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1.
On‐line coupling of LC and ICP‐MS has been used for fractionation and detection of species of Cu, Fe, I, Se and Zn in human serum. It has been shown that anion exchange chromatography provided better separation capability (both intra‐ and inter‐element) than size‐exclusion chromatography. The mobile phases for ion exchange chromatography consisted of Tris–HNO3 buffer and ammonium salt (nitrate, acetate or formate). Formate was found to be the best mobile phase counter ion, enabling good chromatographic separation, and is acceptable for mass spectrometry too. The quantitative evaluation of element concentrations adhering to individual fractions was performed by the peak area normalization method. The repeatability of results ranged from 3 to 15% (depending on the element concentration level) and represented the main part of the result uncertainty. The accuracy of Cu and Zn fraction determinations was confirmed by comparison with the isotope dilution technique. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
2.
The presented work offers new algorithms for phase evaluation in interferometric measurements. Several phase-shifting algorithms with an arbitrary but constant phase-shift between captured intensity frames are proposed. These phase calculation algorithms need to measure five frames of the intensity of the interference field. The algorithms are similarly derived as so called Carré algorithm. The phase evaluation process then does not depend on the linear phase shift errors. Furthermore, the detailed analysis of the algorithms with respect to most important factors, which affect interferometric measurements, is carried out. It is also studied the dependency of the evaluation algorithms on the phase shift values, and the proposed phase calculation algorithms are compared with respect to the resulting phase errors. The influence of most important factors in the measurement and evaluation process was simulated as systematic and random errors using a proposed mathematical model. 相似文献
3.
4.
We study the existence of positive solutions to the operator equation Lx = Nx, where L is a linear Fredholm mapping of index zero and N is a nonlinear operator. Using the properties of cones in Banach spaces and Leray-Schauder degree for completely continuous
operators, k-set contractions and condensing mappings, we obtain some refinements of the results established in [3] and [14].
Received: 9 July 2005; revised: 12 January 2006 相似文献
5.
Klára Melánová Ludvík Bene? Vítzslav Zima Jan Svoboda 《Journal of inclusion phenomena and macrocyclic chemistry》2005,51(1):97-101
The intercalates of Naphthol Yellow S, Tropaeolin 000, and Tropaeolin 00 were prepared by heating [Zn0.67Al0.33(OH)2](CO3)0.165 · 0.5H2O with acidic forms of the dye solutions in an open reaction vessel. The intercalates were characterized by chemical and thermal analysis, X-ray powder diffraction and UV–VIS spectroscopy. A possible arrangement of the dye molecules in the intercalates was suggested on the basis of their chemical compositions and interlayer distances, by taking into account van der Waals dimensions of the guest molecules and by assuming that the structure of the host layers is not changed during the intercalation process. 相似文献
6.
Uranium is determined via its 239U nuclide (74.0 keV, t = 23.5 min) in natural waters down to 0.03 ng U ml-1 after preconcentration with activated carbon and oxine; 30-min irradiation and counting times are used. No preconcentration is required for samples containing more than 4 ng U ml-1 with 10-min irradiation and counting times. Uranium in urine can be determined under a boron shield at the 5 ng ml-1 level after 30-min irradiation and counting. 相似文献
7.
Christoph Luef Aloke Paul Jiri Vizdal Ales Kroupa Alexander Kodentsov Herbert Ipser 《Monatshefte für Chemie / Chemical Monthly》2006,137(4):381-395
Summary. The partial and integral enthalpies of mixing of liquid Bi–Sn–Zn alloys were determined at 500°C by a drop calorimetric technique
using a Calvet-type microcalorimeter. The ternary interaction parameters in the Bi–Sn–Zn system were fitted using the Redlich-Kister-Muggianu model for substitutional solutions, and isoenthalpy curves of the integral molar enthalpy of mixing at 500°C were constructed.
Furthermore, a DSC technique was used to determine the liquidus temperatures in three sections (3, 5, and 7 at.% Zn) as well
as the invariant reaction temperature of the ternary eutectic L ⇄ (Bi) + (Sn) + (Zn). The ternary eutectic reaction was found
at 135°C. 相似文献
8.
Klára Melánová Ludvík Beneš Vítězslav Zima Jan Svoboda Miroslava Trchová Jiří Dybal 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(1-2):95-101
Intercalation compounds of α-Zr(HPO4)2 · H2O with 1,2-alkanediols (from C3 to C16) have been prepared by replacing 1-propanol in α-Zr(HPO4)2 · 2C3H7OH with the desired 1,2-alkanediols by a treatment in a microwave field. It was found that the intercalates contain 1.5 molecules
of diol per formula unit. The diol molecules are placed between the host layers in a bimolecular way with their aliphatic
chains tilted at an angle of 51°. The diol molecules are anchored in the interlayer space by H-bonds. A mixed intercalate,
containing 1,2-butanediol and 1,2-decanediol in a roughly equimolar ratio, is formed when the α-Zr(HPO4)2 · 2C3H7OH intercalate, suspended in a mixture of 1,2-butanediol and 1,2-decanediol, is exposed to microwave radiation. No new phase
containing both types of the guest molecules was observed when the 1-propanol intercalate, suspended in a mixture of 1-propanol
and 1,2-octanediol, is exposed to microwave radiation. 相似文献
9.
Ab initio investigations at the RHF and CI levels have been carried out on a section of the potential energy surface of the Rydberg 3s3A″2 state of NH3 leading to dissociation into NH2(2B1) and H(2S). It was found that the barrier towards dissociation is due to a Rydberg-valence transformation. The barrier height calculated with the CI wavefunction is significantly smaller than at the RHF level The results may explain the difficulties associated with experimental observation of the 3s3A″2 state. 相似文献
10.
Francine Vinette Jiri Cizek Edward R. Vrscay 《International journal of quantum chemistry》1987,32(6):663-667
The upper and lower bounds of a harmonic oscillator with an octic perturbation are studied with the use of renormalized inner projection. It is shown that this relatively simple technique works even in the infinite coupling constant limit. Symbolic computation is very convenient and useful in these types of problems, where only a finite number of operations are required. 相似文献