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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.
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
3.
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
4.
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
5.
Ludvík Beneš Klára Melánová Vítězslav Zima Jaroslava Kalousová Jiří Votinský 《Journal of inclusion phenomena and macrocyclic chemistry》1998,31(3):275-286
Recent knowledge of the kinetics and intercalation mechanisms are summarized and accompanied by examples of intercalation reactions of water and ethanol into anhydrous vanadyl phosphate and redox intercalation of alkali metal cations into vanadyl phosphate dihydrate. Three possible mechanisms of intercalation are presented which are based on: (i) a concept of exfoliation of layers; (ii) the formation of stages and randomly stacked layers; (iii) co-existence of intercalated and non-intercalated parts of crystals of the host separated by an advancing phase boundary. The corresponding kinetic curves are ascribed to mechanisms (ii) and (iii). 相似文献
6.
Ewelina Minta 《Tetrahedron letters》2005,46(11):1795-1797
Alkali metal trimethylsilanolates, TMSO−, M+, has been used for efficient conversion of methyl esters into their corresponding anhydrous acid salts under mild non-aqueous conditions. This strategy has been applied to SPPS for the preparation of neurotoxin cyclic analogues and in (S)-5-hydroxynorvaline synthesis. 相似文献
7.
Ludvík Beneš Vítězslav Zima 《Journal of inclusion phenomena and macrocyclic chemistry》1994,20(4):381-391
The course of intercalation of water into 1-VOPO4 has been studied by thermomechanical analysis and X-ray diffraction. Neither formation of vanadyl phosphate monohydrate nor staging were observed during the intercalation. The broadening and the shift of the positions of the lines in the diffractograms have been explained by the random stacking of intercalated and nonintercalated layers in the sample. 相似文献
8.
Valdas Laurinavicius Julija Razumiene Bogumila Kurtinaitiene Ingrida Lapenaite Irina Bachmatova Liucija Marcinkeviciene Rolandas Meskys Arunas Ramanavicius 《Bioelectrochemistry (Amsterdam, Netherlands)》2002,55(1-2):29-32
This paper focuses on the use of PQQ-dependent enzymes (PQQ enzymes) in amperometrical biosensors and gives emphasis on their innovative designs and applications. The study covers some aspects in the evolution of biosensors based on PQQ enzymes. Main attention is focused on the electrochemical properties of PQQ enzymes as very promising materials for the formation of electrochemical biosensors. Immobilization approaches and redox mediators recently used in PQQ enzymes based biosensors are reviewed. The acceptance of polypyrrole as a very promising immobilization matrix for some PQQ enzymes is discussed. 相似文献
9.
Ewelina Nawrot 《Journal of fluorine chemistry》2006,127(7):943-947
N-Aryl substituted amides react with chlorodifluoromethane in the presence of concentrated aqueous sodium hydroxide and benzyltriethylammonium chloride (TEBAC) as a catalyst in benzene (phase-transfer catalysis, PTC), affording mixtures of N- and O-difluoromethyl substituted derivatives. Amide anions are involved in this process. The reaction carried out with oximes gives O-difluoromethyl oxime ethers. 相似文献
10.
The polarographic behaviour of 2-nitronaphthalene was investigated by DC tast polarography (DCTP) and differential pulse polarography (DPP), both at a dropping mercury electrode, and differential pulse voltammetry and adsorptive stripping voltammetry, both at a hanging mercury drop electrode. Optimum conditions have been found for the determination of 2-nitronaphthalene by the given methods in the concentration ranges of 2×10–6–1×10–4, 2×10–7–1×10–4, 1×10–8–1×10–4 and 2×10–9–1×10–8 M, respectively. Practical applicability of these techniques was demonstrated by the determination of 2-nitronaphthalene in drinking and river water after its preliminary separation and preconcentration using liquid–liquid and solid-phase extraction with limits of determination of 3×10–10 M (drinking water) and 3×10–9 M (river water). 相似文献