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971.
Summary The surface dyeability of the poly(vinyl alcohol) fiber with different degree of formalization was studied by measuring -potential of the fiber in alkaline aqueous solutions (pH 10) of a cationic dye Methylene Blue. With the increase in the dye concentration, the sign of the -potential of the fiber changed from negative to positive and thereafter the positive value approximated to saturated value, and the amount of dye adsorbed (expressed in mol/cm2-fiber) increased also. These results may possibly be attributed to the formation of the electrostatic bond between the fiber and the dye. The linear relations were found between and logC
d
and its slope did not change with rise of temperature. The free energy of dyeing G (negative) calculated from the slope of the -logC
id
curve, etc. increased with increasing the degree of formalization of the fiber. This fact corresponds to the increase in the surface dye adsorption with increasing the degree of formalization. With increasing the degree of formalization, the heat of dyeing H (negative) increased and the entropy of dyeing S (positive) decreased. The positive value of S for each fiber, suggests the formation of hydrophobic bond as a driving force to the dyeing of Methylene blue on the fiber surface in addition to the electrostatic bond.This paper is Part XXVII in a series on Studies on -potentials and Surface Dyeability of Natural and Synthetic Fibers in Dye Solution. Part XXVI: T. Suzawa andK. Kawakami, Nippon Kagaku Kaishi1975, No. 7,1134. 相似文献
972.
A multidimensional GC-system containing two capillary columns of different polarities, operated within a double oven instrument, was used for the optimized separation of complex isomeric mixtures of various types of chlorinated aromatic compounds such as PCB, PCDD, or PCDF. Electron capture was applied parallel to flame ionization detection to obtain sensitive signals of the PCB or PCDD and the n-alkane standards required for identification by Kovats indices, respectively. Electron capture detection within a valvelessly operated MDGC system forced changes in the usual instrumental set-up, the live-switching coupling piece being located within the second oven of the double oven instrument. This oven is operated isothermally to ensure optimal and interference-free detection, for stable flow conditions within the coupling piece and for the determination of the isothermal retention indices (Kovats), which are much more suitable for identification by retention than the so-called “linear” indices. 相似文献
973.
A one-step solid-phase extraction procedure, based on a new silica gel adsorbent modified with cholesterol groups, has been
investigated for measurement of cotinine in urine. Cotinine is the main metabolite of nicotine in the human body and is analyzed
as a biomarker for assessment of direct or passive exposure to tobacco smoke. New cholesterol-modified adsorbents have been
obtained by chemical modification of silica gel of different porosity with cholesterol ligands. Although recovery by this
extraction procedure were optimum over a relatively broad range of sample pH (3.1–8.0), analytical conditions such as sample
loading, washing and elution conditions, concentration of cotinine to be extracted, and the type of adsorbent used for extraction
were found to affect the efficiency of the procedure and had to be controlled for optimum recovery. When these conditions
were controlled, recovery of cotinine from spiked human urine was reproducible and depended on compound ionization. Quantitative
analysis of cotinine was performed by reversed-phase high-performance liquid chromatography with UV detection.
Presented at: Conference of the Hyphenation of Liquid Chromatography–Nuclear Magnetic Resonance Spectroscopy, Liquid Chromatography–Mass
Spectrometry and Related Topics, Tuebingen, Germany, March 25–29, 2006. 相似文献
974.
An accurate estimation of pKa values in methanol-water binary mixtures is very important for several separation techniques such as liquid chromatography and capillary electrophoresis that use these solvent mixtures. In this study, the pKa values of 11 polyphenolic acids have been determined in methanol-water binary mixtures (10%, 20% and 30% (v/v)) by potentiometry, liquid chromatography (LC) and LC-DAD methodology.The results show a similar trend for the pKa values of all the studied compounds, as they increase with increasing concentration of organic modifier, which allows a linear relationship between pKa values and mole fraction of methanol to be obtained. The pKa values obtained in aqueous medium have been compared with those given in the literature, and also with the values predicted by the SPARC on-line pKa calculator. The data obtained have been used to test the feasibility of an estimation of dissociation constants in a methanol-water medium from the relationship between pKa values and the organic cosolvent fraction in the mixtures. 相似文献
975.
Raman spectroscopy was applied for the direct non-destructive analysis of amiodarone hydrochloride (ADH), the active ingredient of the liquid formulation Angoron®. The FT-Raman spectra were obtained through the un-broken as-received ampoules of Angoron®. Using the most intense vibration of the active pharmaceutical ingredient (API) at 1568 cm−1, a calibration model, based on solutions with known concentrations, was developed. The model was applied to the Raman spectra recorded from three as-purchased commercial formulations of Angoron® having nominal strength of 50 mg ml−1 ADH. The average value of the API in these samples was found to be 48.56 ± 0.64 mg ml−1 while the detection limit of the proposed technique was found to be 2.11 mg ml−1. The results were compared to those obtained from the application of HPLC using the methodology described in the European Pharmacopoeia and found to be in excellent agreement. The proposed analytical methodology was also validated by evaluating the linearity of the calibration line as well as its accuracy and precision. The main advantage of Raman spectroscopy over HPLC method during routine analysis is that it is considerably faster and no solvent consuming. Furthermore, Raman spectroscopy is non-destructive for the sample. However, the detection limit for Raman spectroscopy is much higher than the corresponding for the HPLC methodology. 相似文献
976.
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
977.
[RhCl(C8H14)2]2 together with the optically active amidines C6H5C(=NR)NHCH(CH3) (C6H5) I–V or their Li derivatives after activation with molecular hydrogen gives catalysts which at room temperature and 1.1 bar H2-pressure hydrogenate the prochiral substrates (Z)-[N-acetylamino]-cinnamic acid, itaconic acid, -methylcinnamic acid, -methylcinnamic aldehyde, and -methylcinnamic alcohol as well as cyclohexene, benzene and toluene. Good hydrogenation activity of the new catalysts is in contrast to low optical induction which only in the hydrogenation of -methylcinnamic alcohol with 1.5 to 2% leads to values different from zero.
3. Mitt.:H. Brunner undW. Pieronczyk, J. Chem. Res., im Druck. 相似文献
978.
The Electron impact mass spectra of (CO)3 MC6H5—X complexes (M = Cr, W; X = OCH3, OC4H9, CO2CH3, CO2C4H9) were recorded. From metastable transitions and by high-resolution measurements complete fragmentation diagrams were obtained; in some cases comparative structure determinations of fragment ions were carried out by collisional activation. The fragmentation of the tungsten complexes considerably differs from that of the chromium compounds. The differences may be attributed to the stronger-electrophilic character as well as to the more pronounced tendency of tungsten to attain higher oxidation states. 相似文献
979.
Summary In high pressure gas chromatography efficient columns can be packed by the slurry packing technique. However, polysiloxane stationary phases like OV 101 and OV 3 dissolve in the packing liquids. In order to make them suitable for slurry packing these stationary phases have to be made insoluble. This immobilization is achieved by bonding the stationary phases to the surface by means of a high temperature treatment. Successive layers are applied by recoating and are immobilized by a cross-link reaction. A range of loading percentages from 4 upto 20 by weight could be prepared in this way. On the evaluated columns compounds like butanol and dioxane elute as rather symmetrical peaks with the correct values for the retention index, indicating the absence of adsorption effects. Efficiency is good and bleeding rate is low. The columns could be successfully used in the analysis of turpentines. 相似文献
980.
The mercury perrhenates with the empirical formulas HgReO4 and Hg2ReO5 were prepared by annealing powdered mixtures of mercury(II)oxide and mercury(II)metaperrhenate Hg(ReO4)2 in sealed silica tubes. Their crystal structures were determined from single-crystal X-ray data. HgReO4 crystallizes dimeric with nearly linear O3Re? O? Hg? Hg? O? ReO3 molecular units and Hg2ReO5 has a solid state structure, where Hg(I) and Hg(II) together with oxygen atoms form 14-membered rings, which are condensed to two-dimensionally infinite polycationic nets of composition (Hg22+ · 2 HgO)n. These nets are separated from each other by tetrahedral ReO4? anions. 相似文献