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61.
Summary Electrothermal (graphite furnace) atomic absorption spectrometry (ETAAS), as off-line detector for sedimentation field-flow
fractionation (SedFFF) is exploited in clay analysis.
Quantitation limits of coupled SedFFF-ETAAS for the determination of a submicron kaolin sample, considered a representative
model of natural water suspended particulate, are theoretically established and experimentally validated with reference to
Al and Si determination by ETAAS.
Complete sample recovery for a 4 μg injected kaolin sample was obtained by keeping adsorption in the SedFFF apparatus to a
minimum under control. The best experimental conditions, ensuring sample integrity, were low ionic strength (Na2CO3, 10−5 M), pH 8 and a Teflon covered accumulation wall. Several different runs, revealing the various experimental parameters affecting
quantitative recovery, are reported and the different physico-chemical processes affecting such recovery are discussed. The
advantages and drawbacks of SedFFF-ETAAS coupling compared with inductively coupled plasma-mass spectrometry (ICP-MS) technique
are also discussed. 相似文献
62.
In this work, SPLITT Fractionation (split flow thin cell) is used to sort hydrodynamically sedimented particles coming from the Sacca di Goro, a lagoon-like system close to the Po River delta (Italy). First the possibility of performing quantitative mass separations with a SPLITT cell apparatus was checked on a standard silica sample of known particle size distribution (PSD). Environmental sediment samples and relative SPLITT sub-fractions were subject to Inductive Coupled Plasma--Atomic Emission Spectroscopy (ICP-AES) characterization for the following elements: Al, Fe, Cd, Cr, Cu, Ni, Mn, Pb and Zn. The distribution of these metals by particle size fractions has been investigated. The accuracy of the entire separation procedure has been also evaluated. 相似文献
63.
64.
Sapp SA Elliott CM Contado C Caramori S Bignozzi CA 《Journal of the American Chemical Society》2002,124(37):11215-11222
A number of cobalt complexes of substituted polypyridine ligands were synthesized and investigated as possible alternatives to the volatile and corrosive iodide/triiodide redox couple commonly used as an electron-transfer mediator in dye-sensitized solar cells (DSSCs). The extinction coefficients in the visible spectrum are on the order of 10(2) M(-1) cm(-1) for the majority of these complexes, diminishing competition with the light-harvesting dye. Cyclic voltammetric studies revealed a dramatic surface dependence of the heterogeneous electron-transfer rate, which is surprisingly different for gold, carbon, and platinum electrodes. DSSCs were assembled using a mediator that consisted of a mixture of Co(II) and Co(III) complexes in a 10:1 ratio. DSSCs containing these mediators were used to characterize incident photon-to-current conversion efficiency and photoelectrochemical responses. The best performing of these mediators were identified and subjected to further study. As suggested by electrochemical results, gold and carbon are superior cathode materials to platinum, and no evidence of corrosion on any cathode material was observed. Addition of lithium salts to the mediator solution resulted in a dramatic improvement in cell performance. The observed Li(+) effect is explained in terms of the recombination of injected electrons in the photoanode with the oxidized mediator. The best mediator, based on tris(4,4'-di-tert-butyl-2,2'-dipyridyl)cobalt(II/III) perchlorate, resulted in DSSCs exhibiting efficiencies within 80% of that of a comparable iodide/triiodide-mediated DSSC. Due to the commercial availability of the ligand and the simplicity with which the complex can be made, this new mediator represents a nonvolatile, noncorrosive, and practical alternative as an efficient electron-transfer mediator in DSSCs. 相似文献
65.
Guido Zadel Catia Eisenbraun Gerd-Joachim Wolff Eberhard Breitmaier 《Angewandte Chemie (International ed. in English)》1994,33(4):454-456
Shortly after publication, E. Breitmaier, C. Eisenbraun, and G. J. Wolff declared their disassociation from this article owing to apparent manipulation of results by G. Zadel. Also see DOI: 10.1002/anie.199412011 , 10.1002/anie.199414571 , 10.1002/anie.199414581 , 10.1002/anie.199414591 . 相似文献
66.
Florio S Lorusso P Granito C Luisi R Troisi L 《The Journal of organic chemistry》2004,69(15):4961-4965
The vicarious nucleophilic substitution reaction of dichloromethyloxazoline 2 with nitrobenzene has been investigated. Treatment of 2 with t-BuOK followed by the addition of nitrobenzene leads to benzylic carbanions 4 or 9 depending upon the solvent used (DMSO, DMF, or THF). Subsequent treatment of 4 or 9 with aldehydes, in a Darzens-like reaction, furnishes very good yields of nitrophenyl oxazolinyloxiranes 8 and 11. 1,2-Dioxazolinyl-1,2-dinitrophenylethene 7 forms quantitatively when carbanion 4 is allowed to warm to room temperature in the absence of external electrophiles. 相似文献
67.
68.
Clementi C Ciocan V Vagnini M Doherty B Tabasso ML Conti C Brunetti BG Miliani C 《Analytical and bioanalytical chemistry》2011,401(6):1815-1826
The paper reports on the exploitation of an educated multi-technique analytical approach based on a wide non invasive step
followed by a focused micro-destructive step, aimed at the minimally invasive identification of the pigments decorating the
ceiling of the Gilded Vault of the Domus Aurea in Rome. The combination of elemental analysis with molecular characterization provided by X-ray fluorescence and UV–vis
spectroscopies, respectively, allowed for the in situ non-invasive identification of a remarkable number of pigments, namely
Egyptian blue, green earth, cinnabar, red ochre and an anthraquinonic lake. The study was completed with the Raman analysis
of two bulk samples, in particular, SERS measurements allowed for the speciation of the anthraquinonic pigment. Elemental
mapping by scanning electron microscopy-energy dispersive spectrometer combined with micro-fluorimetry on cross-section gave
an insight into both the distribution of different blend of pigments and on the nature of the inorganic support of the red
dye. 相似文献
69.
Caterina Temporini Gabriella Massolini Gabriella Marucci Catia Lambertucci Michela Buccioni Rosaria Volpini Enrica Calleri 《Analytical and bioanalytical chemistry》2013,405(2-3):837-845
A liquid chromatographic stationary phase containing immobilized membranes from cells expressing A2A adenosine receptor (A2AAR) is firstly described. Cellular membranes from CHO cells stably transfected with human A2AAR vector (A2A(+)) and from the same cell line transfected with the corresponding empty vector (A2A(?)) were entrapped on immobilized artificial membrane (IAM) support and packed into 6.6 mm I.D. glass columns to create A2A(+)-IAM and A2A(?)-IAM stationary phases. Frontal chromatography experiments on both A2A(+)-IAM and A2A(?)-IAM columns demonstrated the presence of a low specific interaction with the receptor. However, immobilized A2A retained its ability to specifically bind known ligands as demonstrated by the agreement of the calculated K d values with two different chromatographic protocols in comparison to previously reported data. In order to maximize the specific interaction, the same cellular membranes were immobilized on the inner surface of a silica capillary (40 cm?×?100 μm I.D.) by non-covalent interactions using the avidin–biotin coupling system to create two open tubular columns A2A(+)-OT and A2A(?)-OT. The open tubular system was characterized by ranking experiments for affinity studies in mixture useful for the selection of new potential candidates. Figure
Immobilized A2A receptor for Kd determination and ligand screening 相似文献
70.
Blo G Ceccarini A Conato C Contado C Fagioli F Fuoco R Pagnoni A Dondi F 《Analytical and bioanalytical chemistry》2006,384(4):922-930
Direct hyphenation of electrothermal atomic-absorption spectroscopy (ETAAS) to sedimentation field-flow fractionation (SdFFF)
has been developed to enable elemental characterization of submicron particles as a function of size. This hyphenation is
particularly suitable for characterizing colloidal particles of environmental interest, for example water-borne particles.
The interface is an automatic capillary injection device (CID) which enables direct introduction of large and variable volumes
of colloidal particle suspensions into a hot graphite furnace, thus preconcentrating the colloidal particles on the furnace
walls. The method was validated by determination of Fe in certified submicron Fe2O3. The procedure was set up by first optimizing the SdFFF fractionation under programmed field conditions, thus enabling optimum
fractionation of particle size. The ETAAS procedure was then tested to determine whether it could be used for direct analysis
of Fe2O3 slurries without the need for a mineralization step. CID coupled to ETAAS was subsequently exploited for its ability to enhance
the sensitivity, because of the increased injection volume. Statistical tests and data handling were conducted to prove the
suitability of the ETAAS-CID module. Finally, off-line and on-line ETAAS-CID-SdFFF hyphenation were investigated. These experiments
emphasized the advantages of the on-line coupling, because it enables synchronized sampling, enrichment, and elemental analysis
of the flowing eluate. The benefits of the proposed hyphenation are the high specificity of analytical detection, increased
sensitivity, reduction of analysis time, and minimum sample handling and contamination.
相似文献