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Samaneh Salari Abdulrahman Bahrami Farhad Ghamari Farshid Ghorbani Shahna 《Chemical Papers》2018,72(8):1945-1952
The present study developed a liquid-phase microextraction based on hollow fiber coupled with graphite furnace atomic absorption spectrometry for the effective extraction and quantitation of lead from urine and blood samples. A multivariate design was used for the optimization of the experimental conditions to ensure high extraction efficiency. Six factors (solvent type, chelating agent, time extraction, temperature, donor phase pH, and acceptor phase pH) were obtained by screening eleven factors of the Plackett–Burman design; these were optimized using the central composite design of response surface methodology. The optimum conditions of donor phase pH, acceptor phase pH, temperature, and extraction time were 5, 9.5, 40 °C, and 120 min, respectively. In addition, oleic acid containing dicyclohexyl-18-krone-6 was used for the membrane phase. Under optimal conditions, the enrichment factor, limit of detection, and limit of quantification were obtained in the ranges of 21.3–18.7, 0.001–0.002 ng mL?1, and 0.008–0.01 ng mL?1, respectively, in urine and blood samples. The linearity of the calibration curve was established for the concentration of Pb in the range of 1–50 ng mL?1 (r2?=?0.9983). Finally, the performance of the developed method was evaluated for the determination of lead in urine and blood samples, and satisfactory results were obtained (RSDs <?10% with recovery >?95). 相似文献
23.
Parisa Pazhooh Roushan Khoshnavazi Leila Bahrami Elham Naseri 《Journal of the Iranian Chemical Society》2018,15(8):1775-1783
New nanocomposites containing sandwich-type polyoxometalate of [(PW9O34)2(HOSnIVOH)3]12? (P2W18Sn3) loaded onto Ln-doped TiO2 (Nd, Sm, Dy, Tb) nanoparticles were synthesized and their catalytic activities were assessed. The Ln–TiO2 nanoparticles and Ln–TiO2/P2W18Sn3 nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, field emission scanning electron microscope, energy dispersive analysis of X-rays spectra and diffuse reflectance spectra. The photocatalytic efficiency of the Ln–TiO2 and Ln–TiO2/P2W18Sn3 were examined in the photodegradation of methyl orange and methylene blue solutions. It was revealed through different characterization techniques that the P2W18Sn3 was successfully loaded on the lanthanide-doped anatase phase TiO2 nanoparticles and the particles diameter were relatively 20–30 nanometers. It was revealed that doping by the lanthanide ions followed by loading of polyoxometalates improves the photocatalytic performance of TiO2 effectively. The effects of operational parameters and the kinetics of photocatalytic degradation under UV light were discussed. The prepared nanocomposites were stable and could be easily separated from the reaction system. 相似文献
24.
The kinetics of the permanganic oxidation process of glycine, L-alanine and L-leucine in strong acid media were investigated using a spectrophotometric technique. Conclusive evidence has proven that the autocatalytic activity of Mn(II) in these reactions in strong acidic media is analogous to that of weak acid media, but in the former, Mn(II) ions should acquire a critical concentration for them to show autocatalytic characteristics. This critical concentration depends on the nature of the amino acid used. Considering the delayed autocatalytic behavior of Mn(II) ions, we herein present the rate equations and mechanisms satisfying observations for both catalytic and noncatalytic routes. The correspondence of the pseudo-order rate constants of the catalytic and noncatalytic pathways to Eyring law verify both the critical concentration as well as the delayed autocatalytic behavior concepts. In general, the onset of delayed behavior can be attributed to the concentration ratio of Mn(II) to amino acid which can be of a certain value for any particular amino acid. 相似文献
25.
A new, convenient method for the syntheses of 2-substituted benzimidazole and benzothizole is described. Short reaction times, large-scale synthesis, easy and quick isolation of the products, excellent chemoselectivity, and excellent yields are the main advantages of this procedure. 相似文献
26.
Highly hydrolytic and thermally stable sandwich-type polyoxometallates of [(A-β-SiW9O34)2(MOH2)3CO3]13− (M = Y3+ and Yb3+) have been synthesized at room temperature by stoichiometric reactions of the trilacunary ligand with M3+ in 0.1 M carbonate solution. The new complexes were isolated as sodium and mixed sodium/potassium salts and were characterized by elemental analysis, IR, 13C and 29Si NMR, UV–Vis spectroscopy, TGA, DSC and single crystal structure analysis. The crystal structure of the complexes consist of two lacunary Keggin moieties which are linked by a (H2OMO)3C belt into an assembly of virtual C2 symmetry. Each M3+ ion adopts a mono-capped trigonal-prismatic coordination. The C2 axis of the complexes and the local 3-fold axis of the MO6 group lies in the (H2OMO)3C belt plane. The trigonal prismatic geometry is achieved by the two terminal oxygen atoms of an edge shared pair of WO6 octahedra from each moiety and two oxygen from the belt, and the cap by one external water ligand. The hydrolytic and thermal stabilities of the complexes and the reasons that prove the retention of the isomeric form of the trilacunary ligand upon complexation are discussed. 相似文献
27.
High sensitive determination of trace amount of cobalt by catalytic adsorptive stripping voltammetry
S. Bahrami S. Abbasi Y. A. Ghorbani A. A. Miran-Beigi 《Russian Journal of Electrochemistry》2009,45(2):208-214
A very sensitive and selective catalytic adsorptive cathodic stripping procedure for trace measurements of cobalt is presented.
The method is based on adsorptive accumulation of cobalt-CCA (calcon carboxylic acid) complex onto a hanging mercury drop
electrode followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. The reduction
current is enhanced catalytically by nitrite. The effect of various parameters such as pH, concentration of CCA, concentration
of nitrite, accumulation potential and accumulation time on the selectivity and sensitivity were studied. The optimum condition
for the analysis of cobalt, include pH 5.2 (Acetate buffer), 2.1 μM clacon carboxylic acid, 0.032 M sodium nitrite and an
accumulation potential of 0.05 V (versus Ag/AgCl). Under these optimum conditions and for an accumulation time of 60 s, the
measured peak current at −0.480 V is proportional to the concentration of cobalt over the entire concentration range tested
0.003–2.0 ng ml−1 with a detection limit of 1 pg ml−1 for an accumulation time of 60 s and 2.0–10.0 ng ml−1 for an accumulation time of 40 s. The relative standard deviations for ten replicate measurement of 0.5 ng ml−1 of cobalt were 3.1%. The main advantage of this new system is the microtrace Co(II) determination by ASV. The method was
applied to determination of cobalt in a water sample and some analytical grade salts with satisfactory results.
Published in Elektrokhimiya in Russian, 2009, Vol. 45, No. 2, pp. 221–228.
The article is published in the original. 相似文献
28.
Igor V. Mastikhin Aidin Arbabi Benedict Newling Abdelhaq Hamza Alexander Adair 《Experiments in fluids》2012,52(1):95-104
In acoustic cavitation, the relationship between the bubble dynamics on the microscale and the flow properties on the macroscale
is critical in determining sonochemical reaction kinetics. A new technique was developed to measure the void fraction and
estimate water mobility in the vicinity of cavitating bubbles using phase-encoded magnetic resonance imaging with short characteristic
measurement timescales (0.1–1 ms). The exponential behavior of the NMR signal decay indicated the fast diffusion regime, with
the relationship between local mechanical dispersion D
mix and the average bubble radius R,
Dmix >> \frac2R210-4s, D_{\rm mix}\gg \frac{2R^2}{10^{-4}\hbox{s}}, resulting in dispersion of orders of magnitude greater than diffusion in quiescent water. For two different samples (water
and a surfactant solution), the independent measurements of three-dimensional void fraction and velocity fields permitted
the calculation of compressibility, divergence and vorticity of the cavitating medium. The measured dynamics of the dissolved
gas, compared with that of the surrounding liquid, reflected the difference in the bubble coalescence and lifetimes and correlated
with the macroscopic flow parameters. 相似文献
29.
Farrokhi Chaykandi Zahra Bahrami Ali Mohammadnejad Shahram 《Optical and Quantum Electronics》2018,50(7):1-20
Optical and Quantum Electronics - A theoretical analysis of the modulational instability (MI) in a nonlinear oppositely directional coupler with one channel fabricated from nonlinear medium having... 相似文献
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In this study, the effect of Mg substitution on structural, magnetic and electrical properties of La0.75Sr0.25Mn1?xMgxO3 and La0.75Sr0.25?xMgxMnO3 (nominal compositions) samples are investigated by XRD, Ac susceptibility and electrical resistivity measurements. It is found that Mg does not replace La in the perovskite lattice. Also the results show that by increasing Mg doping levels, the paramagnetic–ferromagnetic and metal–insulator transition temperatures decrease. The reason for decreasing transition temperatures with increasing Mg concentration is, that the long-range FM order has been destroyed by the Mg, which is randomly occupying Mn site. This leads to the suppression of double-exchange interaction in the Mn3+–O–Mn4+ networks. Also the reentrant spin glass (RSG) state accompanied by FM transition, exists in high doped samples. The RSG state could be understood on the basis of double exchange ferromagnetic interaction in Mn3+–O–Mn4+ and super-exchange antiferromagnetic interaction in the Mn4+–O–Mn4+ networks. 相似文献