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971.
A simple and efficient hollow fiber liquid‐phase microextraction (HF‐LPME) technique in conjunction with high‐performance liquid chromatography is presented for extraction and quantitative determination of aristolochic acid I in human urine samples. Several parameters influencing the efficiency of HF‐LPME were investigated and optimized, including extraction solvent, stirring rate, extraction time, pH of donor phase and acceptor phase. Excellent sample clean‐up was observed and good linearity with coefficient of 0.9999 was obtained in the range of 15.4–960 µg/L. This method provided a 230‐fold enrichment factor and good repeatability with relative standard deviations (RSD) lower than 6.0%. The limit of detection value for the analyte in urine sample was 0.01 µg/L at a signal‐to‐noise ratio of 3. The extraction recovery from urine samples was 61.8% with an RSD of 9.71%. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
972.
Alexander Björling Elisabet Ahlberg Juan M. Feliu 《Electrochemistry communications》2010,12(3):359-361
Electrochemical oxygen adsorption/desorption below monolayer level leads to a disordering of platinum single-crystal surfaces vicinal to the (1 1 1) plane. The kinetics can be described by means of a consecutive reaction from (1 1 1)-terrace sites to (1 1 0)-defect sites, in which (1 0 0)-defects act as intermediates. The first oxidation of the electrode reflects independent contributions from terrace and step sites, the latter being structure sensitive. Oxygen adsorption charges amount to a mean value of one electron per step site. 相似文献
973.
Garbiñe Álvarez Francisco Alcaide Oscar Miguel Laura Calvillo María Jesús Lázaro Jacob J. Quintana Juan Carlos Calderón Elena Pastor 《Journal of Solid State Electrochemistry》2010,14(6):1027-1034
This paper presents the behavior of ordered mesoporous carbon (OMC)-supported catalysts as anodes for direct methanol fuel
cells (DMFC), fed with an aqueous methanol solution. OMC samples were prepared by the nanocasting method from a polymerized
furan resin using mesoporous silica as a template. Pt and PtRu nanoparticles were supported on OMC with high dispersion, the
particle size being 2.4 nm at PtRu loading of 15 wt.%. The resulting catalysts were analyzed using carbon monoxide stripping
voltammetry, cyclic voltammetry, and chronoamperometry in three-electrode experiments and recording cell voltage vs. current
density curves in practical DMFC. It was found that PtRu-catalyzed technical electrodes exhibited good activity towards methanol
electrooxidation in half-cell experiments under fuel-cell-relevant conditions. Specifically, Pt85Ru15/OMC catalyst showed the highest catalytic enhancement compared to Pt/OMC for the steady-state electrooxidation of methanol
at 60 °C and 0.5 V, by a factor of 22 in 2-M MeOH solution. DMFC single cells yielded an open-circuit voltage of 0.625 V at
60 °C. Polarization curves indicate that DMFC with OMC-supported Pt85Ru15 catalyst at the anode exhibited the best performance. 相似文献
974.
975.
976.
Molecularly imprinted microspheres (MIMs) were prepared by suspension polymerization for the binding and recognition of dibutyl phthalate (DBP). DBP was used as the template molecule, methacrylic acid as the functional monomer, ethylene dimethacrylate (EDMA) as the linking agent, PVA as the dispersing agent, and Span 60 as the surfactant. The MIMs were characterized with electron microscope scanning and rebinding experiments. The Scatchard plot revealed that the template‐polymer system has a two‐site binding behavior with dissociation constants of 4.05 and 0.515 mmol/L. The MIMs exhibited the highest selective rebinding to DBP at 736.85 μg/g. The recoveries of the MIM‐SPE column for DBP extraction was 94.75–101.9% with the RSD of 1.5–7.3%, indicating the feasibility of the prepared MIMs for DBP extraction. Finally, the method developed was used to analyze the trace levels of phthalate in aqueous environment samples. 相似文献
977.
Simultaneous determination of seven alkaloids in Phellodendron chinense Schneid by high-performance liquid chromatography 总被引:1,自引:0,他引:1
By optimizing the extraction, separation, and analytical conditions, a reliable and accurate HPLC method coupled with a photodiode array detector was developed for simultaneous detection and quantification of seven alkaloids, i.e., (-)-(R)-platydesmin, noroxyhydrastinine, berberine, skimmianine, canthin-6-one, chilenine, and pteleine in "huangbo" (the bark of Phellodendron chinense), a commonly used herb in Traditional Chinese Medicine. The optimal condition for separation was achieved on a reversed-phase Cis column with a stepwise mobile phase gradient prepared from 0.1% phosphoric acid and acetonitrile. For all the alkaloids, a good linear regression relationship (r > 0.9997) was obtained between the peak area and concentration at the range of 0.5-700 microg/mL. The LODs and LOQs for the analytes ranged from 0.07 to 0.28 microg/mL and from 0.28 to 1.12 microg/mL, respectively. The optimized method was applied to the determination of alkaloids in several P. chinense samples, and found to be feasible and reliable. This method and quantitative results can provide scientific and technical bases for setting up QC standards to assure the safety and quality of P. chinense bark raw material, as well as for proprietary Chinese medicine products containing P. chinense bark. 相似文献
978.
Juan Peng Lily Zu Weihai Fang Lingyun Huang Yaru Wang Dacheng He 《Journal of mass spectrometry : JMS》2010,45(6):627-634
An understanding of the dissociation of penetratin is important for improving its metabolic stability and cargo‐delivery efficiency. In this study, we describe the selective cleavage of the K15–K16 amide bond of penetratin under the low‐energy collision‐induced dissociation condition in mass spectrometry. A variety of penetratin substitutes have been studied in which key basic amino acids have been substituted within the sequence. The calculated structure indicates that an α‐helix structure prevents the fragmentation of the central peptide domain and the side chain of lysine is involved in the proton translocation process. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
979.
Mata S Cortijo V Caminati W Alonso JL Sanz ME López JC Blanco S 《The journal of physical chemistry. A》2010,114(43):11393-11398
The Fourier transform microwave spectra of the hydrated forms of the tautomeric pair 2-pyridinone/2-hydroxypyridine (2PO/2HP) have been investigated in a supersonic expansion. Three hydrated species, 2PO-H?O, 2HP-H?O, and 2PO-(H?O)?, have been observed in the rotational spectrum. Each molecular complex was confidently identified by the features of the 1?N quadrupole hyperfine structure of the rotational transitions. The presence of water affects the tautomeric equilibrium -N═C(OH)- ? -NH-C(═O)-, which is shifted to the enol form for the bare molecules 2PO/2HP but to the keto tautomer for the hydrated forms. 相似文献
980.
Increase of pH induced by Cu(2+)-catalyzed Fenton reaction promoted ring-opening of triazole-linked fluorescein lactone, which enabled selective "turn-on" fluorescent detection of Cu(2+), along with ultralow naked-eye detection limit down to 200 nM. 相似文献