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11.
A totally automated and reliable high-performance liquid chromatographic method is described for the routine determination of free catecholamines (norepinephrine, epinephrine and dopamine) in urine. The catecholamines were isolated from urine samples using small alumina columns. A standard automated method for pH adjustment of urine before the extraction step has been developed. The extraction was performed on an ASPEC (Automatic Sample Preparation with Extraction Columns, Gilson). The eluate was collected in a separate tube and then automatically injected into the chromatographic column. The catecholamines were separated by reversed-phase ion-pair liquid chromatography and quantified by fluorescence detection. No manual intervention was required during the extraction and separation procedure. One sample may be run every 15 min, ca. 96 samples in 24 h. Analytical recoveries for all three catecholamines are 63-87%, and the detection limits are 0.01, 0.01, and 0.03 microM for norepinephrine, epinephrine and dopamine, respectively, which is highly satisfactory for urine. Day-to-day coefficients of variation were less than 10%. 相似文献
12.
Different ratios of phosphomolybdic acid PMA supported on silica gel (1–30 wt%) and promoted with alkali metal hydroxide have been prepared by an impregnation method and calcinated at 350 °C for 4 h. The catalysts were characterized by thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffraction, FT-IR spectroscopy and N2 adsorption measurements. The surface acidity and basicity of the catalysts were determined by adsorption of pyridine and the dehydration–dehydrogenation of 2-propanol. The gas-phase esterification of acetic acid by ethanol was carried out in a conventional flow bed reactor. The results clearly revealed that among the PMA loading, the use of 10 wt% catalyst showed maximum yield of ethyl acetate. This catalyst also improved on addition of Na or K-hydroxide. These results were correlated with the structure and the acid–base properties of the prepared catalysts. 相似文献
13.
Nathaniel L SegravesSuzette Lopez Tyler A JohnsonSadri A Said Xiong FuFrancis J Schmitz Halina PietraszkiewiczFrederick A Valeriote Phillip Crews 《Tetrahedron letters》2003,44(17):3471-3475
The structural variations and bioactivity properties of the alkaloids in the fascaplysin (1) and the reticulatine (3) families were examined. Four organisms were analyzed consisting of two collections of the sponge Fascaplysinopsis reticulata and two collections of the tunicate Didemnum sp. Reported are the isolation of three new compounds: 3-bromofascaplysin (2), 14-bromoreticulatine (4), and 14-bromoreticulatate (6) along with reticulatate (5) previously known as a semi-synthetic product of 1. Compounds 1 and 5 showed selectivity in a cell based cytotoxicity assay. 相似文献
14.
Said M. Bayomi 《中国化学会会志》1992,39(1):101-104
A convenient route is reported for the synthesis of fused pyrrolo[2,3-d][1,3]oxazine and pyrrolo[2,3-d]-pyrimidine derivatives from 2-amino-1-benzyl-3-t-butoxycarbonyl]-4,5-dimethylpyrrole. 相似文献
15.
Ahmed A. Abdel-Khalek Said M. Sayyah Fadia F. Abdel-Hameed 《Transition Metal Chemistry》1994,19(1):108-110
A novel chromium(III) complex of tetraoxalylurea was prepared. In aqueous solutions, [CrIII(H2L)(H2O)]+ (H2L = diprotonated tetraoxalylurea) is oxidized by IO
4
–
according to the rate law
相似文献
16.
17.
Emulsion liquid membranes (ELM) with di-2-ethylhexylphosphoric acid in n-alkane, and dipicrylamine and cobalt(III) dicarbollide in nitrobenzene stabilized in double emulsions by SPAN 80/85 surfactant were used for preconcentration of radioactive fission products (137Cs,90Sr,139Ce, and152Eu) from slightly acidic nitrate solutions. The efficiency of sulfuric, phosphotungstic and silicotungstic acids as stripping agents, and picric acid as the bulky anion additive was investigated. A group separation of the fission products is possible by the ELM technique and can be considered for their removal from waste water solutions. 相似文献
18.
The influence of the presence of trimethylsilyl and triphenylsilyl groups in substituents of anthraquinone on the properties of anthraquinone vat, acid, and dispersion dyes was investigated. 相似文献
19.
The activity of four bismuth(III) derivatives when employed as Friedel-Crafts catalysts for the acylation of aromatics was found to increase dramatically when dissolved in ionic liquids. Solutions of bismuth oxide or triflate in [emim][NTf(2)] and [bmim][NTf(2)] are the most efficient catalytic systems, with catalyst loading as low as 1% leading to clean, high-yielding acylation of a variety of benzene derivatives. These improved Friedel-Crafts catalytic systems can also be efficiently recycled as opposed to traditional systems. [reaction: see text] 相似文献
20.
C. Marhag H. Said P. Satre C. Favotto J. Rogez 《Journal of Thermal Analysis and Calorimetry》2003,74(1):275-285
Study of solid-liquid phase diagram of LiPO3-Pb(PO3)2 binary system, in certain calcination conditions, shows the existence of several metastable phasis. When heated at a temperature
of 723 K the binary mixtures lead uncompletely to a defined compound Pb2Li(PO3). On heating these ternary solid mixtures, three eutectic reactions have been observed: LiPO3+Pb(PO3)2→Liquid at a temperature of 793 K(1) LiPO3+Pb2Li(PO3)5→Liquid at a temperature of 843 K (2) Pb2Li(PO3)5+Pb(PO3)2→Liquid at a temperature of 891 K (3) The metastable liquid phase appears in the system at temperature of 793 K. DTA experiments
performed on the binary LiPO3-Pb(PO3)2 mixtures, show a superposition of two diagrams. The first one is metastable and the second represents the stable equilibrium
phase diagram. Measurements of liquid enthalpy of binary LiPO3-Pb(PO3)2 system at temperature of 979.65 K were reported. The corresponding values were very small and so the binary system can be
considered as athermal. Assuming an ideal behaviour, the liquidus curves in the metastable diagram were calculated and the
eutectic reaction (LiPO3-Pb(PO3)2→Liquid) was confirmed at 793 K.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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