共查询到20条相似文献,搜索用时 15 毫秒
1.
Reed M. Izatt 《Journal of inclusion phenomena and macrocyclic chemistry》1997,29(3-4):197-220
Research in selective ion separations at Brigham Young University hasinvolved the use of liquid membranes of the bulk, emulsion, thin sheetsupported, hollow fiber supported, and two-module hollow fiber supportedtypes as well as solid phase extraction using immobilized ligands. By use ofdesigned cation and anion selective macrocyclic ligands, it has beenpossible to accomplish a wide range of interesting separations. Theprinciples underlying the separations and a comparison of the advantages anddisadvantages of the various systems are given. Some of the solid phaseextraction systems have been commercialized by IBC Advanced Technologies,Inc. Examples of commercial applications are presented in the analytical,environmental, metallurgical, precious metals, and nuclear waste areas. 相似文献
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Molecular shape can provide a basis for chromatographic separations that is distinct from other interaction mechanisms often considered in liquid chromatography. Molecular shape recognition, or shape selectivity, is most evident for the separation of isomeric compounds that have constrained molecular structures, such as polycyclic aromatic hydrocarbons. A central feature of shape-selective columns is conformational order within the stationary phase; this aspect of stationary phase morphology is revealed through spectroscopic studies and molecular dynamics simulations, and is correlated with chromatographic performance.
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《液相色谱法及相关技术杂志》2012,35(12):2271-2292
Abstract Three 40 μm derivatized silicas, two aminoalkyl and one carboxyalkyl, have been compared to 40 μm silica gel for performance in normal phase preparative liquid chromatography. The three derivatives showed higher selectivity for compounds capable of hydrogen-bond formation or acid-base interactions. Retention times were related to the basicity of the amine bonded derivatives or the acidity of the carboxylic acid derivative and the pK values of the solutes. The advantages for each of the four sorbents for neutral, acidic and basic compounds have been described. 相似文献
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Due to the importance of chiral separations of drugs, pharmaceuticals, agrochemicals and xenobiotics by high performance liquid
chromatography (HPLC) and capillary electrophoresis (CE), it is important to have the knowledge of the enantiomeric recognition
mechanisms so that scientists may design and module the new chiral selectors for rapid, inexpensive and reproducible chiral
separations; specially at preparative scale. The mechanisms of the chiral separation by HPLC and CE using polysaccharides,
cyclodextrins, macrocyclic glycopeptide antibiotics, Pirkle type, ligand exchangers, crown ethers and other several types
of chiral selectors have been discussed. Various complex formation and different types of interactions responsible for chiral
resolution have been presented in detail. 相似文献
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《Analytical letters》2012,45(8):1787-1797
Abstract Mixture Design and a Chromatographic Response Function were used to study the effect of different organic solvents as modifiers on the Reversed Phase (C-18) High Performance Thin Layer Chromatographic separation of three amino acid hydroxamates (Arginine hydroxamate, Threonine hydroxamate, and Histidine hydroxamate). Both 3 solvent (methanol, acetonitrile and tetrahydrofuran) and 4 solvent (methanol, acetonitrite, tetrahydrofuran and acetone) systems were studied. 相似文献
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《Analytical letters》2012,45(4):161-167
Abstract Amino acid responsive electrodes based on the use of their quaternary ammonium salts in a liquid membrane phase have been prepared for tryptophane, phenylalanine, leucine, methionine, valine, and glutamic acid. 相似文献
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J. D. Henry Jr. M. E. Prudich K. R. Vaidyanathan 《Separation & Purification Reviews》2013,42(2):81-118
The removal of the mineral matter found in coal derived liquids is a very difficult solid/liquid separation process. Clays, pyrites and other minerals that occur in coal ultimately find their way into the liquefied product. This is the case, e.g., for both the solvent refined coal (SRC-I) and H-Coal processes. The ash content of bituminous coals which may be fed to coal liquefaction processes normally rangesfrom 6 to 11 wt.%. The ash content of the coal liquid product can range from 4 to 20 wt.% depending upon the lique-faction .process. Ash levels must be reduced to, e.g., 0.4 wt.% in the case of boiler fuel and less than 0.1 wt.% for gas turbine fuels. 相似文献
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《液相色谱法及相关技术杂志》2012,35(8):1783-1790
Abstract The separation of cyclic nitros amines by HPLC was achieved using a cyclobond I column and a mobile phase of methanol/water. The effect of in-the-ring and on-the-ring substitutions on retention times were studied. The results show that the longer the chain of the substituent, the longer the retention time, which is consistent with the inclusion mechanism of separation. Also, the larger the ring, the longer the retention time. The results also show that the in-the-ring substitution has a dramatic effect on retention. 相似文献
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《液相色谱法及相关技术杂志》2012,35(12):2763-2779
Abstract The separation of acyclic nitrosamines by HPLC using a β-cyclodextrin bonded silien gel column and a C18 reversed phase column was evaluated. Four groups of nitrosamines were used to evaluate the utility of both columns: (1.) methylmethyl-, methylethyl-, methylpropyl and methylbutyl-; (2.) ethylmethyl-, ethylethyl-, and ethylpropyl-; (3.) propylmethyl-, propylpropyl-, and propylbutyl-; and (4.) butylmethyl-, butylethyl-, butylpropyl-, and butylbutyl nitrosamines. The results show that both columns performed well in separating the nitrosamines in each group, with the C18 column requiring a higher percentage of organic modifier (methanol) than the β-cyclodextrin column. The β-cyclodextrin column was superior in separating all the E to Z isomers of short chain alkyl nitrosamines, while the C18 column was superior in separating long alkyl chain nitrosamines and their E and Z isomers. It, was also found that, the longer the alkyl chain the longer the retention time, while nitrosamines having the same number of carbons, for example ethylbutyl-and propylpropyleluted at virtually the same time, using both columns. 相似文献
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《Analytical letters》2012,45(5):1221-1235
Abstract Anomalies in the theory of mass transport-determined liquid membrane ISE response have been identified and corrected where possible. an early model of the response has been corrected in light of recent results. the resultant mass transport equations were shown incapable of describing the experimental root time dependence of the response curves, unless other phenomena (e.g., Donnan failure) simultaneously influenced the potential. 相似文献
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L. Chimuka M. M Nindi J. Å Jönsson 《International journal of environmental analytical chemistry》2013,93(4):429-445
Abstract A method for sample work-up and enrichment using Supported Liquid Membrane (SLM) and liquid chromatographic determination of triazine herbicides in natural waters was investigated. A porous PTFE membrane was impregnated with a water immiscible organic solvent, forming a barrier between two aqueous phases. With a flowing donor and a stagnant acceptor solution, an enrichment of the triazines was obtained. The various factors that influence the extraction efficiency and selectivity of the extraction procedure were experimentally studied. The obtained results were in good agreement with the developed theoretical model. The pH of the acceptor solution was found to be the critical limiting factor in obtaining higher extraction efficiencies and led to an extraction efficiency decrease with an increase in enrichment time. By increasing both the trapping capacity of the acceptor solution and the donor flow rate, the method detection limit of the triazines ranged from 0.03 to 0.16 μgL?1 in natural waters with 20 minutes extraction time. 相似文献
15.
《液相色谱法及相关技术杂志》2012,35(6):1069-1080
Abstract Separations in thin layer (TLC) and high performance liquid chromatography (HPLC) using alkyl bonded phases were carried out under optimum solvent conditions for each of three phases, RP-2, RP-8 and RP-18. The phases were tested for their efficiency and resolving power using three groups of compounds in three binary organic-water mobile phases. The organic solvents were acetonitrile, methanol and tetrahydrofuran, which are widely used as solvent modifiers in reversed phase liquid chromatography. The results showed that, unlike HPLC, TLC using RP-18 plates was the most, and RP-2 plates the least, efficient. A naphthalene and biphenyl mixture which was resolved by HPLC using any of the three solvents and columns was not resolved by TLC using any plate or solvent combination, unless the plate was prewashed with an organic modifier. The addition of NaCl (1–2% wt/vol) to the solvent for TLC speeded development unless an alcohol was used, but did not greatly affect the separation. 相似文献
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An automated sample pretreatment of human blood plasma for liquid chromatographic determination of three antidepressant drugs, dibenzepine; a tricyclic antidepressant (TCA), reboxetine; a selective noradrenaline reuptake inhibitor (SNRI) and fluvoxamine; a selective serotonin reuptake inhibitor (SSRI), based on supported liquid membrane (SLM) for unsurpassed sample clean-up and analyte enrichment, has been developed. The chromatograms after enrichment of plasma blank and aqueous blank are virtually indistinguishable. The entire analytical procedure revealed good linearity and low detection limits of 5, 15 and 20 ng mL–1 for dibenzepine, reboxetine and fluvoxamine, respectively. No carry-over effects were noted. The repeatability of extraction at three concentrations in the range 40–150 ng mL–1 for the three drugs was between ca. 3% and 7% as relative standard deviation. The reproducibility relative standard deviation during three different days (replacing the membrane each day) was not significantly higher. 相似文献
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G. B. S. Salaria 《Fresenius' Journal of Analytical Chemistry》1961,180(5):358-360
Summary It has been shown that it is possible to separate and estimate quantitatively platinum, rhenium, gold or pentavalent antimony from zirconium by decomposing the thiosalts, formed by these elements with 2 N sodium sulphide reagent, with hydrochloric acid.Part I: Salaria, G. B. S.: Z. analyt. Chem. 179, 91 (1961). 相似文献
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