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981.
The fabrication and electrochemical characteristics of a penicillamine (PCA) self-assembled monolayer modified gold electrode were investigated. The self-assembled electrode shows obvious electrocatalytic activity for the oxidation of epinephrine (EP). In phosphate buffer (pH 7.73), a sensitive oxidation peak was observed at 0.190V with the PCA modified Au electrode. The peak current is proportional to the concentration of EP in the range of 2.0×10–56.0×10–4molL–1 and 5.0×10–6 2.0×10–4molL–1 for cyclic voltammetry (CV) and differential pulse voltammetry (DPV) with the detection limits of 1.8×10–7 and 1.3×10–7molL–1, respectively. The possible reaction mechanism is also discussed. The PCA self-assembled monolayer modified gold electrode is highly stable and can be applied to the determination of EP in practical injection samples. Application is simple, rapid and produces accurate results. 相似文献
982.
Ya‐Ching Shen ChengLin Lee AshrafTaha Khalil Yuan‐Bin Cheng Ching‐Te Chien Yao‐Haur Kuo 《Helvetica chimica acta》2005,88(1):68-77
Bioassay‐guided fractionation of an AcOEt extract of Casearia membranacea resulted in the isolation of six new clerodane diterpenes, caseamembrins G–L ( 1 – 6 ). The structures of the new compounds, including their relative configurations, were established by an extensive study of their spectral data, especially 2D NMR. The cytotoxic activities of the isolated diterpenes against human oral epidermoid (KB), cervical epitheloid (Hela), and liver (Hep59T/VGH) carcinoma cell lines were investigated. 相似文献
983.
A pressure-filter-template approach was employed to prepare polyelectrolyte nanotubes through layer-by-layer deposition in the alumina template. With the thicker wall, the ordered polymer nanotubes possess a high flexibility. The results demonstrate that the electrostatic interactions of polyelectrolytes play a key role in fabricating water-soluble charged polymer nanotubes. The structure of the polyelectrolyte nanotube was confirmed by SEM, TEM, and UV, respectively. 相似文献
984.
Yi‐Jun Huang Guo‐Rong Qi Yu‐Hua Wang 《Journal of polymer science. Part A, Polymer chemistry》2002,40(8):1142-1150
A double metal‐cyanide catalyst based on Zn3[Co(CN)6]2 was prepared. This catalyst is very effective for the ring‐opening polymerization of propylene oxide. Polyether polyols of moderate molecular weight having low unsaturation (<0.015 meq/g) can be prepared under mild conditions. The molecular weight of polymer is entirely controlled by a reacted monomer‐to‐initiator ratio. The polymers prepared with stepwise addition of monomer exhibit a narrower molecular weight distribution as compared with those prepared with one‐step addition of monomer. Various compounds containing active hydrogen, except basic compounds and low‐carbon carboxylic acid, may be used as initiators. The reaction rate increases with increasing catalyst amount and decreases with rising initiator concentration. Polymerization involves a rapid exchange reaction between the active species and the dormant species. It was also proven that, to a certain extent, the chain termination of this catalytic system is reversible or temporary. 13C NMR analysis showed that the polymer has a random distribution of the configurational sequences and head‐to‐tail regiosequence. It is assumed that the polymerization proceeds via a cationic coordination mechanism. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1142–1150, 2002 相似文献
985.
N. S. Mosyagin A. V. Titov R. J. Buenker H.‐P. Liebermann A. B. Alekseyev 《International journal of quantum chemistry》2002,88(5):681-686
Multireference single‐ and double‐excitation configuration interaction (MRD‐CI) calculations of transition energies for the Hg atom and spectroscopic constants for the HgH molecule are carried out with the generalized relativistic effective core potential (GRECP) method. A new selection criterium for the reference configurations is discussed. The calculated spectroscopic constants are compared with experimental data and results of calculations of other groups. Improvement of accuracy is mainly observed for bond lengths from the GRECP/MRD‐CI calculations (without applying the T = 0 correction) with respect to the results of other groups. Analysis of the quality of the approximations employed is carried out. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 相似文献
986.
The reactions of transition metal salts with taurine 5‐chlorosalicylaldelyde Schiff base gave two complexes [Ni(TCSSB)(H2O)3].H2O (1) and [Cu(TCSSB)(H2O)2]2[Cu(TCSSB)2].6H2O (2) (TCSSB=taurine‐5‐chlorosalicylaldelyde Schiff base), which were characterized by elemental analysis and X‐ray diffraction analysis. The complex 1 crystallized in monoclinic system with space group P2 1/c, and a=1.4816(2) nm, b=1.3953(2) nm, c= 0.7466(1) nm, β= 100.499(3)°, V=1.5176(4) nm3, Z=4, and an infinite 3‐D network structure was formed by hydrogen bonds among sulfo group, crystal water and coordinated water. Complex 2 crystallized in triclinic system with space group P1 , with the cell parameters: a = 0.6413(2) nm, b= 1.4596(3) nm, c= 1.6188(4) nm, a= 102.473(5)°, β= 98.979(4)°, γ=101.739°, V=1.4165(6) nm3, Z=1. The coordination environment between Cu(1) and Cu(2) is different. Cu(1) is slightly distorted square pyramidal while Cu(2) is distorted square‐plane. The complex 1 is mononuclear while the complex 2 is made up of two coordinated subunits, namely [Cu(TCSSB)2] and [CU(TCSSB)(H2O)2]2. Besides that the TG‐DTG of the complex 1 was analyzed, the thermal decomposition reaction of the complex was studied under a non‐isothermal condition by TG‐DTG. The TG and DTG curves indicate that the complex was decomposed in three stages: . 相似文献
987.
Qi‐Wei Zhang Yi‐Hang Wen Yun‐Long Feng 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(6):m255-m257
The title compound, [Zn2(C5H6O4)2(C13H14N2)]n or [Zn2(glu)2(bpp)]n, is a novel zinc polymer based on mixed flexible glutarate (glu) and 1,3‐di‐4‐pyridylpropane (bpp) ligands. The ZnII center has a distorted tetrahedral geometry and the central atom of the bpp ligand is located at a special site with a C2 axis passing through it. A layer is formed by Zn–glu bonding. Such layers are pillared by bpp ligands, forming a three‐dimensional framework with large channels. The inverted interpenetration of two three‐dimensional frameworks completes the molecular structure. 相似文献
988.
Capillary electrochromatography (CEC) has been performed with a series of C14, methlyacrylamide based monolithic columns. These monoliths with different porosities were prepared by in-situ copolymerization in fused-silica capillaries. The porous properties of monoliths were further observed using scanning electron micrographs (SEM) and measured using a mercury porosimeter. The effect of various alcohols as porogens on porous structural properties and chromatographic behaviors were also investigated. The effects of organic additive, pH value and ionic strength in mobile phase on electroosmosis flow (EOF) and separation were further discussed. Meanwhile, the baseline separation of 6 neutral compounds can be well obtained. In addition, the monolithic column demonstrates the high column efficiency and satisfactory reproducibility.Acknowledgements We gratefully acknowledge the support of the National Natural Science Foundation of China. 相似文献
989.
990.
Yan Xiao Jian Wang Wang Xia Guang Feng Huai You Wang 《Journal of Analytical Chemistry》2007,62(5):438-443
The maximum emission wavelength of dopamine is 317 nm with excitation at 290 nm. The relative fluorescence intensity of dopamine
decreased in the presence of enoxacin, which showed that fluorescence quenching occurred. The Stern-Volmer (S-V) plot showed
a nonlinear relationship between the relative fluorescence intensity of dopamine and the concentration of enoxain. The quenching
mechanism was studied and the results suggested that both dynamic and static quenching processes were responsible for the
observed positive deviation in the S-V plot. When the S-V plot was modified by logarithm, the linear relationship was obtained
between logF
0/F and C in the range of 0.10 to 13.0 μg/mL (where F
0 is the relative fluorescence intensity of dopamine, F is the relative fluorescence intensity of dopamine in the presence of enoxacin, and C is the concentration of enoxacin). The fluorescence quenching method for the determination of enoxacin was developed. The
linear regression equation of the calibration graph of enoxacin was C = 13.70 (logF
0/F) − 0.5836, with the correlation coefficient 0.9984. The detection limit was 2.0 ng/mL and the relative standard deviation
was 2.52%. The effects of pH, the stability of dopamine in the presence of enoxacin, and foreign ions on the determination
of enoxacin have been examined. The recovery of enoxacin was from 94.9 to 103.0% in a human serum sample and from 94.9 to
108.0% in a urine sample. The method is simple, rapid, and can be used for the determination of enoxacin in human serum and
urine samples with satisfactory results.
The text was submitted by the authors in English. 相似文献