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1.
Burguera JL Quintana IA Salager JL Burguera M Rondón C Carrero P Anton de Salager R Petit de Peña Y 《The Analyst》1999,124(4):593-599
An on-line time based injection system used in conjunction with cold vapor generation atomic absorption spectrometry and microwave-aided oxidation with potassium persulfate has been developed for the determination of the different mercury species in fish-eggs oil samples. A three-phase surfactant-oil-water emulsion produced an advantageous flow when a peristaltic pump was used to introduce the highly viscous sample into the system. The optimum proportion of the oil-water mixture ratio was 2:3 v/v with a Tween 20 surfactant concentration in the emulsion of 0.008% v/v. Inorganic mercury was determined after reduction with sodium borohydride while total mercury was determined after an oxidation step with persulfate prior to the reduction step to elemental mercury with the same reducing agent. The difference between total and inorganic mercury determined the organomercury content in samples. A linear calibration graph was obtained in the range 0.1-20 micrograms l-1 of Hg2+ by injecting 0.7 ml of samples. The detection limits based on 3 sigma of the blank signals were 0.11 and 0.12 microgram l-1 for total and inorganic mercury, respectively. The relative standard deviation of ten independent measurements were 2.8 and 2.2% for 10 micrograms l-1 and 8.8 and 9.0% for 0.1 microgram l-1 amounts of total and inorganic mercury, respectively. The recoveries of 0.3, 0.6 and 8 micrograms l-1 of inorganic and organic mercury added to fish-eggs oil samples ranged from 93.0 to 94.8% and from 100 to 106%, respectively. Good agreement with those values obtained for total mercury content in real samples by electrothermal atomic absorption spectrometry was also obtained, differences between mean values were < 7%. With the proposed procedure, 22 proteropterous catfish-eggs oil samples from the northwestern coast of Venezuela were measured; while the organic mercury lay in the range 2.0 and 3.3 micrograms l-1, inorganic mercury was not detected. 相似文献
2.
Darbost U Rager MN Petit S Jabin I Reinaud O 《Journal of the American Chemical Society》2005,127(23):8517-8525
The host-guest properties of calix[6]tren 1 have been evaluated. The receptor is based on a calix[6]arene that is covalently capped at the narrow rim by a tren unit. As a result, the system presents a concave hydrophobic cavity with, at its bottom, a grid-like nitrogenous core. Despite its well-defined cavity and opening to the outside at the large rim, 1 did not behave as a good receptor for neutral molecules in chloroform. However, it exhibited efficient endo-complexation of ammonium guests. By contrast, the per-protonated host, 1.4H(+), behaved as a remarkable receptor for small organic molecules. The complexation is driven by a strong charge-dipole interaction and hydrogen bonds between the polar guest and the tetracationic cap of the calixarene. Finally, coordination of Zn(2+) to the tren core led to the asymmetrization of calixarene cavity and to the strong but selective endo-binding of neutral ligands. This study emphasizes the efficiency of a receptor presenting a concave hydrophobic cavity that is polarized at its bottom. The resulting combination of charge-dipole, hydrogen bonding, CH-pi, and van der Waals interactions highly stabilizes the supramolecular architectures. Also, importantly, the tren cap allows the tuning of the polarization, offering either a basic (1), a highly charged and acidic (1.4H(+)), or a coordination (1.Zn(2+)) site. As a result, the system proved to be highly versatile, tunable, and interconvertible in solution by simple addition of protons, bases, or metal ions. 相似文献
3.
Pénicaud A Poulin P Derré A Anglaret E Petit P 《Journal of the American Chemical Society》2005,127(1):8-9
Upon reduction with alkali metals, single-wall carbon nanotubes (SWNTS) are shown to form polyelectrolyte salts that are soluble in polar organic solvents without any sonication, use of surfactants, or functionalization whatsoever, thus forming true thermodynamically stable solutions of naked SWNTs. 相似文献
4.
Petit C Bernardes-Génisson V Hoffmann P Souchard JP Labidalle S 《Chemical & pharmaceutical bulletin》2000,48(11):1634-1638
Five novel S-nitrosothiol compounds (6-10) derived from L-cysteine were generated in solution and their decomposition rate was followed by UV spectroscopy. In acetonitrile, compounds 9 and 10 were the most stable of this series with a half-life of 24 h. The final organic decomposition products of the five S-nitrosothiols were also analysed. Derivatives 8, 9, and 10, possessing a phenolic hydroxyl group, afforded an unexpected decomposition pathway, with nitration of aromatic ring occurring in non-aqueous media. A mechanism involving a phenoxy radical seems to be implicated. 相似文献
5.
A successful application of microwave irradiation, in which phthalocyanines were synthesized under solventless conditions from 1,2-phthalonitrile or phthalic anhydride and urea in the presence of metal templates is described. It was found that in comparison with conventional heating, the microwave process is a very useful alternative for cyclotetramerization processes because of reduction of the reaction time, better yield, and easy-to-perform procedure. 相似文献
6.
J. F. Chemin J. Roturier B. Saboya G. Y. Petit 《Journal of Radioanalytical and Nuclear Chemistry》1972,12(2):221-232
The use of direct observation of nuclear reactions (p,p′γ) is discussed. The main characteristics of this method are presented
and applied to the case of the miroanalysis of Si, S and Zn in GaSb. 相似文献
7.
Analysis of the structure of very large bacterial aggregates by small-angle multiple light scattering and confocal image analysis 总被引:1,自引:0,他引:1
Lambert S Moustier S Dussouillez P Barakat M Bottero JY Le Petit J Ginestet P 《Journal of colloid and interface science》2003,262(2):384-390
This work aims at developing a more accurate measurement of the physical parameters of fractal dimension and the size distribution of large fractal aggregates by small-angle light scattering. The theory of multiple scattering has been of particular interest in the case of fractal aggregates for which Rayleigh theory is no longer valid. The introduction of multiple scattering theory into the interpretation of scattering by large bacterial aggregates has been used to calculate the fractal dimension and size distribution. The fractal dimension is calculated from the form factor F(q) at large scattering angles. At large angles the fractal dimension can also be computed by considering only the influence of the very local environment on the optical contrast around a subunit. The fractal dimensions of E. coli strains flocculated with two different cationic polymers have been computed by two techniques: static light scattering and confocal image analysis. The fractal dimensions calculated with both techniques at different flocculation times are very similar: between 1.90 and 2.19. The comparison between two completely independent techniques confirms the theoretical approach of multiple scattering of large flocs using the Mie theory. Size distributions have been calculated from light-scattering data taking into account the linear independence of the structure factor S(q) relative to each size class and using the fractal dimension measured from F(q) in the large-angle range or from confocal image analysis. The results are very different from calculations made using hard-sphere particle models. The size distribution is displaced toward the larger sizes when multiple scattering is considered. Using this new approach to the analysis of very large fractal aggregates by static light multiple scattering, the fractal dimension and size distribution can be calculated using two independent parts of the scattering curve. 相似文献
8.
Some 3-aryloxy-1,2-epoxypropanes, interesting as potential synthons in β-adrenergic receptor antagonists preparation, were obtained in excellent yields (65-96% within 2-17 min) by microwave activation (monomode system) using solid-liquid solvent-free phase transfer catalysis (PTC). The best results for the O-alkylation of some phenols with epichlorohydrin were obtained using TBAB and NaOH/K2CO3 (1:4 mol/mol) as phase transfer catalyst and more acceptable basic system, respectively. These new procedure is compared with classical methods. Significant specific microwave effect (non-purely thermal) was evidenced in all cases. They were discussed in terms of reaction medium and mechanism, taking into account the variations in polarity of the systems. 相似文献
9.
Petit L Baraige F Bertheau Y Brunschwig P Diolez A Duhem K Duplan MN Fach P Kobilinsky A Lamart S Schattner A Martin P 《Journal of AOAC International》2005,88(2):654-664
The fate of DNA and protein transgenic sequences in products derived from animals fed transgenic crops has recently raised public interest. Sensitive molecular tests targeting the Bt176 genetic construct and the transgenic Cry1Ab protein were developed to determine whether plant sequences, especially transgenic sequences, are present in animal products. A protocol for total DNA extraction and purification from cow whole blood samples was first drawn up and assessed by spiking with known amounts of DNA from Bt176 maize. The limit of detection for transgenic sequences (35S promoter and Bt176-specific junction sequence) was determined by both the polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA) and the 5'-nuclease PCR assay. Four additional PCR systems were built to substantiate the results. The first detects a mono-copy maize-specific sequence (ADH promoter). Two others target multi-copy sequences from plant nucleus (26S rRNA gene) and chloroplast (psaB gene). The last one, used as a positive control, targets a mono-copy animal sequence (alpha(s1)-casein gene). Both methods detected a minimum spiking at 25 copies of Bt176 maize/mL in 10 mL whole blood samples. The sandwich ELISA kit used detected down to 1 ng transgenic Cry1Ab protein/mL spiked whole blood. 相似文献
10.
A simplified deconvolution procedure which can be used to remove the distortion, due to thermal lags, from calorimetric data is described and tested. The procedure is based on the state function theory. Noise in the deconvoluted data can be abated by smoothing the experimental data and by a careful choice of the data-sampling frequency. The method is adaptable to on-line processing by means of a microprocessor.
The authors gratefully acknowledge the assistance of Dr. J. Van Bokhoven, Chemisch Laboratorium TNO, Rijswyk, the Netherlands, during the experimental part of this work. 相似文献
Zusammenfassung Ein vereinfachtes Dekonvolutionsverfahren, das sich zur Behebung von infolge thermischer Lag-Erscheinungen auftretenden Zerrungen kalorimetrischer Daten eignet, wird beschrieben und getestet. Das Verfahren beruht auf der Theorie der Zustandsfunktion. Geräusche der Dekonvolutionsdaten können durch Ausgleichen der Versuchsdaten und durch sorgfältige Wahl der Datennahme-Frequenz gedämpft werden. Die Methode kann mittels eines Mikro-Verarbeiters zur on-line Verarbeitung eingesetzt werden.
Résumé Une procédure simplifiée de déconvolution qui peut être utilisée pour éliminer des courbes calorimétriques, la distorsion causée par l'inertie thermique du calorimètre, est décrite et testée. La procédure est basée sur la théorie des variables d'état. Le bruit de fond des courbes corrigées peut être diminué par le lissage des données expérimentales et par le choix d'une fréquence d'échantillonnage appropriée. La méthode peut être adaptée au traitement en ligne des données au moyen d'un microprocesseur.
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The authors gratefully acknowledge the assistance of Dr. J. Van Bokhoven, Chemisch Laboratorium TNO, Rijswyk, the Netherlands, during the experimental part of this work. 相似文献