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251.
In this work, the potentiality of asymmetrical flow field-flow fractionation (A4F) hyphenated to UV detector and multi-angle
light scattering (MALS) was investigated for accurately determining multi-walled carbon nanotube (MWCNT) length and its corresponding
dispersion state in aqueous medium. Fractionation key parameters were studied to obtain a method robust enough for heterogeneous
sample characterization. The main A4F conditions were 10−5 mL min−1 NH4NO3, elution flow of 1 mL min−1, and cross flow of 2 mL min−1. The recovery was found to be (94 ± 2)%. Online MALS analysis of eluted MWCNT suspension was performed to obtain length distribution.
The length measurements were performed with a 4% relative standard deviation, and the length values were shown to be in accordance
with expected ones. The capabilities of A4F-UV-MALS to size characterize various MWCNT samples and differentiate them according
to their manufacturing process were evaluated by monitoring ball-milled MWCNT and MWCNT dispersions. The corresponding length
distributions were found to be over 150–650 and 150–1,156 nm, respectively. A4F-UV-MALS was also used to evaluate MWCNT dispersion
state in aqueous medium according to the surfactant concentration and sonication energy involved in the preparation of the
dispersions. More especially, the presence or absence of aggregates, number and size of different populations, as well as
size distributions were determined. A sodium dodecyl sulfate concentration of 15 to 30 mmol L−1 and a sonication energy ranged over 20–30 kJ allow obtaining an optimal MWCNT dispersion. It is especially valuable for studying
nanomaterials and checking their manufacturing processes, size characterization being always of high importance. 相似文献
252.
Sarrazy V Garcia G MBakidi JP Morvan CL Bégaud-Grimaud G Granet R Sol V Krausz P 《Journal of photochemistry and photobiology. B, Biology》2011,103(3):201-206
Porphyrin-polyamine conjugates bearing two (cis or trans position) or four spermidine or spermine units were synthesized. We studied the photostability, the hydrophilic/lipophilic balance of porphyrin-polyamine derivatives and the production of singlet oxygen. All these compounds possess physicochemical features required for their use in PDT. Then, we investigated the photocytotoxic efficacy of these porphyrin-polyamine derivatives and the cell death pathway implicated. All compounds appear to be more efficient than Photofrin? to induce HaCat and MCF7 cell death, essentially by apoptosis. Collectively, these data show that porphyrin-polyamine conjugates could be promising phototherapeutic agents. 相似文献
253.
Two novel methods for determination of binding constants in the systems with borate and cyclodextrin complexation were developed. The methods enable to determine all binding parameters in these systems and even the binding constants of interaction of a neutral analyte with a neutral cyclodextrin. The first method is based on nonlinear fitting of experimental data and further evaluation of fitting parameters. The second method requires a multiple regression. The methods provide identical results with low experimental error. Only one set of measurements is required for both methods. Thus the binding parameters can be mutually compared. The binding parameters for neutral analytes ((R,R)-(+)-hydrobenzoin and (S,S)-(-)-hydrobenzoin) and neutral cyclodextrin (heptakis(2,6-di-O-methyl)-β-cyclodextrin) were evaluated and the effect of individual types of interaction was revealed. The interaction of the analytes with cyclodextrin governs the chiral recognition, while the complexation of analyte with borate is responsible for electromigration. Very low values of the binding constants of mixed analyte-cyclodextrin-borate complexes indicate that this type of complexation has negligible effect on enantioseparation. 相似文献
254.
Beaulieu MA Guérard KC Maertens G Sabot C Canesi S 《The Journal of organic chemistry》2011,76(22):9460-9471
An oxidative Prins-pinacol tandem process mediated by a hypervalent iodine reagent has been developed. This oxidative version of the famous tandem process fits within the concept of "aromatic ring umpolung" and allows the stereoselective transformation of simple phenols into highly elaborated spirocyclic dienone cores containing several quaternary carbon centers. The scope and the limitations of this process, including the study of its stereoselectivity, are described in this article. As a direct application of this stereoselective process, we describe the formal synthesis of (-)-platensimycin, an important antibiotic agent. 相似文献
255.
The accumulation of heavy metals in fish has been extensively studied and well documented. However, the research has been mainly focused on the muscle tissue, while the distribution patterns among other tissues, such as liver and gills, have been mostly neglected. Within the present study, the concentrations of Ag, Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Se, Sr, Zn and Li in the muscle, gills, liver and intestine of the sterlet (Acipenser ruthenus) from the Danube River have been assessed by using the inductively-coupled plasma optical spectrometry. The analysis has revealed a high degree of differential accumulation of the studied heavy metals and trace elements in the tissues of the Danube sterlet. Liver appeared to be the main heavy metal storage tissue, while the lowest levels of analyzed metals were found in muscles. Heavy metal concentrations in the muscle were at acceptable levels for human consumption, except partly for cadmium. We conclude that, in order to enable a more efficient control of contaminants in fish products, there is an apparent need to resolve the problem of lack of legal limits for many metals in European legislation. 相似文献
256.
Martin G Mansion F Houbart V Paquet P Rorive A Chiap P Crommen J Servais AC Fillet M 《Talanta》2011,84(2):280-286
The incidence of malignant melanona has increased over the past decades, particularly in Caucasian population. This disease presents defavourable prognosis in terms of survey, especially when detection occurs at the metastatic phase. Reliable analytical methods for biomarker determination are thus an interesting tool in pathology detection and follow-up. In this context, a method using SPE-LC-ESI-MS-MS for the determination of 5-S-cysteinyldopa (5-SCD) in human plasma was optimized. The presence of matrix effect was investigated in details while 5-SCD stability was studied according to FDA requirements for the validation of bioanalytical methods. Pre-study and in-study validations of the entire method were then successfully performed by applying the approach based on total measurement error and accuracy profiles over a concentration ranges from 1.6 to 200 ng/ml. Good results with respect to accuracy, trueness and precision were obtained. The maximum risk of observing future measurements falling outside the acceptance limits during routine analysis was also estimated. 相似文献
257.
A. Bojanowska-Czajka H. Nichipor P. Drzewicz B. Szostek A. Gałęzowska S. Męczyńska M. Kruszewski Z. Zimek G. Nałęcz-Jawecki M. Trojanowicz 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(2):303-314
The radiolytic degradation of widely used fungicide, carbendazim, in synthetic aqueous solutions and industrial wastewater
was investigated employing γ-irradiation. The effect of the absorbed dose, initial concentration and pH of irradiated solution
on the effectiveness of carbendazim decomposition were investigated. Decomposition of carbendazim in 100 μM concentration
in synthetic aqueous solutions required irradiation with 600 Gy dose. The aqueous solutions of carbendazim have been irradiated
in different conditions, where particular active radical species from water radiolysis predominate. The obtained data have
been compared with the kinetic modeling. The reversed-phase high-performance liquid chromatography was used for the determination
of carbendazim and its radiolytic decomposition products in irradiated solutions. The changes of toxicity of irradiated solutions
were examined with different test organisms and human leukemia cells. 相似文献
258.
Mendoza-Espinosa D Ung G Donnadieu B Bertrand G 《Chemical communications (Cambridge, England)》2011,47(38):10614-10616
The first examples of thiazol-5-ylidene complexes featuring group 9, 10 and 11 metal centers, have been prepared by deprotonation of a series of 2,3,4-triaryl-susbtituted thiazolium salts in the presence of the corresponding transition metal precursor. 相似文献
259.
Deffieux D Natangelo A Malik G Pouységu L Charris J Quideau S 《Chemical communications (Cambridge, England)》2011,47(5):1628-1630
The first total synthesis of a member of the C-glucosidic subclass of ellagitannins, 5-O-desgalloylepipunicacortein A, was accomplished by relying on a biomimetic aldol-type formation of its characteristic C-aryl glucosidic bond through the exploitation of the inherent chemical reactivity of a glucopyranosic hemiacetal precursor. 相似文献
260.