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211.
Oxidation of three selected organic model materials, saccharose, gelatine and styrene-divinylbenzene with and without combustion catalysts, was studied with a derivatograph. The catalysts significantly lowered the combustion temperature of the model materials. The amount of carbon dioxide formed during the oxidation process was simultaneously determined gas-titrimetrically. The catalysts used ensured complete carbon to carbon dioxide conversion in the cases of saccharose and gelatine. 相似文献
212.
Summary A global LSER model that relates HPLC retention to mobile phase composition and pH is tested for a varied group of solutes,
both neutral and ionizable, in a polymeric column and methanol-water mobile phases. It is compared to the local LSER model
developed only for a given mobile phase, i.e., a fixed organic modifier content, and to the global LSER model set only for
neutral solutes. The global LSER model for neutral and ionizable solutes requires a few supplementary parameters over the
other models tested, but it accounts for retention under any experimental conditions for a given column and methanol-water
mobile phases, describing properly the interactions established in the HPLC system (hydrophobicity, hydrogen-bond acidity
and basicity, dipolarity/polarizability…).
This paper is number 13 of a series with the same general title: “Retention of Ionizable Compounds on HPLC” published in various
journals. 相似文献
213.
The title compound is a crucial intermediate in the biomimetic conversion of vincadifformine 1 into vincamine 7. Its configuration at C-16 is established by a combination of chemical and spectroscopic evidence. Iodine oxidation converts 14 into the bridged lactam 18, thus proving a β configuration for the hydroxy group at C-16. The same reaction applied to vindoline 19 gives 21 identical with one of the compounds obtained by microbiological transformation of 19. The 13C NMR spectra of derivatives 3 and 8 (obtained by oxidation of vincadifformine) show that oxidation proceeds with introduction of the substituent at C-16, with a β-configuration. The alcohol 3 however, posesses a different conformation due to strong hydrogen bonding with N-4. 相似文献
214.
L. Martinot D. Baré C. Michaux 《Journal of Radioanalytical and Nuclear Chemistry》1993,170(2):389-398
The electrochemical reduction of hexavalent and tetravalent uranium is investigated in ethylammonium nitrate at 298 K and in the acetamide-KSCN eutectic at 400 K. The transient techniques describe a two-step reduction of UO
2
2+
in acetamide-KSCN while only one step is observed in ethylammonium nitrate. The reduction of tetravalent uranium proceeds in one step giving trivalent uranium in the two media. In any cases, additional kinetic phenomena are the source of difficulties for the understanding of the reactions. In controlled potential electrolysis, side-reactions between the reduced species and the solvent impede completely the mechanism foreseen by transient methods. 相似文献
215.
The potential anti-cancer activity of triazines was characterized by the inhibition of the growth of L1210/R71 cells. The retention times for fifteen triazine derivatives were measured by high-performance liquid chromatography on octyl silica and silica gel columns. The slope and intercept values of the plot of the logarithmic capacity factor versus acetonitrile concentration were calculated from the reversed-phase retention measurements. The adsorption properties of the compounds were characterized by the retention data obtained on silica gel columns using high and low concentrations of ammonium salts in the hydro-organic mobile phase. The non-polar, non-polar unsaturated and polar surface areas, the surface energies, the dipole moments and the Van der Waals radii of the molecules were calculated from their chemical structures after energy minimization on the basis of molecular mechanics. Correlation analysis of these parameters showed that the inhibitory effect is dependent on the polar and non-polar surface areas of the molecules. The reversed-phase slope showed a significant correlation with the difference between the accessible and the total non-polar surface areas of the compounds, whereas the intercept values correlated with the non-polar accessible surface area. The adsorption properties of the triazines on silica gel cannot be described by the molecular parameters investigated here. 相似文献
216.
The structures of Beccapoline and Beccapolinium, two new isoquinoline alkaloids from , Annonaceae, have been elucidated by spectroscopic analysis. They are the first examples of natural bisaporphines. 相似文献
217.
A novel support with artificially created recognition for the selective removal of proteins and for affinity chromatography 总被引:4,自引:0,他引:4
Summary Acrylamide and N,N-methylenebisacrylamide were copolymerized in the presence of a protein to form a gel which was pressed through a sieve. The gel particles obtained were packed into a chromatographic tube. The experimental conditions for the polymerization are such that the pores of the gel particles are large enough to permit the protein to diffuse out of the particles, so that the entrapped protein can be removed from the bed by washing with an aqueous solution. However the interaction with the matrix is so strong that the protein can be desorbed only by a buffer containing 0.5 M sodium chloride or by a 10% solution of acetic acid containing 10% SDS. When a sample containing the protein present during the polymerization was applied to the column along with other proteins this protein was the only one adsorbed. The technique worked selectively with hemoglobin, cytochrome C and transferrin. 相似文献
218.
M. A. Pérez 《Zeitschrift fur Physik C Particles and Fields》1983,18(2):113-115
We study the leptonic decay modes of the vectorT b * and pseudoscalarT b t-flavored mesons in the framework of some extended technicolor models and for the standardSU(2)×U(1) model with two complex Higgs doublets. We find that the ratioГ(T b * →? v Г(T →? v) bcan help in discriminating among these models but, unfortunately, the experimental prospects for detecting these decay modes are not very bright. 相似文献
219.
We estimate ψψ production at collider energies in the framework of perturbative QCD. TheO(α s 2 )?(α s 4 ) parton cross-sections, with the non-relativistic approximation for the heavy quark bound states, are used. This first insight into the characteristics of the kinematical distributions allows predictions on the predominance of the quark, gluon orB meson production mechanisms in particular kinematical regions. 相似文献
220.
The nucleophilic reactions of 2,3-dichlorobenzo[b]thiophene 1,1-dioxide with - and -glycols, -diamines, and -amino alcohols proceed with cleavage of hydrogen chloride to give the previously unknown 3-monosubstituted derivatives of 2-chlorobenzo[b]thiophene 1,1-dioxide. The second functional group (the hydroxyl group in amino alcohols) does not enter into the reaction.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1602–1604, December, 1972. 相似文献