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排序方式: 共有550条查询结果,搜索用时 15 毫秒
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Agüera A Pérez Estrada LA Ferrer I Thurman EM Malato S Fernández-Alba AR 《Journal of mass spectrometry : JMS》2005,40(7):908-915
Exact mass capabilities of time-of-flight (TOF) mass spectrometry along with other mass spectrometric techniques have been evaluated to elucidate a complete range of dichlofenac phototransformation products. Photolysis experiments with diclofenac in water under direct solar irradiation were performed to characterise the main phototransformation products generated and to determine their stability. Photolysis experiments were performed in both demineralised water and reconstructed standard freshwater. Samples were extracted before analysis by solid phase extraction (SPE) with Oasis HLB and MAX cartridges. Separation and identification of the transformation products were accomplished by the combined use of gas chromatography-mass spectrometry (GC/MS) and liquid chromatography coupled with time-of-flight mass spectrometry (LC/TOFMS). Both techniques provided complementary information that enabled the identification of 13 phototransformation products. Six of them were identified by GC/MS through the structural information provided by the full scan mass spectra obtained under electron impact (EI) ionisation and the confirmation of the molecular mass provided by positive chemical ionisation (PCI) analyses. Accurate mass measurements obtained by LC/TOFMS provided the elucidation of seven polar transformation products. The low mass error observed (<2 ppm) enabled the assignment of highly probable empirical formulas as well as identification of a process dimerisation route. The photoproducts identified demonstrated that photolysis of diclofenac occurs by two main routes. One is the consequence of the initial photocyclisation of diclofenac into carbazole derivatives. The other route goes through the initial decarboxilation of diclofenac and further oxidation of the alkyl-chain, which are typical photolytic process reactions. The main photoproduct identified was 8-chloro-9H-carbazole-1yl-acetic acid. 相似文献
3.
A. Alba M. A. Aramendia V. Borau C. Jimenez J. M. Marinas 《Reaction Kinetics and Catalysis Letters》1984,25(1-2):45-50
The reduction of ,-unsaturated (olefin) carbonyl compounds of the type using a 0.75 wt.% Pd catalyst supported on SiO2–AlPO4 (8020 w/w) in a Parr reactor at low hydrogen pressure is reported. Selectivity in the reduction of the C=C bond is 100% in every case, and the nature of the groups A and B affects reaction rate, thus suggesting a 1,4-hydrogen addition mechanism.
, - () , , 0,75 . % Pd, SiO2–AlPO4 (8020 /), . C=C 100% , A B , 1,4- .相似文献
4.
5.
Le Faou JH Suomijärvi T Blumenfeld Y Piattelli P Agodi C Alamanos N Alba R Auger F Bellia G Chomaz P Coniglione R Del Zoppo A Finocchiaro P Frascaria N Gaardhoje JJ Garron JP Gillibert A Lamehi-Rachti M Liguori-Neto R Maiolino C Migneco E Russo G Roynette JC Santonocito D Sapienza P Scarpaci JA Smerzi A 《Physical review letters》1994,72(21):3321-3324
6.
Diacetylene-containing polyesters and polyurethanes were prepared by the reaction of m,m-butadiynylenedibenzyl alcohol with isophthaloyl chloride, sebacoyl chloride, hexamethylene diisocyanate and 2,4-tolylene diisocyanate. Their thermal behavior was studied by optical microscope and differential scanning calorimetry (DSC). The polyesters were crystalline. The polyurethane prepared from hexamethylene diisocyanate and polyphthalates crystallized on cooling from their melts. All turned a reddish brown color on heating at temperatures above 200°C, and prolonged heating led to a black resin, but thermal decomposition could not be avoided. Irradiation by γ-ray and UV light at room temperature deepened the color of the films, but the polymerization of the diacetylene groups was not appreciable. Simultaneous heating and irradiation was necessary to obtain transparent, amorphous, wine red colored films. 相似文献
7.
A. Segura Carretero C. Cruces Blanco R. Estrada Fernández A. Fernández Gutiérrez 《Analytical and bioanalytical chemistry》1998,360(5):605-608
A method for the determination of the fungicide thiabendazole (TBZ) by micellar-stabilized room-temperature phosphorescence is described. It does not require any separation step and allows the direct determination of the fungicide in canned pineapple samples. The effect of various experimental conditions is discussed in detail. The analytical curve of thiabendazole gives a linear dynamic range of 23.8–500.0 ng mL–1 and a detection limit of 23.8 ng mL–1. Recoveries of 103.9 and 89.2% for syrup and canned pineapple pulp, respectively, were obtained for 250 ng mL–1 thiabendazole. 相似文献
8.
A. L. O. Damasceno A. Iwahara M. A. L. Silva J. J. S. Estrada 《Journal of Radioanalytical and Nuclear Chemistry》2006,269(2):317-323
Summary The radionuclide 192Ir has been increasingly used as a brachytherapy source and manufactured in different geometry forms (thin wires, hairpins,
needles or point sources). A procedure for the characterization of the activity content of 192Ir wire sources was developed in order to establish the secondary standard activity measurement system based on the ionization
chamber set up at Brazilian National Laboratory for Ionizing Radiation Metrology (LNMRI). Firstly, the ion current of the
ionization chamber is measured and, subsequently, the activity is determined in a destructive analysis. This procedure enables
obtaining the calibration factor for wire sources that can be used for further activity determination of similar sources in
a non-destructive analysis. Accurate activity determination is needed for dosimetric measurements and for helping the manufacturers
to improve its quality control programs. 相似文献
9.
Alba Díaz-Rodríguez 《Tetrahedron letters》2005,46(35):5835-5838
Regioselective syntheses of several O-crotonyl 2′-deoxynucleoside derivatives have been efficiently achieved using a biocatalytic methodology. While Candida antarctica lipase B (CAL-B) afforded the 5′-O-acylated compounds, immobilized lipase from Pseudomonas cepacia (PSL-C) provided the 3′-O-crotonylated analogs. Since classical chemical approaches did not work appropriately due to side isomerization reactions, a mixture of both lipases was used to achieve a useful synthetic route toward diacylated nucleosides. 相似文献
10.
Large-scale ultrasonic cleaning system: Design of a multi-transducer device for boat cleaning (20kHz) 总被引:1,自引:0,他引:1
Mazue G Viennet R Hihn JY Carpentier L Devidal P Albaïna I 《Ultrasonics sonochemistry》2011,18(4):895-900
The present study is part of a global project which consists in the development of an automatic cleaning station for immersed boats (cockle, ninepin, etc.) in a self-service mode, associating an innovative ultrasonic device for cleaning with a specific water treatment. The originality of the process is that cleaning is performed by three transducers operating simultaneously at low frequency and moving along the surface, thanks to programmable logic controllers, and that it includes a suction to collect the dirt removed. Therefore, the time required for boat maintenance is shortened, ensuring high quality cleaning without the need for dry docks and avoiding additional pollution in the harbor areas. One of the key points was the evaluation of washing efficiency, as it is really hard to give a quantitative estimation of the dirt removed. To obtain the first design laws, feasibility tests have been carried out on dirty cockle samples and on real boat hulls with a laboratory ultrasonic device. The influence of a large number of parameters was tested such as transducer-probe distance, displacement speed and transmitted power. The obtained data allowed us to design an optimized cleaning device combining high efficiency and speed. 相似文献