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991.
A sensitive and specific method was developed for the determination of sophoridine (SRI), sophocarpine (SC) and matrine (MT) in rabbit plasma by HPLC-MS. After an administration of Kuhuang by injection, blood samples were collected and extracted with methanol. The extract solutions were analysed by HPLC-MS method. The separation was performed on a ZORBAX Extend-C18 column using methanol/water/diethylamine (50:50:0.07, v/v/v) as mobile phase. The quinolizidine alkaloids were detected by using mass spectrometry in the SIM mode. There was a good linear relationship between peak area and concentration of analytes over the concentration range of 13.2–995.0 ng mL–1 for SRI, 7.0–530.0 ng mL–1 for SC and 8.8–655.0 ng mL–1 for MT, respectively. The absolute recovery of this method was more than 57% for SRI, 87% for SC and 91% for MT. The accuracy of assay was more than 90%. The limits of detection (LODs) were 6.8 ng mL–1 for SRI, 3.5 ng mL–1 for SC and 4.2 ng mL–1 for MT, respectively. The limits of quantitation (LOQs) were 13.2 ng mL–1 for SRI, 7.0 ng mL–1 for SC and 8.8 ng mL–1 for MT, respectively. The intra-day and inter-day coefficients of variation (RSDs) were less than 10.1, 6.3 and 5.8% for SRI, SC and MT, respectively. The developed method was applied to determine the concentration–time profiles of SRI, SC and MT in rabbit plasma after injection of Kuhuang. 相似文献
992.
A new ligand H2L, 1,7-di(1-phenyl-3-methyl-5-pyrazolone-4-benzylidene)diethenetriamine and its three transition metal complexes, ML · nH2O [M=Cu(II), n=2; M=Zn(II), n=0.5; M=Ni(II) (1), n=3] have been synthesized in anhydrous EtOH and characterized on the basis of elemental analyses, molar conductivities, i.r.
spectra, u.v. spectra and thermal analyses. In addition, the DNA-binding properties of the ligand and its complexes have been
investigated by absorption, fluorescence and viscosity measurements. The experimental results indicated that the ligand and
the complex (1) can bind to DNA , but the other two complexes can’t; the binding affinity of the complex (1) is higher than
that of the ligand and the intrinsic binding constant kb of the complex (1) is 7.893×105 m−1. 相似文献
993.
Osei-Twum EY Litorja LA Darkwa J Maisela LL Lesimple A Mamer O 《Journal of the American Society for Mass Spectrometry》2005,16(1):94-99
The mass spectral behavior of a number of organometallic complexes containing the Group 10 metals Ni, Pd, and Pt, together with various thiolate ligands were studied. For Pd, two main types of complexes, differing by the substituents on the phosphorus atom were studied. Types I and II were substituted with bis(diphenylphosphino)ferrocene and bis(diisopropylphosphino)ferrocene ligands, respectively. The Ni complexes, except for one, and the Pd Type I complexes had no molecular radical cations (M(+.)) in their EI spectra. On the other hand, all the Pt complexes showed intense M(+.) ions in their EI spectra indicating that these complexes were more stable as radical cations than those of Ni and Pd. The FAB and MALDI spectra of all the complexes displayed intense quasi-molecular ions (MH(+)) and the fragmentations in both modes were similar. The MALDI spectra of several complexes displayed only M(+.) ions while one gave evidence of both MH(+) and M(+.) ions. Several Pd Type II complexes yielded intense M(+.) in their EI spectra. 相似文献
994.
Tan C Atas E Müller JG Pinto MR Kleiman VD Schanze KS 《Journal of the American Chemical Society》2004,126(42):13685-13694
The conjugated polyelectrolyte PPESO3 features a poly(phenylene ethynylene) backbone substituted with anionic 3-sulfonatopropyloxy groups. PPESO3 is quenched very efficiently (KSV > 10(6) M(-1)) by cationic energy transfer quenchers in an amplified quenching process. In the present investigation, steady-state and picosecond time-resolved fluorescence spectroscopy are used to examine amplified quenching of PPESO3 by a series of cyanine dyes via singlet-singlet energy transfer. The goal of this work is to understand the mechanism of amplified quenching and to characterize important parameters that govern the amplification process. Steady-state fluorescence quenching of PPESO3 by three cationic oxacarbocyanine dyes in methanol solution shows that the quenching efficiency does not correlate with the Forster radius computed from spectral overlap of the PPESO3 fluorescence with the cyanines' absorption. The quenching efficiency is controlled by the stability of the polymer-dye association complex. When quenching studies are carried out in water where PPESO3 is aggregated, changes observed in the absorption and fluorescence spectra of 1,1',3,3,3',3'-hexamethylindotricarbocyanine iodide (HMIDC) indicate that the polymer templates the formation of a J-aggregate of the dye. The fluorescence dynamics in the PPESO3/HMIDC system were probed by time-resolved upconversion and the results show that PPESO3 to HMIDC energy transfer occurs on two distinctive time scales. At low HMIDC concentration, the dynamics are dominated by an energy transfer pathway with a time scale faster than 4 ps. With increasing HMIDC concentration, an energy pathway with a time scale of 0.1-1 ns is active. The prompt pathway (tau < 4 ps) is attributed to quenching of delocalized PPESO3 excitons created near the HMIDC association site, whereas the slow phase is attributed to intra- and interchain exciton diffusion to the HMIDC. 相似文献
995.
Cross-metathesis reactions of α,β-unsaturated sulfones and sulfoxides in the presence of molybdenum and ruthenium pre-catalysts were tested. A selective metahesis reaction was achieved between functionalized terminal olefins and vinyl sulfones by using the ‘second generation’ ruthenium catalysts 1c-h while the highly active Schrock catalyst 1b was found to be functional group incompatible with vinyl sulfones. The cross-metathesis products were isolated in good yields with an excellent (E)-selectivity. Both the molybdenum and ruthenium-based complexes were, however, incompatible with α,β- and β,γ-unsaturated sulfoxides. 相似文献
996.
?. Cerjan-Stefanovi? F. Bri?ki M. Ka?telan-Macan 《Fresenius' Journal of Analytical Chemistry》1991,339(9):636-639
Summary Waste waters of film processing plants are rich with silver. Part of the silver is regenerated electrochemically, but the rest (0.5 g) remains in waste waters and is sent to sewers. This is a bad politic from both the environmental (toxic waste waters) and the economical point of view (a waste of silver). In this work, the silver was isolated by ion-exchange resins and then concentrated by microorganisms. For exchange of silver, Ionenaustauscher I, II and IV were used. The batch method was used to obtain a static equilibrium. Silver elution from exchangers is based on silver transformation to a stable cation or anion complex. By varying the ligands, pH and eluent concentrations, optimum elution is found at 1 mol/l Na2S2O3, 1 mol/l NH3, 2 mol/l HNO3 and 1 mol/l (NH2)2CO. The concentration of silver in the eluent is about 50 mg/l. The silver ion uptake from solutions after ion exchange by mixed bacterial culture isolated from photographic waste water drain and pure bacterial cultures Escherichia coli 3009 and Bacillus subtilis 3053. was studied. Experiments were carried out in submerse culture at pH 7 with different Ag+ concentrations (4, 8 and 40 mg/l) on a rotary shaker (100 rpm) at 37°C. At the lower Ag+ concentrations a good growth and simultaneous removal of Ag+ from the solutions was achieved. At Ag+ concentration of 40 mg/l growth and removal of Ag+ by mixed and pure culture differed significantly. Thus mixed bacterial culture grew well and at the same time removed efficiently Ag+ (approximately 90%) from medium. Pure bacterial cultures on the contrary were unable to grow at 40 mg/l Ag+, though their biomass showed to be an effective biosorbent for Ag+ (approximately 80% of Ag+ removal). 相似文献
997.
An interface for a high-performance liquid chromatographic system based on the Commodore 64 personal computer has been designed as an alternative to the expensive and somewhat inflexible solvent programmers and data acquisition systems offered by commercial manufacturers. The system consists of the Commodore 64 with a single disk drive and monitor, and an interface that directly controls the flow-rates of two Waters pumps for solvent delivery in either isocratic or gradient mode, as well as analog-to-digital conversion of chromatographic data and either graphic data output to a dot-matrix printer or digital-to-analog conversion for output to a chart recorder. The interface permits computer-controlled flow-rates of up to 10.0 ml/min, with an accuracy of 0.0047 ml/min at flow-rates of 4.1 ml/min and an accuracy of 0.03 ml/min at flow-rates of 10 ml/min. The software for data analysis permits tabulation of elution times and areas for the peaks in a chromatogram with an option for baseline correction. The data are stored on floppy disks together with information pertinent to the chromatogram (flow-rate, solvent composition, etc.). 相似文献
998.
2-Trifluoroacetyl-4,5-dihydrofurans were obtained by manganese(III) acetate mediated radical cyclization of trifluoromethyl-1,3-dicarbonyl compounds (1a-c) with conjugated alkenes (2a-h). The reaction of 1,1,1-trifluoropentane-2,4-dione (1a) with propenylbenzene and 1,1-diphenyl-1-butene surprisingly yielded 3-(dihydrofuran-2(3H)-ylidene)-1,1,1-trifluoroacetones besides 3-trifluoroacetyl-4,5-dihydrofurans. 相似文献
999.
Effects of temperature and sodium carboxylate additives on mineralization of calcium oxalate in silica gel systems 总被引:5,自引:0,他引:5
Bernd Tieke 《中国科学B辑(英文版)》2004,47(4):311-319
Urolithiasis remains a major medical problem in China, especially in Guangdong Province in the southest of China[1]. A survey in Shenzhen city, the most southern city in China, showed the incidence of renal calculus was 4.87%, being 6.12% in the males and 4.07% in the females[2]. The prevalence of renal calculus has been more as the age advances and in the male population and so was in the less-educated population. The recurrence rate is more than 80%, with a moderate improvement by conventi… 相似文献
1000.