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921.
Analysis of herbicides in water using temperature-responsive chromatography and an aqueous mobile phase 总被引:1,自引:0,他引:1
Ayano E Okada Y Sakamoto C Kanazawa H Okano T Ando M Nishimura T 《Journal of chromatography. A》2005,1069(2):281-285
A simple and rapid method has been developed for herbicides in water using temperature-responsive liquid chromatography (LC) and a column packed with poly(N-isopropylacrylamide) (PNIPAAm), a polymer anchored on the stationary-phase surface of modified silica. PNIPAAm reversibly changes its hydrophilic/hydrophobic properties in water in response to temperature. The method was used to determine five sulfonylurea and three urea herbicides. Separation was achieved with a 10 mM ammonium acetate (pH 3.0) isocratic aqueous mobile phase, and by changing the column temperature. The analytes were extracted from water by off-line solid-phase extraction (SPE) with an N-vinyl-pyrrolidone polymer cartridge. The average recoveries of the eight herbicides from spiked pure water, tap water and river water were 70-130% with relative standard deviations (RSDs) of <10%. The limits of quantitation (LOQ) of the eight herbicides were between 1 and 4 microg l(-1). 相似文献
922.
Masayuki Yamaguchi Koh‐Hei Nitta Akira Tanaka Mitsunobu Kitamura 《Journal of Polymer Science.Polymer Physics》1999,37(13):1513-1521
The characterization of the mechanical nonlinear behavior of isotactic polypropylene/ethylene‐1‐hexene copolymer blends with various kinds of morphology was carried out using a nonlinear constitutive equation in which the plastic deformation and the anharmonicity of elastic response are taken into account. It was found that the mechanical nonlinearity of the incompatible blends showing phase separation is much greater than that of the compatible blends having rubbery components in the interlamellar regions. Moreover, the mechanical behavior is governed by the plastic deformation for the incompatible blends, whereas the anharmonicity strongly affects the mechanical behavior for the compatible blends. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1513–1521, 1999 相似文献
923.
Yoichi Yamaguchi 《International journal of quantum chemistry》1997,62(4):393-401
The geometric and electronic structures of n-tetrasilane cation and anion radicals as models of doped linear polysilanes are studied theoretically using an ab initio molecular orbital method at the UMP2/6–31 + G(d, p) level of calculations. It is found that the trans-conformations in these molecules are the most stable structures in each ground state and that the energy differences between the cis- and trans-conformations are 3 kcal/mol for the cation radical and 11 kcal/mol for the anion radical. There exists no stable gauche-conformation in these molecules in contrast to neutral n-tetrasilane. It seems that the weakening of the central silicon-silicon bond on doping is connected to the concentration of the charge distributions on central silicon atoms with the change from trans- to cis-conformations in both n-tetrasilane cation and anion radicals. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 62 : 393–401, 1997 相似文献
924.
Organorhodium complexes, such as RhH(PPh3)4, RhH(CO)(PPh3)3, Rh(η3-C3H4Ph)(CO)(PPh3)2, and RhH(dppe)2 [dppe = 1,2-bis(diphenylphosphinoethane)], catalyze polymerization of phenylallene and of 4-methylphenylallene at 60 °C. High-molecular-weight polymers (Mn>4×105) are isolated from the reaction products by removing the low-molecular-weight (Mn<3×103) acetone-soluble fraction. The NMR (1H and 13C{1H}) spectra of poly(phenylallene) (1) and poly(4-methylphenylallene) (2) show the structure formed through selective 2,3-polymerization of the monomers, while similarly obtained poly(2-naphthylallene) (3) is characterized only by 1H NMR spectroscopy due to its low solubility in common organic solvents. 4-Fluorophenylallene and 4-(trifluoromethyl)-phenylallene do not polymerize under similar conditions in the presence of RhH(PPh3)4 catalyst but are turned into low-molecular-weight oligomers. CoH(N2)(PPh3)3-catalyzed polymerization of phenylallene and 4-methylphenylallene at room temperature gives the corresponding polymers with molecular weights in the range Mn=(9–15)×104, in high yields. © 1997 John Wiley & Sons, Ltd. 相似文献
925.
Isao Yamaguchi Takahiro Kimishima Kohtaro Osakada Takakazu Yamamoto 《Journal of polymer science. Part A, Polymer chemistry》1997,35(7):1265-1273
RuH2(PPh3)4 catalyzed Tishchenko type polyaddition of terephthal-aldehyde gives aromatic polyester ( 1 ), which contains three structural units, [OCH2 C6H4 CH2O] ( 1a ), [OCH2 C6H4 CO] ( 1b ), and [CO C6H4 CO] ( 1c ). 1H-NMR spectrum shows the presence of the three units in a 1 : 2 : 1 ratio. Isophthalaldehyde also undergoes similar polyaddition to give another aromatic polyester ( 2 ), while 1,12-dodecanedial gives an aliphatic polyester ( 3 ) containing the following structural units: [OCH2 (CH2)10 CH2O] ( 3a ), [OCH2 (CH2)10 CO] ( 3b ), and [CO (CH2)10 CO] ( 3c ). The above polymers have Mn of 2.7 × 103−5.4 × 103 and Mw of 4.3 × 103 − 9.7 × 103, respectively. Mixtures of terephthalaldehyde and 1,12-dodecanedial produce copolymers, which contain the units 1a–1c and 3a–3c in a random sequence. In the copolymerization, terephthalaldehyde shows a strong tendency to give 1c units, whereas 1,12-dodecanedial predominantly affords 3a units. SmI2 also catalyzes polyaddition of terephthalaldehyde to give the corresponding polyester with Mn of 1.7 × 103 and Mw of 3.7 × 103, respectively. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1265–1273, 1997 相似文献
926.
927.
Nori Yamaguchi Devdatt S. Nagvekar Harry W. Gibson 《Angewandte Chemie (International ed. in English)》1998,37(17):2361-2364
Like the proverbial monkey chain one heteroditopic self-complementary molecule, comprising a crown ether unit and a paraquat unit, catches a second such molecule in solution and thus by self-organization forms novel linear oligo- and polymolecular arrays (shown schematically; the crown ether unit is denoted by the ellipse, and the paraquat unit by the rectangle). 相似文献
928.
Makoto Fujita Shu-Yan Yu Takahiro Kusukawa Hidenori Funaki Katsuyuki Ogura Kentaro Yamaguchi 《Angewandte Chemie (International ed. in English)》1998,37(15):2082-2085
Nanometer-sized bowls: six metal centers and four tridentate ligands self-assemble in aqueous solution to give the macrotricycle 1 , which has approximate dimensions of 3×2×2 nm. Another macrocycle (not shown), obtained with a different ligand, is of similar size and topology but differs considerably from 1 in its host–guest behavior. 相似文献
929.
930.
Yoichi Yamaguchi Yosuke Nagasawa Akinori Murakami Kenji Tabata 《International journal of quantum chemistry》1998,69(5):669-678
The stability of oxygen anions and the hydrogen abstraction from methane on a reduced SnO2 (110) crystal surface have been studied theoretically using a point-charge model. The geometric and electronic structures for the present molecules are calculated by means of a hybrid Hartree–Fock/density functional method at the B3LYP/6-311+G(3df, 3pd) level of theory. The calculations of the energies on the point-charge model are performed using these optimized geometries. It is found that a low concentration of the active oxygen species O− and O2− is expected on the reduced SnO2 surface. The activation energies for the abstraction of hydrogen atom from methane on the reduced SnO2 surface are obtained: 12 kcal/mol for O− species and more than 48 kcal/mol for O2− species, indicating that O− species on the surface is the main active center for the dissociation of a C(SINGLE BOND)H bond of methane, which is in agreement with the other oxide catalysts. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 69: 669–678, 1998 相似文献