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1.
We have studied antimony and selenium atomization processes including a chemical matrix modifier (palladium-containing activated
carbon) during their determination by electrothermal atomic absorption spectrometry. We have developed and fine-tuned an experimental
setup for determining the kinetic characteristics (activation energy and frequency factor) for element atomization processes
from measurements in the initial section of the analytical signal. We provide a rationale for the most likely mechanism for
the interactions that occur. The results of the kinetic studies of the atomization processes showed that the modifier we developed
was highly effective, as a result of formation of a thermally stable condensed system C-Pd-A (where A is the analyte).
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 530–534, July–August, 2006. 相似文献
2.
3.
Boris V. L'vov 《Mikrochimica acta》1991,104(1-6):299-308
A basically new mechanism of the thermal decomposition of solids is proposed to explain the mass spectral observations of gaseous molecules of CoO, CuO, Cu2O, NiO, PbO and Mg(OH)2 during the low-temperature decomposition of the anhydrous and hydrated nitrates of these metals. The mechanism consists of two stages: congruent gasification of all reaction products irrespective of their saturated vapor pressure and subsequent condensation of the low-volatility species (oxides and hydroxides). The partial pressures of these species at the appearance temperatures calculated from this theory for the first stage of the process (1–50 mPa) are in agreement with the detection limits of the quadrupole mass spectrometers used in these experiments. The proposed mechanism is supported by other available data obtained by thermal analysis. 相似文献
4.
5.
A simple procedure for the determination of manganese in different sections of human brain samples by graphite furnace atomic absorption spectrometry has been developed. Brain sections included cerebellum, hypothalamus, frontal cortex, vermix and encephalic trunk. Two sample preparation procedures were evaluated, namely, slurry sampling and microwave-assisted acid digestion. Brain slurries (2% w/v) could be prepared in distilled, de-ionized water, with good stability for up to 30 min. Brain samples were also digested in a domestic microwave oven using 5 ml of concentrated HNO3. A mixed palladium+magnesium nitrate chemical modifier was used for thermal stabilization of the analyte in the electrothermal atomizer up to pyrolysis temperatures of 1300 °C, irrespective of the matrix. Quantitation of manganese was conducted in both cases by means of aqueous standards calibration. The detection limits were 0.3 and 0.4 ng ml−1 for the slurry and the digested samples, respectively. The accuracy of the procedure was checked by comparing the results obtained in the analysis of slurries and digested brain samples, and by analysis of the NIST Bovine Liver standard reference material (SRM 1577a). The ease of slurry preparation, together with the conventional set of analytical and instrumental conditions selected for the determination of manganese make such methodology suitable for routine clinical applications. 相似文献
6.
1 INTRODUCTION The bimetallic nanoclusters are of standing inte- rest since they can exhibit catalytic, electronic and optical properties distinct from those of corre- sponding pure nanoclusters[1~4]. Palladium and pla- tinum, well known for their catalytic properties, are often used as the catalyst in different fuel cells[5~8]. Several experimental results illustrate that for the oxygen reduction reaction (ORR), which is one of the primary reactions taking place in many fuel cells and… 相似文献
7.
On the Thermodynamics of Vaporization and the Enthalpies of Formation of CaSe, SrSe and BaSe The congruent vaporization of the solid compounds CaSe, SrSe and BaSe of stoichiometric composition was studied over the temperature ranges 1832?2138 K, 1862?2122 K and 1860?2158 K, respectively, by the Knudsen effusion weight-loss method. Using enthalpy and entropy data from the literature for gaseous M, MSe, Se2 and Se (M = Ca, Sr, Ba) and estimated data for the standard entropies and enthalpy functions of solid MSe, it can be shown that within the given temperature ranges CaSe and SrSe vaporize predominatly to the atomic species, while in case of BaSe the mode of vaporization to the atoms and to the molecular species BaSe are of about equal importance. The Se2-content of the gas phase is very small in all cases. The following second and third law enthalpies and entropies (indices II and III respectively) were derived for the vaporization to the gaseous elements: see “Inhaltsübersicht”. The following standard enthalpies of formation of MSe(s) were derived from the third law enthalpies (in kJ · mol?1): CaSe: ?445 ± 44; SrSe: ?451 ± 42; BaSe: ?467 ± 44. 相似文献
8.
Using our technique of combustion of small amount of a substance, we determined by calorimetry the standard molar enthalpy of formation in the condensed state and atT=298.15 K of the three isomers of bromo and iodobenzoic acids. Associating to these values their standard molar enthalpies of sublimation previously measured, it was possible to determine their standard molar enthalpies of formation in the gaseous state and atT=298.15 K. The experimental values of the thermodynamic properties f
H
m
o
(cr, 298.15 K), f
H
m
o
(cr, 298.15 K), sub
H
m
o
(298.15 K), and f
H
m
o
(g, 298.15 K) are given for the two series. From the experimental value of the standard molar enthalpy of atomization, it was possible to determine an enthalpy value for the Cb-Br and Cb-I bonds. The experimental and theoretical values of the resonance energy of bromo and iodobenzoic acids are compatible. The relative stability of some monosubstituted derivatives of benzoic acid studied in our laboratory is also discussed.Part I is concerned with Ref. 22 (for bromobenzoic acids) and with Ref. 23 (for iodobenzoic acids). 相似文献
9.
本文应用x-射线衍射(XRD)、X-射线光电子能谱(XPS)、俄歇电子能谱(AES)、扫描电子显微技术(SEM)研究了钼酸铵在石墨炉内石墨探针表面上的原子化机理。实验结果表明,在温度<1350K时,钼酸铵经历MoO_3和Mo_4O_(11)中间产物转变为MoO_2(s)。在更高温度下,MoO_2(s)首先还原为Mo_2C,而后进一步转变为MoC(s)。MoC再分解为Mo(s)。钼的原子化起源于Mo的升华。 相似文献
10.
A general procedure has been developed for the simulation of charged liquid and electrostatically atomized sprays. The procedure follows a Lagrangian approach for simulation of spray droplets and a Eulerian approach for gas‐phase variables, including the electric field generated by the charge presence on droplets. Validation of the procedure was examined through simulations of previously published charged spray experiments. Results showed that for the specification of initial droplet charge, modelling the droplet charge–diameter relationship through a scaling law is as reliable a method as using a directly obtained charge–diameter relationship from experimental measurements. The normalized root‐mean‐square errors for sprays using the two methods were shown to be within 12% of one another, for the prediction of spatially averaged profiles of mean droplet diameters, mean axial velocities and mean radial droplet velocities. Results showed that the general spatial characteristics and dynamics of a charged liquid spray can successfully be reproduced, including the axial and radial dispersal pattern of droplets and the distribution of mean droplet diameters throughout the spray plume. For all sprays with droplet charges defined through a scaling law relationship, the normalized root‐mean‐square errors range from 9.0% to 31.6% for mean droplet diameters, 10.4% to 67.9% for mean axial droplet velocities and 16.8% to 38.6% for mean radial droplet velocities. Lastly, we present a brief set of general recommendations for simulating electrostatically atomized dielectric liquid sprays.Copyright © 2013 John Wiley & Sons, Ltd. 相似文献