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Norouzi Parviz Ganjali Mohammad Reza Qomi Mahnaz Nemati Kharat Ali Zamani Hassan Ali 《中国化学》2010,28(7):1133-1139
A continuous cyclic voltammetric study of letrozole at gold microelectrode was carried out. The drug in phosphate buffer (pH 2.0) is adsorbed at ?200 mV, giving rise to change in the current of well‐defined oxidation peak of gold in the flow injection system. The proposed detection method has some of advantages, the greatest of which are as follows: first, it is no more necessary to remove oxygen from the analyte solution and second, this is a very fast and appropriate technique for determination of the drug compound in a wide variety of chromatographic analysis methods. Signal‐to‐noise ratio has significantly increased by application of discrete Fast Fourier Transform (FFT) method, background subtraction and two‐dimensional integration of the electrode response over a selected potential range and time window. Also in this work some parameters such as sweep rate, eluent pH, and accumulation time and potential were optimized. The linear concentration range was of 1.0×10?7?1.0×10?10 mol/L (r=0.9975) with a limit of detection and quantitation 0.08 nmol/L and 0.15 nmol/L, respectively. The method has the requisite accuracy, sensitivity, precision and selectivity to assay letrozol in tablets. The influences of pH of eluent, accumulation potential, sweep rate, and accumulation time on the determination of the letrozol were considered. 相似文献
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Hosseini M Ganjali MR Tavakoli M Norouzi P Faridbod F Goldooz H Badiei A 《Journal of fluorescence》2011,21(4):1509-1513
A novel and simple fluorescence enhancement method for selective pyrophosphate(PPi) sensing was proposed based on a 1:1 metal
complex formation between bis(8-hydroxy quinoline-5-solphonat) chloride aluminum(III) (Al(QS)2Cl), (L) and PPi in aqueous solution. The linear response range covers a concentration range of 1.6 × 10−7 to 1.0 × 10−5 mol/L of PPi and the detection limit of 2.3 × 10−8 mol/L. The association constant of L-PPi complex was calculated 2.6 × 105 L/mol. L was found to show selectively and sensitively fluorescence enhancement toward PPi over than I3-, NO3-, CN−, CO32−, Br−, Cl−, F−, H2PO4− and SO42−, which was attributed to higher stability of inorganic complex between pyrophosphate and L. 相似文献
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Xiangbo Meng Mihnea Ionescu Mohammad Norouzi Banis Yu Zhong Hao Liu Yong Zhang Shuhui Sun Ruying Li Xueliang Sun 《Journal of nanoparticle research》2011,13(3):1207-1218
This study attempted to synthesize one-dimensional (1D) coaxial nanotubes of Fe2O3 based on carbon nanotubes (CNT@Fe2O3) via atomic layer deposition (ALD) using ferrocene and oxygen as precursors. Results disclosed that undoped CNTs were suitable
for the ALD of Fe2O3 (ALD-Fe2O3) only if they were chemically functionalized, due to their inert surface nature. It was further demonstrated that the effects
of both covalent and non-covalent methodologies were limited in functionalizing undoped CNTs, leading to random and non-uniform
deposition of Fe2O3. In sharp contrast, it was found that, as an alternative, nitrogen-doped CNTs (N-CNTs) contributed uniform and tunable ALD-Fe2O3, due to their active surface nature induced by incorporated N atoms. Consequently, various 1D heterostructural coaxial nanotubes
were obtained with well-controlled growth of Fe2O3 on N-CNTs. For a better understanding, the underlying mechanisms were explored based on different N-doping configurations.
In addition, high-resolution transmission electron microscopy and X-ray diffraction jointly demonstrated that as-deposited
Fe2O3 is single-phase crystalline α-Fe2O3 (hematite). The as-synthesized heterostructural coaxial nanotubes of CNT@Fe2O3 may find great potential applications in photocatalysis, gas-sensing, and magnetic fields. 相似文献
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In this paper, fully developed convective heat transfer of viscoelastic flow in a curved pipe under the constant heat flux at the wall is investigated analytically using a perturbation method. Here, the curvature ratio is used as the perturbation parameter and the Oldroyd-B model is applied as the constitutive equation. In the previous studies, the Dirichlet boundary condition for the temperature at the wall has been used to simplify the solution, but here exactly the non-homogenous Neumann boundary condition is considered to solve the problem. Based on this solution, the non-axisymmetric temperature distribution of Dean flow is obtained analytically and the effect of flow parameters on the flow field is investigated in detail. The current analytical results indicate that increasing the Weissenberg number, viscosity ratio, curvature ratio, and Prandtl number lead to the increase of the heat transfer in the Oldroyd-B fluid flow. 相似文献
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In this paper, instability in the creeping viscoelastic flow inside a curved rectangular duct is investigated numerically for the first time. Using the Criminale–Eriksen–Filbey (CEF) model as the constitutive equation, the governing equations are solved by a second order of finite difference method based on the artificial compressibility algorithm in a staggered mesh. The effects of normal stress differences on the flow stability are investigated. The numerical results obtained indicate that the increase of the negative second normal stress difference of viscoelastic fluid causes stability in the creeping flow in curved ducts, however, the increase of the first normal stress difference intensifies the instability. Furthermore, at the special value of Ψ2/Ψ1=?0.5, the interaction of the two normal stress differences results in a stable flow field. 相似文献
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Dispersive liquid-liquid microextraction (DLLME) combined with spectrofluorimetry was applied to the extraction, pre-concentration and analysis of thiamine (vitamin B1). The procedure is based on (a) the oxidation of thiamine with ferricyanide to form fluorescent thiochrome (TC), (b) the trapping of TC into a microextraction solvent, and (c) spectrofluorometric determination. Microextraction solvent and disperser solvent are directly injected into an aqueous solution containing TC. After centrifuging, phase separation is performed by sedimenting the fine droplets of the microextraction solvent on the bottom of a test tube. The settled phase is transferred into a fluorometer for the determination of thiamine at excitation/emission wavelengths of 375/438 nm. Under the optimized experimental conditions, the method provides a linear dynamic range of 0.2–100 ng mL?1, a detection limit of 0.06 ng mL?1, and a relative standard deviation of 3.0%. The method was successfully applied to pharmaceutical formulations and human urine. The results were validated by recovery test and by comparison with other methods, and were found to be highly satisfactory. 相似文献
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ABSTRACTIn this paper, lanthanum was used as a chemical modifier for the direct determination of erbium by high-resolution continuum source electrothermal atomic absorption spectrometry. A two-step experimental design was used for optimization, first a full factorial design was conducted for identification of significant factors, and then a central composite design was carried out for final optimization of the significant factors. The optimum parameters were obtained as follows: atomization temperature of 2500°C, pyrolysis temperature of 1600°C, and pyrolysis time of 10?s in the presence of lanthanum as a chemical modifier. Under optimum conditions, the characteristic mass, limit of detection, and limit of quantification were 29?pg, 0.71, and 2.4?µg?L?1, respectively. The precision of the method, estimated as the relative standard deviation for 10 replicate measurements of 50?µg?L?1 of erbium, was 1.8%. The optimized method was applied to determine erbium content in sediments and rock samples. The determined values of erbium in sediment certified reference materials were in satisfactory agreement with the certified values according to the t-test for a 95% confidence level. 相似文献
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We prove that θ∗ as previously defined [Int. J. Contemp. Math. Sci. 5 (2010) 721] is the smallest equivalence relation such that the quotient structure R/θ∗ is a commutative fundamental ring. We also investigate some properties with respect to the commutative fundamental relation θ∗ on a hyperring R. 相似文献