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671.
Antimony(V) is volatilized by reaction with potassium bromide in concentrated sulfuric acid media. After volatilization, the gases can be transported to an inductively coupled plasma spectrometer for atomic emission of antimony and its analytical determination. The influent factors, concentrated sulfuric acid volume, concentration and volume of the potassium bromide aqueous solution and carrier gas flow were investigated and optimized using different alternatives. A detection limit of 48 ng ml−1 of Sb was achieved under the optimized conditions with a precision of 7.6% and the calibration graph was linear from 0.10 to 10.0 μg ml−1 for a sample injection of 130 μl.The study of interferences from common cations and anions revealed a good tolerance for most ions, although there was a significant improvement in Sb(V) volatility when As(III) was present. Furthermore, the As(III) sensitization was only produced with Sb(V) species, while the volatility of the Sb(III) bromide species was unaltered.The method was applied to the determination of Sb in real river waters. The results were checked using alternative atomic spectroscopy methods. 相似文献
672.
Naohisa Yanagihara S. Eduardo del Castillo Tetsuya Ogura 《Transition Metal Chemistry》1987,12(1):12-14
Summary Volumetric measurements of ethylene and simple EDTA titration of copper(I) and copper(II) ions confirm that [CuL]+ and [CuL2]+ are formed when an aqueous solution of copper(II) is reduced by copper metal in the presence of ethylene, (L). The formation constants,K
1=[CuL+]2[Cu2+]–1[L]–2 andK
2=[CuL
2
+
]–1[L]–1, have been estimated. The formation of [CuL]+ is accompanied by an enthalpy change, H, of –25 kJ mol–1, and a positive entropy change, S, of 13 J mol–1 K–1. 相似文献
673.
The influence of HCI concentration (6M, 8M, and 10M) and the ratio of sample protein to acid (1 or 5 mg of protein per mL of acid) on furosine formation during sample hydrolysis is studied. The conditions that maximize furosine formation are 10M HCI in the ratio of 1 mg of protein to 1 mL of acid. Purification of the hydrolysate by solid-phase extraction is also considered by examining the effect of hydrolysate volume and volume of 3M HCI used to elute the furosine. Furosine quantitation is carried out using the standard additions and external standard methods. The results indicate that there is no interference by the sample matrix and that external calibration is adequate. 相似文献
674.
A bond path linking two saturated fluorine atoms is found to be ubiquitous in crowded difluorinated aromatic compounds. The bond path is shown to persist for a range of internuclear distances (2.3-2.8 A) and a range of relative orientations of the two C-F internuclear axes. The F. . .F bonding is shown to exhibit all the hallmarks of a closed-shell weak interaction. The presence of such a bond path can impart as much as 14 kcal/mol of local stabilization to the molecule in which it exists, a stabilization that can be offset or even overwhelmed by destabilization of other regions in the molecule. Several other weak closed-shell interactions were also found and characterized including F. . .C, F. . .O, and C. . .C interactions, hydrogen bonding, dihydrogen bonding, and hydrogen-hydrogen bonding. This study represents another example of the usefulness and richness of the bond path concept and of the theory of atoms in molecules in general. 相似文献
675.
676.
, . , - . , , , . 相似文献
677.
Joachim Roll Heiko Tewes Eduardo Castillo Soto Enrique Oate Rodríguez 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(2):m43-m45
The title compound, [W(C5H5)(HOBF3)(CO)3], has a four‐legged piano‐stool geometry which is typically found for C5H5W(CO)3X complexes. The HOBF3− anion is the hydrolysis product of BF4− and is coordinated via oxygen. 相似文献
678.
Jin An Wang Gabliela González Lifang Chen Miguel A. Valenzuela Maria Moran-Pineda Armando Vázquez Salvador Castillo 《Reaction Kinetics and Catalysis Letters》2007,90(2):381-387
Ceria-zirconia nanophase with structural defects and high thermal stability was synthesized by a surfactant-templated method.
The 0.5 wt.% Rh/ceria-zirconia catalyst shows high activity for NO reduction by CO under an oxygen-rich condition, and the
selectivity to 100% N2 below 200°C was achieved. 相似文献
679.
We study the global and local approaches to the problem of extension of operators into Lindenstrauss spaces.
The research of the first author has been supported in part by DGICYT project MTM2004-02635. 相似文献
680.
Closed formulas in local sensitivity analysis for some classes of linear and non-linear problems 总被引:1,自引:0,他引:1
This paper presents an integrated approach to sensitivity analysis in some linear and non-linear programming problems. Closed
formulas for the sensitivities of the objective function and primal and dual variables with respect to all parameters for
some classes of problems are obtained. As particular cases, the sensitivities with respect to all data values, i.e., cost
coefficients, constraints coefficients and right hand side terms of the constraints are provided for these classes of problems
as closed formulas. The method is illustrated by its application to several examples.
相似文献