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81.
《Analytical letters》2012,45(16):1297-1309
Abstract The influence of some precipitating and complexing agents on the function of Pb(II)-sensitive electrode was studied. On the basis of the experimental findings, procedures were worked out for determining oxalate, phosphate, chromate, nitrilotriacetic acid (NTA), sodium diethyldithiocarbamate (NaDDC), and diethylenetetraamine penta-acetic acid (DTPA) with a standard Pb(II) solution as a titrant and a Pb(II), -sensitive electrode as a detector. The reverse titration of Pb(II), with any of these agents could also be done. 相似文献
82.
83.
Rahul R. Kolhapurkar Preeti K. Patil Dilip H. Dagade Kesharsingh J. Patil 《Journal of solution chemistry》2006,35(10):1357-1376
Experimental measurements of the speed of sound, density and osmotic vapour pressure are reported for binary 18-Crown-6 (18C6) + CH3OH, KBr + CH3OH and ternary KBr + 18C6 + CH3OH solutions at 298.15 K. The density and compressibility data were processed to obtain the apparent molar volume (ø V ) and apparent molar isentropic compressibility ( $\phi _{K_S } Experimental measurements of the speed of sound, density and osmotic vapour pressure are reported for binary 18-Crown-6 (18C6) + CH3OH, KBr + CH3OH and ternary KBr + 18C6 + CH3OH solutions at 298.15 K. The density and compressibility data were processed to obtain the apparent molar volume (?
V
) and apparent molar isentropic compressibility () of the solutes in methanol. Expansivity data were obtained for the 18C6 + CH3OH system from density data at different temperatures and were used for calculation of the isothermal compressibility values at 298.15 K. The isothermal compressibility and expansivity data are further used to obtain the apparent molar isothermal compressibility () and apparent molar expansivity (?
E
) of 18C6 in methanolic solutions and as well as the energy-volume coefficient parameter (∂ U/∂ V)
T
in methanol solutions. The volume and compressibility changes due to complexation of KBr with 18C6 are obtained at infinite dilution for ?
V
and ?
K
. The results are compared with the similar data obtained by us previously for aqueous and CCl4 solutions. The osmotic coefficient data were used to calculate activities and activity coefficients of each component at 298.15 K as a function of the concentration of binary and ternary methanolic solutions containing KBr and 18C6. The activity and activity coefficient data are used to evaluate the pair and triplet interaction parameters by making appropriate use of the McMillan-Meyer theory of solutions. The calculation of the thermodynamic equilibrium constant (K) is made using the pair interaction parameter, g
NE
(non-electrolyte – electrolyte pair interaction), for the complexation equilibria. The nature of interactions present in the CH3OH solutions is discussed. 相似文献
84.
Detailed information on the geochemical behavior of radioactive and toxic metal ions under environmental conditions (in geological
matrices and aquifer systems) is needed in order to assess the long-term safety of waste repositories. This includes knowledge
of the mechanisms of relevant geochemical reactions, as well as associated thermodynamic and kinetic data. Several previous
studies have shown that humic acid can play an important role in the immobilization or mobilization of metal ions due to complexation
and colloid formation. In our project we investigate the complexation behavior of (purified Aldrich) humic acid and its influence
on the migration of the lanthanides europium and gadolinium (homologs of the actinides americium and curium) in the ternary
system consisting of these heavy metals, humic acid and kaolinite (KGa-1b) under almost natural conditions. Capillary electrophoresis
(CE, Beckman Coulter P/ACE MDQ), with its excellent separation performance, was hyphenated with a homemade interface to inductively
coupled plasma mass spectrometry (ICP–MS, VG Elemental PlasmaQuad 3) giving a system that is highly sensitive to the rare-earth
element species of europium and gadolinium with humic acid. The humic acid used was also halogenated with iodine, which acted
as an ICP–MS marker. To couple CE to ICP–MS, a fused silica CE capillary was flexibly fitted into a MicroMist 50 μl nebulizer
with a Cinnabar cyclonic spray chamber in the external homemade interface. The chamber was chilled to a temperature of 4 °C
to optimize the sensitivity. 200 ppb of cesium were added to the CE separation buffer so that the capillary flow could be
observed. A make-up fluid including 4 ppb Ho as an internal standard was combined with the flow from the capillary within
the interface in order to get a fluid throughput high enough to maintain continuous nebulization. Very low detection limits
were achieved: 125 ppt for 153Eu and 250 ppt for 158Gd. Using this optimized CE–ICP–MS coupling system it was possible to quantify metal concentrations from the detection limit
up to approximately 1 ppm (the linear range). This set-up was used to separate metal/humic acid-species in a 100 mM acetic
acid/10 mM acetate buffer system. Using humic acid as the complexing ligand, uncomplexed metal ion species could be separated
from metal–humate complexes on a time-resolved scale.
相似文献
85.
Christian M. Hülsbusch Martin Feigel 《Journal of inclusion phenomena and macrocyclic chemistry》2007,59(1-2):53-63
Resorc[4]arene based peptide-cavitands with four identical chiral amino acids at their upper rim were synthesized and investigated
for the complexation of small guest molecules. Competition experiments show, that the tetra amino acid cavitands complex small
organic guests in chloroform in the order ethyl acetate <dichloromethane < acetonitrile < ethanol < acetamide < acetic acid.
The peptide-cavitands containing aspartic and glutamic acid derivatives enclose parts of their attached amino acids in the
cavity, so that these peptide-cavitands are host and guest at the same time. The starting material for the cavitands, the
resorc[4]arenetetraamine 3, is made by a new synthetic route using the Delépine-reaction. 相似文献
86.
The complexation of uranium(VI) with the amino acids l-glycine and l-cysteine has been investigated by time-resolved laser-induced fluorescence spectroscopy (TRLFS) and UV–Vis spectroscopy at a low pH range. The identified 1:1 and 1:2 uranyl-l-glycine complexes fluoresce and have similar absorbance properties. In contrast to the glycine system, uranyl forms two different non-fluorescent 1:1 complexes with l-cysteine, showing individual absorbance properties under the given experimental conditions. The corresponding complex formation constants were calculated using the spectroscopic data. 相似文献
87.
Nikolay G. Lukyanenko Tatiana I. Kirichenko Catherine Yu. Kulygina Marina S. Fonari 《Tetrahedron letters》2004,45(14):2927-2930
Two representatives of a novel class of crownophanes containing fragments of fluorenone and stilbene bridged by units of diethylene glycol and triethylene glycol, respectively, have been synthesized. The crystal structure and complexation behavior of these crownophanes were studied. They form much stronger complexes with dibenzylammonium hexafluorophosphate (logKa value in CH3CN is equal to 3.92 ± 0.06 and 4.40 ± 0.05, respectively) than benzocrown ethers. This makes them an attractive alternative for benzocrown ethers as components in supramolecular synthesis. 相似文献
88.
It has been demonstrated that calcium montanate (a mixture of aliphatic hydrocarbons, fatty acid esters of C28–C32 acids, the calcium salts of these fatty acids, and the acids themselves) can be selectively extracted with supercritical fluids. By use of carbon dioxide, carbon dioxide containing 10% methanol, and carbon dioxide containing 10% methanol and citric acid (as a further additive), the various compound classes could be isolated with high selectivity. The addition of citric acid results in the complexation of Ca2+ and the simultaneous formation of the free fatty acids, which are soluble in the extractant. 相似文献
89.
Selective determination of airborne hexavalent chromium using inductively coupled plasma mass spectrometry 总被引:1,自引:0,他引:1
A new method for determining ultra-trace levels of hexavalent chromium in ambient air has been developed. The method involves a 24-h sampling of air into potassium hydroxide solution, followed by silica gel column separation of chromium (VI), then preconcentration by complexation and solvent extraction. The chromium (VI) complex was dissolved in nitric acid. The resultant chromium ions were determined by inductively coupled plasma mass spectrometry (ICP–MS) using a dynamic reaction cell (DRC) with ammonia as the reactive gas to reduce polyatomic interferences. The interconversion of chromium in potassium hydroxide solution and air sample matrix were investigated under ambient conditions. It was found that there was no conversion of chromium (VI) into chromium (III) species. However, it was observed that some chromium (III) species were converted into chromium (VI) species. For a KOH solution containing 100 μg l−1 of chromium (III) species, the rate of conversion was found to be 3% after 24 h exposure, 8% after 48 h, 10% after 72 h and no further conversion was observed thereafter. However, in a solution containing air sample matrix, 9.3% of chromium (III) converted to chromium (VI) within 6 h, and during the course of a 11-day exposure period, 13% (range 8–17%) of chromium (III) converted to chromium (VI). The method detection limit (MDL) for chromium (VI) in potassium hydroxide solution (0.025 M) was found to be 2×10−2 μg l−1. This is equivalent to 0.2 ng m−3 (for 23 m3 air sampled into 200 ml of KOH solution over a 24-h period). The recovery of spiked chromium (VI) from solutions containing air sample matrix was 95±9% (n=8). Matrix related interferences were estimated to be less than 10% based on recovery studies. The concentration of airborne chromium (VI) in Sydney residential areas was found to be less than 0.2 ng m−3, however, in industrial areas the concentrations ranged from 0.2 to 1.3 ng m−3 using this analytical procedure. 相似文献
90.
A new class of Salpen analogues based on phosphorus derivatives where the classical alkylene backbone has been replaced by a N-P-N linkage is described. Such linkage both affords a very good stability in water and an additional (fifth) potentially complexing site. The classical ortho-OH groups have been also replaced by various ortho-substituents, including diphenylphosphino groups. The synthesis of these compounds is easy and their structure can be varied at will at several levels. Several ways of synthesis can be used to combine the various fragments constituting these Salpen analogues. The structure of one of these fragments, an azide, was determined by X-ray crystallography. A preliminary study of the complexation ability of some of these new ligands was carried out with groups 10 (Ni) and 11 (Au) elements. Depending on the type of substituents and the type of metals used, these compounds can act as mono-, or tetra-dentate ligands. 相似文献