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121.
Di Michele A Brinchi L Di Profio P Germani R Savelli G Onori G 《Journal of colloid and interface science》2011,358(1):160-166
The critical micelle concentration (cmc) and ionisation degree (α), of micelles of cetyltrimethylammonium bromide (CTABr), cetyltrimethylammonium chloride (CTACl), cetyltripropylammonium bromide (CTPABr) and cetyltripropylammonium chloride (CTPACl) have been measured over a narrow temperature range at 2 degree intervals using electrical conductivity. CTPACl and CTPABr are very soluble in water and were measured in the temperature range 275.15-323.15K. The Krafft temperatures for CTABr and for CTACl are 293.15K and 284.15K, respectively and established a lower temperature limit for our studies on these two surfactants. The cmc vs temperature curves have a smooth minimum near room temperature and α linearly increases with temperature. The changes of cmc and α with temperature are smaller than those associated with the modification of head group size or counterion nature. Using these results, basic thermodynamic quantities associated with the phenomena of micellization have been evaluated. Thermodynamic properties of the surfactant solutions were discussed in terms of temperature dependence of the free energy, enthalpy and entropy of micellization. A close similarity between the effects of change in temperature on protein folding and micellization process appears from the data. 相似文献
122.
Mauro Epifani Elisabetta Comini Guido Faglia Jordi Arbiol Teresa Andreu Giovanni Pace Pietro Siciliano Joan R. Morante 《Journal of Sol-Gel Science and Technology》2011,60(3):254-259
A titanium chloromethoxide solution was prepared by reacting TiCl4 with methanol, followed by water addition. The starting solutions were characterized by Fourier Transform Infrared (FTIR) spectroscopy, evidencing that the in situ generated water results in early hydrolysis of the chloroalkoxide. The solution was reacted with molten dodecylamine at room temperature, obtaining a white slurry of amorphous titania nanoparticles. Stable, redispersible TiO2 nanocrystals could be prepared by subsequent solvothermal treatment in oleic acid at 250???C. The use of oleic acid was essential for obtaining crystalline structures, while other surfactants prevented crystallization. The nanocrystals were characterized by X-ray Diffraction and Transmission Electron Microscopy, confirming the formation of anatase TiO2 nanocrystals with a mean size of 3.3?nm. The TiO2 nanocrystals were used for fabricating gas-sensing devices, which were tested towards ethanol vapors. The initial small size of the nanocrystals, and the limited size growth during the high-temperature sensor operation, result in remarkable sensing performances if compared with bulk titania sensors. 相似文献
123.
Roberta Seraglia Giovanni Sartore Raffaella Marin Silvia Burlina Enzo Manzato Eugenio Ragazzi Pietro Traldi Annunziata Lapolla 《Journal of mass spectrometry : JMS》2013,48(1):105-110
Increased oxidation of low density lipoprotein (LDL) is characteristic of atherosclerosis. In this frame, high density lipoproteins (HDL) play an important role, being able to remove lipid peroxides (LPOs) and cholesterol from oxidized LDL, so exhibiting a protective role against atherosclerosis. A wide range of reactive compounds lead to the oxidation of methionine (Met) residues with the formation of methionine sulphoxide (MetO) in apolipoprotein A‐I (ApoA‐I). Consequently, the determination of MetO level can give both an evaluation of oxidative stress and the reduced capability of ApoA‐I in LPOs and cholesterol transport. For these reasons, the development of analytical methods able to determine the MetO level is surely of interest, and we report here the results obtained by MALDI mass spectrometry. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
124.
The four stereomer 1-(4-hydroxy-3-methoxy)-phenyl-1,2,3-propanetriols were obtained in about 30% yields starting from ferulic acid by a synthesis based on osmium catalyzed asymmetric dihydroxylation. 相似文献
125.
Roberta Seraglia Pietro Traldi Roberta Bertani Giacomo Facchin Luciano Pandolfo 《Journal of mass spectrometry : JMS》1994,29(11):619-624
A fast atom bombardment (FAB) mass spectrometric study on the open-chain compound 1,3-bis(cyanomethylenetriphenylphosphorane)propane-1,3-dione and on the cyclic zwitterionic compounds 4-oxy-5-triphenylphosphonium-6-methyl-2-pyrone and 4-oxy-5-triphenylphosphonium-6-phenyl-2-pyrone, obtained by reaction of carbon suboxide, C3O2, with stabilized phosphorus ylides, Ph3PCHX (X?CN, COMe, COPh), is described. The FAB mass spectrometric behaviour of these compounds is compared with that shown by tri-phenylphosphoranilideneketene, Ph3P ? C ? C ? O, and by 4-hydroxy-6-methyl-2-pyrone, with the aid of metastable ion data and collision spectroscopy. 相似文献
126.
Mazzeo P Di Pasquale D Ruggieri F Fanelli M D'Archivio AA Carlucci G 《Biomedical chromatography : BMC》2007,21(11):1166-1171
A high-performance liquid chromatographic method for the simultaneous determination of di(2-ethylhexyl)phthalate (DEHP) and its major metabolite mono(2-ethylhexyl)phthalate (MEHP) in seminal plasma was developed and validated. The method involves liquid-liquid extraction followed by isocratic reversed-phase chromatography with diode-array detection. The recovery, selectivity, linearity, precision and accuracy of the method were evaluated from the analysis of spiked seminal plasma samples. The effect of mobile-phase composition and pH on the retention of the target analytes was investigated. The limits of detection were 0.010 and 0.015 microg/mL, for DEHP and MEHP, respectively. This method was used to analyze real samples in support of clinical studies on these potential endocrine disruptors. 相似文献
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129.
Pietro Bollinger Philip Cooper Hans U. Gubler Albert Leutwiler Trevor Payne 《Helvetica chimica acta》1990,73(5):1197-1204
Compound (Z)- 8a has been found to display interesting antiinflammatory activity. In order to prepare derivatives with a wide variety of substituents in the aromatic part of the molecule, a new synthesis of the key intermediates 9a-g was developed starting from thiophene-3-carboxylic acid ( 11 ) and substituted benzyl bromides. The conversion of 9a-g to 10a-g follows a known procedure. Ketones 10a-g , on reaction with alkyl (dialkoxy-phosphoryl)acetate, followed by isomer separation and alkaline ester hydrolysis, yielded the desired derivatives (Z)- 8a-g and (E)- 8a-g . The biologically most interesting compound (Z)- 8a is currently undergoing clinical trials. 相似文献
130.
Guella G Ascenzi D Franceschi P Tosi P 《Rapid communications in mass spectrometry : RCM》2007,21(20):3337-3344
The role of organic impurities in the methanol-to-olefin (MTO) industrial process catalyzed by zeolites is the subject of ongoing debate. We have found that methanol (HPLC and RPE grade) purchased from different chemical companies may contain organic impurities, whose ionization is the dominant process in the positive ion atmospheric pressure chemical ionization (APCI) spectrum of commercial CH(3)OH. Such impurities produce ions with elemental formulae C(n)H(2n+1)O(+) (n = 4, 5, 6); likewise, ionization of tetradeuterated methanol (CD(3)OD) leads to the corresponding fully deuterated series C(n)D(2n+1)O(+) (n = 4, 5, 6), an outcome which represents a clear evidence of their widespread diffusion. We suggest that their formation might be inherent to the chemical process whereby methanol is synthesized on an industrial scale. Mass spectrometry (MS) experiments, gas chromatography/mass spectrometry (GC/MS) analysis and nuclear magnetic resonance (NMR) measurements allowed us to establish that commercial methanol contains dimethyl acetals of simple alkyl ketones, such as propanone, butanone and pentanone. Ab initio calculations (DFT/B3LYP) proved useful to understanding the ionization mechanisms of such impurities. 相似文献