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991.
Matthias Tacke Lorcan T. Allen William M. Gallagher Oscar Mendoza Franz-Josef K. Rehmann 《Journal of organometallic chemistry》2004,689(13):2242-2249
Starting from 6-(p−N,N-dimethylanilinyl)fulvene (1a) or 6-(pentamethylphenyl)fulvene (1b) [1,2-di(cyclopentadienyl)-1,2-di(p−N,N-dimethylaminophenyl)ethanediyl] titanium dichloride (2a) and [1,2-di(cyclopentadienyl)-1,2-bis(pentamethylphenyl)ethanediyl] titanium dichloride (2b) and their corresponding dithiocyanato complexes (3a, 3b) were synthesized. Titanocene 2b did not show a cytotoxic effect, but when 2a was tested against pig kidney carcinoma cells (LLC-PK) or human ovarian carcinoma cells (A2780/cp70) inhibitory concentrations (IC50) of 2.7 × 10−4 and 1.9 × 10−4 M, respectively, were observed. 相似文献
992.
An on-line coupled continuous flow liquid membrane extraction (CFLME) and C18 precolumn system was developed for sample preconcentration in liquid chromatography determination. After preconcentration by CFLME, which is based on the combination of continuous flow liquid–liquid extraction and supported liquid membrane, bisphenol A (BPA) was enriched in 960 μl of 1 mol l−1 NaOH used as acceptor. This acceptor was on-line neutralized and transported onto the C18 precolumn where analytes were absorbed and focused. Then the focused analytes were injected onto a C18 analytical column for separation and detected at 220 nm with a diode array detector. CFLME related parameters such as flow rates, pH of donor and acceptor, and enrichment time were optimized. The proposed method presents a detection limit of 0.03 μg l−1 (S/N=3) when 60 ml samples was enriched with an enrichment time of 30 min. Compared with C18 based column-switching procedure, this proposed procedure presents similar sample throughput and lower detection limits. The proposed method was successfully applied to determine BPA in tap water, river water, and municipal sewage effluent samples. 相似文献
993.
Improvement of cyclosporin A determination in whole blood by reversed-phase high-performance liquid chromatography 总被引:1,自引:0,他引:1
A chromatographic method was developed for the determination of cyclosporin A in human whole blood using reversed-phase HPLC at room temperature. Most previous reports carried out this liquid chromatographic separation at temperatures above 70 degrees C. The present procedure greatly improves the detection limit by controlling peak broadening effects, as well as the lifetime of the column at room temperature. Under optimal conditions and using ketoconazole as an internal standard, the calibration graph was linear in the range of 16-1000 microg/L with a relative standard deviation of 3.72% at 150 microg/L and 2.45% at 300 microg/L (n = 11) of cyclosporin A. The detection limit was of 5.0 microg/L cyclosporin A. By this procedure, cyclosporin A pharmacokinetic parameters in healthy Chinese subjects were studied. The developed method could be applied to the quantification of cyclosporin A in human blood samples and allows the study of its pharmacokinetics in routine laboratories. 相似文献
994.
Sabry K. Mohamed 《Analytica chimica acta》2006,562(2):204-209
A poly(vinyl chloride)-based membrane of 2,9-dimethyl-4,11-diphenyl-1,5,8,12-tetraazacyclotetradeca-1,4,8,11-tetraene (DDTCT) with sodium tetraphenyl borate (STB) as an anion excluder and dibutyl phthalate (DBP), dibutyl butylphosphonate (DBBP), tris(2-ethylhexyl) phosphate (TEP) and tributyl phosphate (TBP) as plasticizing solvent mediators was prepared and investigated as a Ga(III)-selective electrode. The best performance was observed with the membrane having the ligand-PVC-DBP-STB composition 1:4:1:1, which worked well over a wide concentration range (1.45 × 10−6 to 0.1 mol L−1) with a Nernstian slope of 28.7 mV per decade of activity between pH 4.0 and 10.0. This electrode showed a fast response time of 12 s and was used over a period of 100 days with good reproducibility (s = 0.3 mV). The selectivity coefficients for monovalent, divalent and trivalent cations indicate excellent selectivity for Ga(III) ions over a large number of cations. Anions such as Cl− and SO42− do not interfere and the electrode also works satisfactorily in partially water-alcohol medium. The practical utility of the membrane sensor has also been observed in solutions contaminated with detergents, i.e., cetyltrimethylammonium bromide and sodium dodecyl sulfate and used for the determination of gallium in nickel alloy, fly-ash and biological samples. 相似文献
995.
Syndiotactic specific polymerization of styrene has been investigated by ~(13)C NMR analysis and isotopic laelling methods. The value of the activation energy involved in the steric control has been determined. Some information of the number of the active sites and on the life of the catalysts is reported. 相似文献
996.
Complete 1H and 13C NMR assignments of aurasperone A and fonsecinone A, two bis-naphthopyrones produced by Aspergillus aculeatus 总被引:1,自引:0,他引:1
Campos FR Barison A Daolio C Ferreira AG Rodrigues-Fo E 《Magnetic resonance in chemistry : MRC》2005,43(11):962-965
Complete assignments of 1H and 13C NMR chemical shifts of the polyketides aurasperone A and fonsecinone A were made by means of nuclear Overhauser enhancement and heteronuclear NMR correlation experiments. These compounds were isolated for the first time from Aspergillus aculeatus, an endophytic fungus obtained from leaves of Melia azedarach(Meliaceae). 相似文献
997.
The post-translational modifications of the 96 kDa protein dynamin A from Dictyostelium discoideum were analyzed using Q-TOF mass spectrometry. The accurate molecular mass of the intact protein revealed a covalent modification causing an additional mass of 42 Da. The modification could be identified as N-terminal acetylation by tandem mass spectrometry. Extracted ion chromatograms for the a(1) and b(1) ion of the tryptic T1 peptide were used to detect the acetylated peptide within 54 nanoelectrospray ionization tandem mass spectra. Owing to the accurate molecular mass of the intact protein, additional covalent modifications could be excluded. In addition to the covalent modification, the domain structure of dynamin A was determined by applying a combination of limited proteolysis, sodium dodecylsulfate polyacrylamide gel electrophoresis, automated tandem mass spectrometry and protein database searching. 相似文献
998.
999.
Ochratoxin A (OTA) is a secondary fungal metabolite produced by several moulds, mainly by Aspergillus ochraceus, A. carbonarius, A. niger and by Penicillium verrucosum. The present work shows the results of comparative studies using different procedures for the analysis of OTA in maize bread samples. The studied analytical methods involved extraction with different volumes of PBS/methanol, different extraction apparatus, and clean-up through immunoaffinity columns. The separation and identification were carried out by high-performance liquid chromatography with fluorescence detection. The optimized method for analysis of OTA in maize bread involved extraction with PBS:methanol (50:50), and clean-up with IAC column. The limit of quantification was 0.033 ng g−1. Recoveries ranged from 87% to 102% for fortifications at 2.000 and 0.500 ng g−1, respectively, within-day R.S.D. of 1.4% and 4.7%. The proposed method was applied to 15 samples and the presence of OTA was found in nine samples at concentrations ranging from nd to 2.650 ng g−1. 相似文献
1000.
The properties of porphyrinogen as a new chromogenic reagent were examined. 5,10,15,20-Tetrahydro-tetraphenylporphyrinogen (TPPN) is changed to 5,10,15,20-tetraphenylporphine (TPP) by the oxidative reaction involving six electrons, and its formation of the porphine ring significantly increased the absorbance in the Soret band.The horseradish peroxidase (HRP) accelerated the oxidative reaction as a catalyst and the increment of absorbance depended upon the increase in the concentration of HRP. The reaction proceeded in the presence of dissolved oxygen and in the neighborhood of pH 7. Based on these findings, a chemical analysis by catalytic action using HRP was developed.In the procedure for this determination, the difference in absorbance at 419 nm (ΔA419=As−Ab, where As and Ab are the absorbances of the sample solution containing HRP and the blank solution without HRP after 30 min, respectively), was measured. The determination range of HRP, which was obtained from the ΔA419—HRP concentration curve, was 0.05-1.0 mg/l. The relative standard deviation in the median of the calibration curve was 3.19% (seven determinations), and the detection limit (S/N=3) was 29 ng/l. Furthermore, when the proposed method was applied to the enzyme immunoassay, bisphenol A (BPA) was selectively and sensitivity determined. 相似文献