Studies on the exchange characteristics of [Co(NH3)6]3+ in amberlite IRC-50

Summary The exchange of Co(NH₃)₆]³⁺-ions on amberlite IRC-50 resin has been studied at room temperature. For this exchange process the cations are effective in the order: Cs⁺<Rb⁺<K⁺<Na⁺<Li⁺<NH₄ ⁺<Mg²⁺ <Ca²⁺<H⁺ and (C₂H₅)₄N<(CH₃)₄N⁺ ≪Cetyltrimethylammonium-ion <Cetylpyridinium-ion. The logarithm of the selectivity coefficient gives linear graphs when plotted against the radius of the hydrated ions or the reciprocals of theDebye-Hückel parameter?.     

Synthetic analogues of wedelolactone

The syntheses of 7′-methoxy- and 5′,7′,6-trimethoxy-coumarino(3′,4′:3,2)coumarones (IIa and IIb) are described.     

Dynamics of caged ions in glassy ionic conductors

At sufficiently high frequency and low temperature, the dielectric responses of glassy, crystalline, and molten ionic conductors all invariably exhibit nearly constant loss. This ubiquitous characteristic occurs in the short-time regime when the ions are still caged, indicating that it could be a determining factor of the mobility of the ions in conduction at longer times. An improved understanding of its origin should benefit the research of ion conducting materials for portable energy source as well as the resolution of the fundamental problem of the dynamics of ions. We perform molecular dynamics simulations of glassy lithium metasilicate (Li2SiO3) and find that the length scales of the caged Li+ ions motions are distributed according to a Levy distribution that has a long tail. These results suggest that the nearly constant loss originates from "dynamic anharmonicity" experienced by the moving but caged Li+ ions and provided by the surrounding matrix atoms executing correlated movements. The results pave the way for rigorous treatments of caged ion dynamics by nonlinear Hamiltonian dynamics.     

Studies on the determination of diacetyl guanfubase A concentration in rabbit plasma and pharmacokinetics

A gas chromatographic method for monitoring diacetyl guanfubase A in plasma is described. The procedure involved a single solvent extraction of drug from rabbit plasma into ethyl acetate with guanfubase A as an internal standard. The extract was analyzed subsequently on a gas chromatograph equipped with a hydrogen flame ionization detector. The recovery was 86.43% +/- 6.90% (+/- SD); the RSD of within-day and between-day was 2.81%-5.26% and 5.22%-8.24%, respectively; the regression line was linear over the concentration range of 25-200 micrograms/mL, the limit of detection was 10 micrograms/mL. No endogeneous interference was found in chromatograms of the biological samples. This method was applied to the pharmacokinetic study of diacetyl guanfubase A in rabbits.     

Reactions of Vanillin and Vanillal Esters with 6-Quinolylamine and Phenidone

Previously unknown 2-methoxy(or ethoxy)-4-(11-oxo-9-phenyl-7,8,9,10,11,12-hexahydrobenzo[b][4,7]phenanthrolin-12-yl)phenyl esters of carboxylic acids were prepared by ternary condensation of vanillin or vanillal alkanoates with 6-quinolylamine and Phenidone. According to the ¹H NMR spectra, the target products are formed as mixtures of diastereomers.     

Structure analytical methods for quantitative reference applications

The analytical methods mass spectrometry, UV/Vis, IR, Raman, Fluorometry, XRD, Mössbauer, and NMR used to elucidate chemical structure are evaluated regarding their capabilities to be used as primary analytical techniques in quantitative measurements, considering the criteria in the CCQM definition of primary methods. This includes a review of the respective measurement equations, the evaluation of the measurement uncertainty, and a discussion of evidence for the “highest metrological level”, as obtained from intercomparisons in contest with other methods. It is shown that only few methods fulfill the CCQM criteria. Quantitative NMR spectroscopy is one of them and may be considered as a potential primary method as recommended by CCQM because of being free of empirical factors in the uncertainty budget.     

Mass spectrometric study of the pyrolysis of perfluorinated compounds of composition C6F12-C9F20, containing perfluoroisopropyl groups

The primary and final products arising from the pyrolysis of perfluoro-2,4-dimethyl-3-ethylpentane, perfluoro-3-isopropyl-4-methyl-2-pentene, perfluoro-2-methyl-3-isopropyl-2-pentene, perfluoro-2,4-dimethyl-3-heptene, and perfluoro-4-methyl-2-pentene have been studied using low-energy mass spectrometry and chromatography-mass spectrometry. Thermal decomposition of hexafluoropropene oligomers, containing perfluoroisopropyl groups attached to a double bond, occurs via loss of a radical pair to form perfluorodienes, as well as via abstraction of a hexafluoropropene molecule from the iso-C₃F₇ group. A correlation between the principal fragmentation pathway observed under electron impact and the primary process in the main thermolysis pathway was detected only in the case of perfluoro-4-methyl-2-pentene and perfluoro-2,4-dimethyl-3-heptene, which are capable of cleavage of^.CF₃ and^.C₂F₅ radicals, respectively, to give a single possible allyl radical structure.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1037–1041, May, 1990.     

Time-resolved laser-induced fluorescence spectroscopy for enhanced demarcation of human atherosclerotic plaques

We report on the enhanced demarcation between human atherosclerotic plaques and normal vessel wall obtained using time-resolved detection of laser-induced fluorescence rather than the customary time-integrated monitoring technique. A frequency-doubled mode-locked and cavity-dumped continuous wave dye laser was used for picosecond pulse generation at 320 nm, and photon-counting techniques were employed for the time-resolved signal monitoring from human aorta samples in vitro. Implications for imaging fluorescence angioscopy and spectroscopic guidance in laser ablation of plaque are indicated.     

Photometric flow-injection measurements with flow-cell employing light emitting diodes

Summary The flow-injection cell based on a light emitting diode and phototransistor as light source and detector respectively has been constructed and tested. As control procedures bismuth determination with Xylenol Orange and phosphate determination with molybdate and ascorbic acid were described. The working curve may be prepared as a function of absorbance or directly of photocurrent intensity.

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Photometrische Messungen der Durchfluinjektion in einer Durchfluß-küvette mit Hilfe lichtgebender Dioden

Zusammenfassung Eine Durchfluß-Injektionsküvette in Verbindung mit einer lichtgebenden Diode und einem Phototransistor als Lichtquelle bzw. als Detektor wurden hergestellt und geprüft. Zur Prüfung wurden die Wismuthbestimmung mit Xylenolorange sowie die Phosphatbestimmung mit Molybdat und Askorbinsäure verwendet. Die Standardkurve kann als Funktion der Absorbanz oder als Funktion der Lichtstromstärke konstruiert werden.

     

The use of 18O substitution in the characterization of MReO4 molecules. The IR spectrum of matrix-isolated CsReO4

The molecular structure of gaseous CsReO₄ has been studied by matrix isolation IR spectroscopy. The ¹⁸O substitution experiments indicate a bidentate structure of C_2v symmetry in which the perrhenate anion is slightly distorted from the tetrahedral geometry.