detection in Pharmaceutical Dosage Forms and Biological Fluids by Cathodic Adsorptive Stripping Voltammetric Method
    (SOC BRASILEIRA QUIMICA, 2014) Öztürk, Funda; Küçükkolbaşı, Semahat; Kaçar, Ceren; Kılıç, Esma
    The electrochemical properties of olmesartan (OLME) were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) at hanging mercury drop electrode (HMDE). All studies were based on the irreversible and adsorption-controlled electrochemical reduction signal of OLME at about -1.2 and -1.5 V vs. Ag/AgCl at pH 5.0 in Britton-Robinson (BR) buffer. This adsorptive character of the molecule was used to develop a novel, fully validated, rapid, selective and simple differential pulse cathodic adsorptive stripping voltammeric (DPCAdSV) method for the direct determination of OLME in pharmaceutical dosage form and human urine without time-consuming steps prior to drug assay. Peak current of electrochemical reduction of OLME was found to vary linearly with the concentration in the range from 4.7 x 10(-8) mol L-1 (0.0262 mu g mL(-1)) to 8.3 x 10(-6) mol L-1 (4.636 mu g mL(-1)). In this method, limit of quantification (LOQ) was found to be 5.1 x 10(-7) mol L-1 (0.284 mu g mL(-1)). The method was applied to determine the content of OLME in commercial pharmaceutical preparation and spiked human urine. It was found to be highly accurate and precise, having a relative standard deviation of less than 10% for all applications.
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    Magnetite Nanoparticles and Prussian Blue Modified Amperometric Biosensor for Lactic Acid Determination
    (Selçuk Üniversitesi Fen Fakültesi, 2016) Kaçar, Ceren; Öztürk, Funda; Erden, Pınar Esra; Kılıç, Esma
    Carbon paste electrode modified with lactate oxidase (LOx) enzyme, Fe3O4 nanoparticles and Prussian blue (PB) was investigated as amperometric biosensor for lactic acid. LOx was immobilized by cross-linking with glutaraldehyde (GA) and bovine serum albumin (BSA) into carbon paste matrix. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to investigate the electron transfer properties of bare and modified carbon paste electrodes. The parameters affecting the analytical performance of the enzyme electrode have been investigated in detail and optimized. The optimum response to lactic acid was obtained in 0.05 M phosphate buffer at pH 5.5 when polarized at +0.10 V vs. Ag/AgCl. The biosensor provides a linear response for lactic acid in the concentration range of 7.5×10-6 ?1.3×10-4 M with a detection limit of 5.9×10-7 M and correlation coefficient of 0.998. The effects of interferents, the operational and storage stabilities of the biosensor were also evaluated. The biosensor showed 5.4% loss in its initial activity after one week when stored at +4°C.