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21.
Stavroula Piperaki Anastasios Perakis Maria Parissi-Poulou 《Journal of chromatography. A》1994,660(1-2):339-350
A liquid chromatographic method for the separation of promethazine (PR) and its positional isomer isopromethazine (IPR) is described.PR is an N-substituted phenothiazine with the actions and the uses of the antihistamines (H1-receptor antagonists). IPR is an impurity in the pharmaceutical preparations of PR and must be controlled at a level below 1%. The liquid chromatographic behaviour of PR and IPR on a hydrolytically stable β-cyclodextrin (β-CD) column with respect to mobile phase composition, pH, ionic strength and the nature of the organic modifier was also investigated. Based on the results, conditions were chosen for the isocratic separation of the two isomers. The proposed separation method is simple and rapid and permits the simultaneous determination of PR and IPR. The separation selectivity of a cyclodextrin bonded-phase column was examined. Special attention was devoted to modelling the inclusion complexes of PR and IPR with β-CD in order to predict their optimum orientation within the β-CD cavity. 相似文献
22.
Machado AM Wypych F Drechsel SM Nakagaki S 《Journal of colloid and interface science》2002,254(1):158-164
Two samples of montmorillonite (one of Brazilian origin, BNC1 clay, and the other STX-1, supplied by the Clay Mineral Society Repository (University of Missouri, USA) were allowed to react with biomimetic metalloporphyrins of Fe(III) and Mn(III) in cationic form. The compounds were characterized by several techniques, showing that the metalloporphyrins molecules were adsorbed at the surface of the clay platelet crystals. The catalytic activities of the intercalated complexes for the oxidation of alkane were dependent upon the concentration of the porphyrin immobilized in the clay and factors such as the metal ion species in the porphyrins, choice of solvent, and concentration of the iodosylbenzene oxidant. Good selectivity to cyclohexanol instead of cyclohexanone was observed for the catalytic oxidation of cyclohexane by iodosylbenzene. 相似文献
23.
The loss of a hydrogen atom from ionized 2-methylpropanenitrile is preceded by a drastic rearrangement of the molecular ion. The result of this fragmentation is the generation of two stable structurally different [C4H6N]+ ions, formed via different pathways. Their structures can be established by a careful comparison of the metastable ion spectra, collision activation spectra, and charge stripping spectra from the compound and its three deuterium labeled analogues and from [C4H6N]+ ions generated from reference compounds via electron impact ionization or in selected ion/molecule reactions. 相似文献
24.
Gancitano P Ciriminna R Testa ML Fidalgo A Ilharco LM Pagliaro M 《Organic & biomolecular chemistry》2005,3(13):2389-2392
Valuable organic compounds such as alpha-hydroxy acids are easily synthesised with relevant selectivity enhancement using a sol-gel hydrophobized nanostructured silica matrix doped with the organocatalyst TEMPO: A materials science based synthetic route which cannot be achieved via classical homogeneous synthesis. 相似文献
25.
Maria Jurkiewicz-Herbich 《Journal of Electroanalytical Chemistry》1981,119(2):275-288
Differential capacity and interfacial tension measurements were carried out on mercury for acetone+nitromethane mixtures with KPF6 as a supporting electrolyte. On the basis of Gibbs adsorption equation and Guggenheim's model of the surface phase the composition of the surface layer was estimated for different acetone contents and different charges on the mercury electrode. The results obtained indicate that the positive acetone adsorption is marked at negative charges with maximum at σm=?0.07 C m?2, but is practically non-existent at zero and positive charges. 相似文献
26.
Pochodzalla J Möhlenkamp T Rubehn T Schüttauf A Wörner A Zude E Begemann-Blaich M Blaich T Emling H Ferrero A Gross C Immé G Iori I Kunde GJ Kunze WD Lindenstruth V Lynen U Moroni A Müller WF Ocker B Raciti G Sann H Schwarz C Seidel W Serfling V Stroth J Trautmann W Trzcinski A Tucholski A Verde G Zwieglinski B 《Physical review letters》1995,75(6):1040-1043
27.
Maria Rosaria Enea 《Geometriae Dedicata》1994,51(3):257-286
In this paper we develop a structure theory of algebraic right distributive quasigroups which correspond to closed and connected conjugacy classes
generating algebraic Fischer groups (in the sense of [6]) such that the mappingx x
–1
ax, fora
, is an automorphism of
(as variety). We also give examples of algebraic Fischer groups where this does not happen. It becomes clear that the class of algebraic right distributive quasigroups has nice properties concerning subquasigroups, normal subquasigroups and direct product.We give a complete classification of one- and two-dimensional as well as of minimal algebraic right distributive quasigroups. 相似文献
28.
Maria do Carmo Rangel Varela Milton Francisco de Jesus Filho Fernando Galembeck 《Hyperfine Interactions》1994,83(1):159-167
Mössbauer spectroscopy was used to follow the aging of ferrihydrite with different amounts of acetate, to achieve more crystalline products. Mössbauer spectra of fresh samples did not show any magnetic components. After two years aging, the solids presented crystalline fractions. Hematite formation was inhibited as acetate content increased in solids. For an acetate/iron molar ratio equal to 0.63 goethite was formed instead of hematite. X-ray diffraction confirmed these results. This work shows that synthetic samples can be used for elucidating the anti-hematitic effect of organic matter already detected in soils. 相似文献
29.
Frabetti PL Cheung HW Cumalat JP Dallapiccola C Ginkel JF Greene SV Johns WE Nehring MS Butler JN Cihangir S Gaines I Garbincius PH Garren L Gourlay SA Harding DJ Kasper P Kreymer A Lebrun P Shukla S Bianco S Fabbri FL Sarwar S Zallo A Culbertson R Gardner RW Greene R Wiss J Alimonti G Bellini G Caccianiga B Cinquini L Di Corato M Giammarchi M Inzani P Leveraro F Malvezzi S Menasce D Meroni E Moroni L Pedrini D Perasso L Sala A Sala S Torretta D Vittone M Buchholz D Claes D Gobbi B O'Reilly B 《Physical review letters》1993,71(6):827-830
30.
Frabetti PL Cheung HW Cumalat JP Dallapiccola C Ginkel JF Greene SV Johns WE Nehring MS Butler JN Cihangir S Gaines I Garren L Garbincius PH Gourlay SA Harding DJ Kasper P Kreymer A Lebrun P Shukla S Bianco S Fabbri FL Sarwar S Zallo A Culbertson R Gardner RW Greene R Wiss J Alimonti G Bellini G Caccianiga B Cinquini L Di Corato M Giammarchi M Inzani P Leveraro F Malvezzi S Menasce D Meroni E Moroni L Pedrini D Perasso L Sala A Sala S Torreta D Vittone M Buchholz D Claes D Gobbi B O'Reilly B 《Physical review letters》1993,70(14):2058-2061