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941.
Raúl A. Gil José A. Salonia José A. Gásquez Alejandro C. Olivieri Roberto Olsina Luis D. Martinez 《Microchemical Journal》2010,95(2):306-310
A novel method for the determination of Pb by on-line cloud point extraction coupled to inductively coupled plasma optical emission spectrometry with ultrasonic nebulization (USN–ICP OES) is presented. The cloud point system was formed in the presence of non-ionic micelles of polyethyleneglycolmono-p-nonylphenylether (PONPE 7.5) and was retained in a minicolumn filled with particles of PTFE. Since the micelles of PONPE were able to extract Pb from the solutions, the use of a complexing reagent was not necessary. Afterwards, the surfactant-rich phase containing the analyte was removed from the minicolumn with nitric acid and introduced into the ultrasonic nebulizer. A total enhancement factor of 150 was obtained for a preconcentration time of 3.3 min, with respect to the direct determination of Pb by conventional ICP OES. The values of the detection (3σ) and quantification (10σ) limits for the preconcentration of 10 mL of sample solution were 0.09 µg L− 1 and 0.2 µg L− 1 respectively. The precision, expressed as the relative standard deviation (RSD), for 10 replicate determinations at 5.0 µg L− 1 Pb level was 6.0%. Verification of the accuracy was carried out by analysis of two certified reference materials (NIST SRM 1640e and VKI QC Metal LL1). The method was successfully applied to the determination of Pb in drinking water samples. 相似文献
942.
Viktor Jobbágy Norbert Kávási János Somlai Borbála Máté Tibor Kovács 《Microchemical Journal》2010,94(2):159-165
Hungary is rich in spring waters. A survey studying the naturally occurring alpha emitter radionuclides in 30 frequently visited and regularly consumed spring waters was conducted out in the Balaton Upland region of Hungary.226Ra, 224Ra, 234U, 238U and 210Po activity concentrations were determined by using alpha spectrometry after separation from matrix elements. Average concentration (mBq L− 1) of 226Ra, 224Ra, 234U, 238U and 210Po in the spring waters is varied from 2.1 to 601, from < 1.1 to 65.4, from 3.9 to 741.9, from < 0.44 to 274.3 and from 2 to 15.2 respectively. In most cases radioactive disequilibrium was observed between uranium and radium isotopes. The doses for the analyzed samples of spring water are in the range 3.59–166.73 μSv y− 1 with an average 18.2 μSv y− 1 .This is well below the 100 μSv y− 1 reference level of the committed effective dose recommended by WHO. Only one water sample had a dose higher than 100 μSv y− 1, mainly due to the contribution from radium (226Ra, 224Ra) and 210Po isotopes. This study provides important information for consumers and authorities about their internal radiological exposure risk from spring water intake. 相似文献
943.
944.
945.
The interactions of water molecule with platinum dioxygen complex and dioxide molecule are investigated by means of matrix isolation infrared spectroscopy and density functional calculations. The platinum atoms reacted with dioxygen to form the previously reported Pt(O2) complex. The Pt(O2) complex reacted with water molecule to give the Pt(O2)–H2O complex, which was characterized to involve hydrogen bonding between one O atom of Pt(O2) and one H atom of H2O (structure A ). Upon visible light irradiation, the hydrogen bonded Pt(O2)???HOH complex rearranged to another Pt(O2)–H2O isomer (structure B ), which involves (O2)Pt???OH2 interaction. The Pt(O2)–H2O complex in structure B can be isomerized to the weakly bound platinum dioxide‐water complex (structure C ) under UV irradiation. 相似文献
946.
FANG YaHui & LIU ZhiPan Shanghai Key Laboratory of Molecular Catalysis Innovative Materials 《中国科学:化学》2010,(3)
Theoretical simulations on complex electrochemical processes have been developed on the basis of the understanding in electrochemistry,which has benefited from quantum mechanics calculations.This article reviews the recent progress on the theory and applications in electrocatalysis.Two representative reactions,namely water electrolysis and oxygen reduction,are selected to illustrate how the theoretical methods are applied to electrocatalytic reactions.The microscopic nature of these electrochemical reaction... 相似文献
947.
We have fabricated novel nanofibrous fluorinated polyimide membranes on a specially designed collector, which is composed of conductive aluminum plates and glass insulator materials and can be removed from the apparatus, using an electrospinning method. We describe the structure and water flux properties of the nanofibrous fluorinated polyimide membranes. The electrospun nanofibers were deposited across the plates and uniaxially aligned to the collector. In addition, the multi‐layer stacked nanofibrous membranes, consisting of three‐dimensionally ordered nanopores, were produced. The pure water fluxes for the stacked membranes were measured, using a stirred dead‐end filtration cell, and were linearly decreased with an increasing deposition time, indicating that the nanopores formed in the nanofibrous membrane were further narrowed due to the regularly accumulated nanofibers. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
948.
在550℃~650℃,24 MPa~30 MPa,反应停留16 s~46 s的条件下,对初始浓度0.05 mol/L~0.70 mol/L的甲酸溶液在超临界水中的降解过程进行实验研究。结果表明,甲酸降解的气体产物为H2、CO2和CO,其中H2、CO2为主要产物。高温有利于甲酸降解和H2生成。温度较高(600℃)时,压力变化对甲酸降解无明显影响。在一定范围内延长反应时间可提高气体产物中H2的体积分数和碳气化率。甲酸初始浓度对甲酸降解机理有重要影响,浓度较低(0.1 mol/L)时,甲酸降解主要包含脱羧反应和脱羰反应两条反应路径,其中脱羧反应为主反应路径;浓度较高时则有许多副反应发生。碱性添加剂不利于甲酸降解生成H2。 相似文献
949.
950.
We describe an algorithm for computing nonbonded interactions with cutoffs on a graphics processing unit. We have incorporated it into OpenMM, a library for performing molecular simulations on high‐performance computer architectures. We benchmark it on a variety of systems including boxes of water molecules, proteins in explicit solvent, a lipid bilayer, and proteins with implicit solvent. The results demonstrate that its performance scales linearly with the number of atoms over a wide range of system sizes, while being significantly faster than other published algorithms. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献