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81.
Riela S Bruno M Rosselli S Saladino ML Caponetti E Formisano C Senatore F 《Journal of separation science》2011,34(4):483-492
The essential oil of different parts of Ferulago campestris (Bess.) collected in Sicily has been extracted by microwave-assisted hydrodistillation (MAHD) and by classic hydrodistillation (HD). A comparative qualitative-quantitative study on the composition of the oils was carried out. A total of 100 compounds were identified in the oils obtained by MAHD, whereas 88 compounds characterized the HD oils. The most prominent components were, in all different parts of F. campestris and in both extraction methods, 2,4,5-trimethylbenzaldehyde and 2,4,6-trimethylbenzaldehyde isomers; the latter was not previously found. The attempt to evaluate where the oil components are located in all parts of the plant was carried out by means of a kinetic study. Then, electron microscopy observation on the different parts before and after MAHD and HD was performed. 相似文献
82.
83.
Aimed to obtain new materials for the conservation of stone substrates, we report here on the synthesis of a polymer which has been obtained by inducing polymerization on a methacrylate monomer functionalized by alchoxysilane groups. Two lithotypes, the Comiso calcarenite and Mistretta quartzite, stones largely used in artworks of north-eastern Sicily, were treated with the above polymer and its conserving efficacy evaluated in terms of porosimetric features, hydric properties and appearance. The collected data were compared to those provided, under the same experimental conditions, by an ethylmethacrylate/methylmethacrylate copolymer and an alkylalchoxysilane, products widely employed in the protection of stones. Experiments aimed to test the durability of the above polymer against UV artificial ageing are also reported. 相似文献
84.
Nonaqueous CE and field-amplified sample stacking have been used in the determination of complex mixtures of polar aromatic sulfonates (AS; mainly benzene- and naphthalenesulfonates) of environmental concern. The analytical procedure consists of an on-column aqueous sample enrichment, followed by the nonaqueous electrophoretic determination of stacked aromatic sulfonates. Various organic solvents were used as separation medium, acetonitrile and N-methylformamide gave the best results. Optimum capillary electrophoresis separation is obtained with ammonium acetate (25 mM) dissolved in N-methylformamide-methanol (90:10) as background electrolyte. This combined method was applied to the analysis of surface water samples spiked with selected aromatic sulfonates derivatives. 相似文献
85.
Dupont J Fonseca GS Umpierre AP Fichtner PF Teixeira SR 《Journal of the American Chemical Society》2002,124(16):4228-4229
1-n-Butyl-3-methylimidazolium hexafluorophosphate room-temperature ionic liquid is not only suitable as a medium for the preparation and stabilization of iridium nanoparticles but also ideal for the generation of recyclable biphasic catalytic systems for hydrogenation reactions. Thus, Ir(0) nanoparticles with a mean diameter of 2 nm have been prepared by reduction of Ir(I) dissolved in the ionic liquid with H2. This catalytic solution can be reused several times for the biphasic hydrogenation of olefins under mild reaction conditions. 相似文献
86.
87.
Bruno Danieli Paolo De Bellis Laura Barzaghi Giacomo Carrea Gianluca Ottolina Sergio Riva 《Helvetica chimica acta》1992,75(4):1297-1304
Quinic acid ( 1a ), shikimic acid ( 2 ), and their derivatives were acylated in organic solvents by several lipases and by the protease subtilisin Carlsberg. The most satisfactory results were obtained with methyl (or benzyl) quinate ( 7a (or 8a )) and lipase from Chromobacterium viscosum adsorbed on Celite, which showed an overshelming preference towards the acylation of OH–C(4). Under optimized conditions, the syntehtically useful 4-O -acetylquinate 8d was isolated in ca. 90% yield. On the other hand, acylation of methyl shikimate ( 10a ) showed no regioselectivity with any of the enzymes tested. A possible rationale for the different behavior of Chromobacterium viscosum lipase towards 7a and 10a is given, comparing the conformations of these two molecules, as deducted from 1H-NMR and molecular-mechanics calculation. 相似文献
88.
Eleonora Freire Sergio Baggio Juan Carlos Muoz Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(5):o259-o262
The structures of the mono‐ and sesquihydrates of 2,6‐bis(1H‐benzimidazol‐2‐yl)pyridine (bbip) are reported. Phase (I), C19H13N5·H2O, has one water and one bbip molecule in the asymmetric unit, while phase (II), C19H13N5·1.5H2O, has three water molecules and two bbip molecules in the asymmetric unit. The compounds exhibit very similar molecular geometries but different packing organizations, which result from intricate hydrogen‐bonding schemes. 相似文献
89.
Eleonora Freire Sergio Baggio Juan Carlos Muoz Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(8):m299-m301
The structure of the title compound, [Ni(ths)(bbip)(dmf)]·H2O [ths is thiosulfate, S2O3; bbip is 2,6‐bis(1H‐benzimidazol‐2‐yl)pyridine, C21H13N5; and dmf is dimethylformamide, C3H7NO], is monomeric, with the nickel ion octahedrally surrounded by an N,N′,N′′‐tridentate bbip molecule, an S,O‐bidentate ths molecule and an O‐monodentate dmf molecule. The H atoms of the hydration water molecule and the amino groups of bbip are involved in hydrogen bonding and determine a spatial organization of broad layers parallel to (001), which are connected by weak interactions. 相似文献
90.
Melani F Giannini I Pasquini B Orlandini S Pinzauti S Furlanetto S 《Electrophoresis》2011,32(21):3062-3069
Electrokinetic chromatography (EKC) allows the separation of closely related substances by the detection of fine effects in analyte-separation system interactions. With the goal of understanding the fine effects involved in separation using a dual cyclodextrin-microemulsion EKC system, an integrated study of NMR and molecular modeling was carried out. The above dual cyclodextrin-microemulsion system was previously used in the separation of clemastine and its related substances and was prepared by the addition of methyl-β-cyclodextrin (MβCD) and heptakis(2,6-di-O-methyl)-β-cyclodextrin (DMβCD) to an oil-in-water microemulsion. The use of DMβCD was shown to be essential in the separation of clemastine from one of its related substance (I(B) ). A molecular modeling study allowed the different affinities of clemastine and I(B) for the two cyclodextrins to be explained. Furthermore, rotating-frame Overhauser effect spectroscopy NMR experiments clearly indicated that besides the primary pseudostationary phase, namely the ionic microemulsion, cyclodextrins acted as a secondary pseudostationary phase. In addition, it was shown that inclusion complexation of sodium dodecyl sulfate (SDS) monomers into the cyclodextrins cavity occurs; differently, the oil (n-heptane) used in the preparation of microemulsion system resulted to be not included into the macrocycle cavity. These experimental results were supported by molecular modeling, which highlighted the preferential inclusion of SDS into DMβCD. On the basis of these results, it was confirmed that, besides its primary role as the ionic carrier in EKC, SDS is involved in inclusion equilibria toward CDs, which can be effective in increasing the system selectivity. 相似文献