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71.
A capillary electrophoresis (CE) with UV absorption detection method is described for the simultaneous determination of glufosinate, glyphosate, and aminomethylphosphoric acid. The 9‐fluorenylmethyl chloroformate (FMOC‐Cl) was used for precolumn derivatization of the non‐absorbing herbicides. The three analytes were separated by CE in 9 min with 25 mM borate buffer at pH 9, followed by detection with a UV detector at 260 nm. We demonstrate how the detection limit can be enhanced by using acetonitrile‐salt mixtures. With acetonitrile‐salt mixtures, the limit of detection (LOD) was in the 10?7 M range. Linearity of more than two orders of magnitude was generally obtained. Precisions of migration times and peak areas were less than 0.9% and 7.5%, respectively. The applicabilities of the method for the analysis of ground water and lake water were examined. 相似文献
72.
The separation and selectivity of eight aromatic compounds ranging from hydrophilic to hydrophobic properties in micellar electrokinetic chromatography (MEKC) using sodium dodecyl sulfate (SDS) micelles or Tween 20-modified mixed micelles were investigated. The effect of different operation conditions such as SDS and Tween 20 modifier surfactant concentration, buffer pH, and applied voltage was studied. The resolution and selectivity of analytes could be markedly affected by changing the SDS micelle concentration or Tween 20 content in the mixed micelles. Applied voltage and pH of running buffers were used mainly to shorten the separation time. Complete separation of eight analytes could be achieved with an appropriate choice of the concentration of SDS micelles or Tween 20-modified mixed micelles. Quicker elution and better precision could be obtained with SDS-Tween 20 mixed micelles than with SDS micelles. The mechanisms that migration order of those analytes was mainly based on their structures and solute-micelle interactions, including hydrophobic, electrostatic, and hydrogen bonding interactions, were discussed. 相似文献
73.
The use of capillary electrophoresis (CE) with laser-induced fluorescence excited by ultraviolet (UV) lasers in the range 200–300 nm has been restricted by the available wavelengths and expense of UV lasers. The integration of a NeCu deep UV laser operating at 248.6 nm with a single channel CE system with post-column sheath flow detection allows detection limits for serotonin and tryptophan of 3.9×10-8 M and 4.5×10-8 M respectively. Single cell analysis of serotonergic metacerebral cells from the sea slug Aplysia californica yields a value of 800±85 fmol of serotonin in each cell soma. For the first time, serotonin is directly detected in electrically stimulated release from single metacerebral cell soma, with approximately 4% of the serotonin contained in the soma released from a semi-intact preparation with a 2 min electrical stimulation. 相似文献
74.
YanXiaCAO MiaoDU QiangZHENG 《中国化学快报》2004,15(5):567-570
The study on rheological properties of a series of mica-filled polypropylene (PP) composites was carried out. The influence of surface-treatment of mica particles on dynamic rheological behavior of the composites were dealt with. The viscosity (η) and dynamic modulus ( G‘ ) of the composite melts were higher than those of PP matrix, especially those for systems treated with silane, which was attributed to the interfacial adhesion enhancement. However, surface-treatment of mica by titanate resulted in lower η and G‘, as compared with the treatment by silane. The reason for this is believed to be the formation of the mono-molecular layer on the mica surface. 相似文献
75.
The effect of pH on the adsorption of anionic dye Titan yellow on the activated carbon from aqueous solution has been studied. It has been found that the Zeta potential of the activated carbon has a great effect on adsorption capacity of Titan yellow. The kinetic and the thermodynamic parameters of adsorption as a function of pH has been evaluated. The mechanism for adsorption of anionic dye Titan yellow on the activated carbon has also been discussed. 相似文献
76.
Li Shu-Min Miao Yan-Gang Zhou Zi-Fang Chen Ji Liu Yao-Yang 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1997,39(1):29-34
The first Born approximation is used to study the laser-assisted electron capture by a fast proton from a hydrogen atom. The laser modification on differential cross section peaks sharply in the forward direction. With the impact energy increasing, the change in integral cross section becomes notable. The more intense the laser, the greater the cross section is; the lower the frequency, the greater the cross section. 相似文献
77.
Hydrophobically associating copolymers of acrylamide (AM) with a small amount of 4-(omega-propenoyloxyethoxy) benzoic acid (PEBA, <2.5%) were synthesized by template copolymerization in the presence of poly(allylammonium chloride) (PAAC) as a template in an aqueous medium. These template copolymers exhibited remarkable thickening properties due to the effective hydrophobic association, which were similar to those copolymers with a multiblock structure obtained by the micellar process. The pH of the reaction medium and the molecular weight of the template strongly influenced the thickening properties of the products. In the experimental range, the higher the PEBA content, the larger the thickening capacity of these hydrophobic copolymers. The aggregate behaviors of these copolymers were studied by fluorescence, transmission electron microscopy (TEM), and light scattering techniques. The apparent critical interpolymer aggregate concentration (cac) of the copolymer solution was about 0.5 g/dL. As the concentration of the copolymer became higher than the cac, the aggregates changed their morphology from small hollow spheres to big flower-shaped aggregates. All the above results indicated that the template copolymerization gave access to a very simple and powerful means for the preparation of hydrophobically associating copolymers and other functional polymer materials. 相似文献
78.
The construction of two unique, high-nuclearity Cu(II) supramolecular aggregates with tetrahedral or octahedral cage units, [(mu(3)-Cl)[Li subset Cu(4)(mu-L(1))(3)](3)](ClO(4))(8)(H(2)O)(4.5) (1) and [[Na(2) subset Cu(12)(mu-L(2))(8)(mu-Cl)(4)](ClO(4))(8)(H(2)O)(10)(H(3)O(+))(2)](infinity) (2) by alkali-metal-templated (Li(+) or Na(+)) self-assembly, was achieved by the use of two newly designed carboxylic-functionalized diazamesocyclic ligands, N,N'-bis(3-propionyloxy)-1,4-diazacycloheptane (H(2)L(1)) or 1,5-diazacyclooctane-N,N'-diacetate acid (H(2)L(2)). Complex 1 crystallizes in the trigonal R3c space group (a = b = 20.866(3), c = 126.26(4) A and Z = 12), and 2 in the triclinic P1 space group (a = 13.632(4), b = 14.754(4), c = 19.517(6) A, alpha = 99.836(6), beta = 95.793(5), gamma = 116.124(5) degrees and Z = 1). By subtle variation of the ligand structures and the alkali-metal templates, different polymeric motifs were obtained: a dodecanuclear architecture 1 consisting of three Cu(4) tetrahedral cage units with a Li(+) template, and a supramolecular chain 2 consisting of two crystallographically nonequivalent octahedral Cu(6) polyhedra with a Na(+) template. The effects of ligand functionality and alkali metal template ions on the self-assembly processes of both coordination supramolecular aggregates, and their magnetic behaviors are discussed in detail. 相似文献
79.
A density functional theory investigation on a series of sandwich-type transition metal complexes [(CBO)n]2M (n=4–6; M=transition metals) with carbon boronyls (CBO)n as effective aromatic ligands has been presented in this work at B3LYP level. The ground-states of these complexes possess staggered Dnd symmetries, while the corresponding eclipsed Dnh structures exist as transition states with slightly higher energies (within 5.8 kJ/mol). Carbon boronyl complexes [(CBO)n]2M are confirmed to be much more stable than their boron carbonyl isomers [(BCO)n]2M, which, on the other hand, take eclipsed ground-states with Dnh symmetries. The carbon boronyl complexes [(BCO)n]2M proposed in this work parallelize the well-known sandwich-type hydrocarbon complexes [CnHn]2M in coordination chemistry with boronyl groups –BO isolobal to –H atoms in corresponding ligands. 相似文献
80.
A unique cyano-bridged copper(II)-copper(I) mixed-valence polymer, {[Cu(3)(CN)(4)(H(2)O)(3)](H(2)O)(2)}(n) (1), has been prepared and structurally determined by X-ray diffraction. The cyanide anions with (mu(2),eta(2)) and (mu(3),eta(2)) bridging modes connect the copper centers into a complicated zeolite-like 3-D network. Of further interest, coordinated and lattice water molecules in this structure form 1-D hydrogen-bonded water tapes consisting of linked cyclic pentamer clusters. 相似文献