排序方式: 共有106条查询结果,搜索用时 140 毫秒
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Sofie Cambré Wim Wenseleers Dr. Jelena Čulin Dr. Sabine Van Doorslaer Prof. Dr. Antonio Fonseca Dr. Janos B. Nagy Prof. Dr. Etienne Goovaerts Prof. Dr. 《Chemphyschem》2008,9(13):1930-1941
Single‐walled carbon nanotubes (SWCNTs) are noncovalently functionalised with octaethylporphyrins (OEPs) and the resulting nanohybrids are isolated from the free OEPs. Electron paramagnetic resonance (EPR) spectroscopy of cobalt(II)OEP, adsorbed on the nanotube walls by π–π‐stacking, demonstrates that the CNTs act as electron acceptors. EPR is shown to be very effective in resolving the different interactions for metallic and semiconducting tubes. Moreover, molecular oxygen is shown to bind selectively to nanohybrids with semiconducting tubes. Water solubilisation of the porphyrin/CNT nanohybrids using bile salts, after applying a thorough washing procedure, yields solutions in which at least 99 % of the porphyrins are interacting with the CNTs. Due to this purification, we observe, for the first time, the isolated absorption spectrum of the interacting porphyrins, which is strongly red‐shifted compared to the free porphyrin absorption. In addition a quasi‐complete quenching of the porphyrin fluorescence is also observed. 相似文献
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Chitneni SK Serdons K Evens N Fonge H Celen S Deroose CM Debyser Z Mortelmans L Verbruggen AM Bormans GM 《Journal of chromatography. A》2008,1189(1-2):323-331
This study describes an efficient method using on-line solid-phase extraction (SPE) (Oasis HLB) for preparative HPLC purification of short-lived radiotracers for positron emission tomography (PET) and for HPLC analysis of radiotracers and their metabolites in cell homogenates, plasma and urine samples. The radiochemical purity of tracers (fluorine-18 labeled) purified using this method (Oasis column) was >99% compared to 90% when no Oasis column was used. Radiometabolites of several fluorine-18 and carbon-11-labeled tracers and one technetium-99m tracer were quantified in cell homogenates, plasma and urine samples. Samples were analyzed using Oasis column and analytical HPLC system without prior precipitation of proteins or removal of other biological matrices. The metabolites observed for the evaluated tracers were all polar relative to the unchanged tracer. The extraction repeatability was found to be good (RSD 2.2%) and recoveries of Oasis column/HPLC-injected radioactivity (plasma) were found to be high (mean recovery >91%). The same Oasis column was used for several times without back pressure build-up or decrease of the HPLC separation characteristics. 相似文献
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We consider a latency problem with a profit pi for each client. When serving a client, a revenue of pi−t is collected. The goal is to find routes for the servers such that total collected revenue is maximized. We study the complexity of different variants of this problem on the line. 相似文献
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Sofie Hultgren Niklas Larsson Bo F. Nilsson Jan Åke Jönsson 《Analytical and bioanalytical chemistry》2009,393(3):929-937
A two-phase hollow-fiber (HF) liquid-phase microextraction (LPME) method was developed for determination of a quaternary ammonium
compound surfactant, dicocodimethylammonium chloride, in aqueous samples. The porous HF was fixed on a metal rod support and
was impregnated with approximately 6.6 μL of organic extractant, which was immobilized in the HF pores. Surfactant extraction
was facilitated by addition of carboxylic acid to the sample forming neutral ion pairs with the quaternary ammonium compound.
After extraction, the analyte was transferred from the organic extractant in the fiber pores by dissolving the 1-octanol into
100 μL methanol. The methanol extract was analyzed by liquid chromatography–mass spectrometry. The method was optimized (with
optimized parameters in brackets) with regard to type of organic extractant (1-octanol), fiber length (2 cm), choice and concentration
of anionic carrier (600 μg L−1 octanoate), procedure of transfer to methanol (15-min sonication), sample volume (250 mL), extraction time (17 h), pH (10),
and ionic strength (50 mM carbonate). Aspects influencing repeatability in LPME of (quaternary ammonium) surfactants are discussed.
The enrichment factor achieved in 250-mL carbonate buffer was around 400. Due to matrix effects, the enrichment factors achieved
when industrial process water was analyzed were 120 or about 30% of that in carbonate buffer. Detection limits of 0.3 μg L−1 in carbonate buffer and 0.9 μg L−1 in industrial process water were obtained. If the studied compound is seen as a model substance representing quaternary dialkylated
dimethylated ammonium surfactants in general, the developed method may be applied to other quaternary ammonium surfactants. 相似文献
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Nathalie Scheers Thomas Andlid Marie Alminger Ann‐Sofie Sandberg 《Electroanalysis》2010,22(10):1090-1096
The objective was to investigate interactions between iron and food chelators in an aqueous environment. The net complexation were investigated by DPASV in a NaClO4 electrolyte using a platinum electrode. The experimental conditions were simulating the environment of the human duodenum. The results indicated a net coordination affinity between Fe2+ and the organic acids in the following order; ascorbic acid≈phytate>pyruvate>lactate>acetate. For Fe3+ net complexation, the stability was in the order of lactate>phytate>pyruvate>acetate>citrate. In conclusion, DPASV in conjunction with a platinum electrode is suitable for studies in aqueous systems where the net complexation of metal is important. 相似文献
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