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21.
Summary
UV Densitometric Method for the Determination of Estrogens and Androgens in Pharmaceutical Preparations
A convenient method for the determination of estradiol benzoate/testosterone propionate and of ethynylestradiol/methyltestosterone mixtures from ampoules and lingualets, is described. The procedure is simple since the method involves direct reading from the thin-layer plate, avoiding thus the elution of the spot.After TL Chromatographie separation of active substances, densitometric measurements were performed with a HPTL scanner at 254 nm, whereby good and precise results were obtained. The standard deviation was found to range from 0.022 to 0.183, whereas the relative standard deviation ranged from 0.93 to 2.7%.The results obtained show that the method is applicable to routine analysis. 相似文献
22.
P. M. Nikolić Lj. Milković P. Mihajlović B. Lavrenčić 《Czechoslovak Journal of Physics》1978,28(4):456-459
Zone center optical phonons in SnSe were investigated using Raman scattering data obtained here and previously reported far infrared reflectivity measurements. The values of the ratio of the pairs of interlayer force constants were calculated te be between 3·3 and 4·5. Thus it can be concluded that SnS is a layer like semiconductor but less layer like than GeS, GeSe or SnS. 相似文献
23.
Hans-Christian Mez Günther Rist Jaroslav Kalvoda Otto Ermer Ljubinka Lorenc Mihailo Lj. Mihailovi 《Helvetica chimica acta》1976,59(4):1273-1293
X-ray structure determination of the p-bromobenzoate 2b of one of the (E/Z)-isomeric 3β-hydroxy-5,10-seco-1(10)-cholesten-5-ones confirmed the (E)-configuration proposed previously and showed the cyclodecenone ring to adopt an extended crown conformation of type A 1 (Fig. 9). Analysis of the 1H- and 13C-NMR. spectra of acetate 2a revealed that in solution the ten-membered ring of this steroid exists in at least two distinct forms, the predominant (about 85%) corresponding to the solid-state conformation of 2b (= A 1), and the minor most likely to B 2 (Fig. 9). From NMR. data the energy difference between the two species and the relevant activation energy were estimated. A number of conformational force field calculations using a simplified partial structural model was performed; but the computed energy differences between the various possible conformations do not reproduce the effective situation, neither in solution nor in the crystal lattice, indicating that additional effects such as the transannular interaction of the double bond with the carbonyl group may strongly influence the thermodynamic stability of the system. The conformations deduced were used to rationalize the stereochemical course of different chemical reactions of 2a . 相似文献
24.
25.
G. Schmitz Lj. Kolar-Anić 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(9):1380-1387
It has been known for a long time that the decomposition of hydrogen peroxide catalyzed by hydrogen and iodate ions, the Bray-Liebhafsky
reaction, can generate oscillations in a batch reactor. Recently, mixed-mode oscillations and chaos have also been observed
in a CSTR. The model we had previously proposed to explain the kinetics in a batch reactor can also simulate these new complex
behaviors. Time series give only a limited view of the features of the calculated behaviors and more information is obtained
studying the properties of the state space. We use projections of the trajectories, calculation of the correlation dimension
of the attractor, Poincaré sections, and return maps. As the state space of the model is six-dimensional, we try to answer
the questions of whether the projections into a 3D subspace give correct pictures of the real trajectories and whether we have reasons to prefer a special subspace.
The text was submitted by the authors in English. 相似文献
26.
The structure of [Pt2Cl(CO) (μ-Ph2PCH2PPh2)2] [PF6] was determined by -ray methods and refined to = 0.082, using diffractometric intensities of 5646 independent reflections. The crystals are monoclinic, space group 21/, = 12.919(3), = 15.576(6), = 25.151(5)Å, β = 94.82(3)°, = 4. They are built of octahedral hexafluorophosphate anions and dinuclear platinum(I) cations. The latter contain PtCl and PtCO fragments linked to one another by a PtPt σ-bond and by two bridging bis(diphenylphosphino)methane ligands. The platinum atoms are in square planar environments and the dihedral angle between the two coordination planes is 40.1°. Selected bond lengths are: PtPt 2.620(1), PtCl 2.384(5), PtC 1.89(3) and PtP 2.291(5) – 2.308(5)Å. 相似文献
27.
G. Rasulić S. Jovanović Lj. Milanović D. Petković 《Journal of Thermal Analysis and Calorimetry》1987,32(2):661-669
DSC and DTA techniques have been used to determine nitrogen present in the form of ammonium nitrate in fertilizers. The optimum conditions for the investigations were determined for both techniques. By determining peak area, i.e. the enthalpy of the ammonium nitrate crystal transformation II I, it was possible to determine the nitrogen content in ammonium nitrate and in lime ammonium nitrate by DSC with average deviations of 0.44 and 0.91%,respectively. Using DTA and the enthalpy of the ammonium nitrate crystal transformation IV III, the average deviation of nitrogen determination in lime/ammonium nitrate was 1.09%.
Zusammenfassung DSC und DTA wurden zur Bestimmung des in Düngemitteln in Form von Ammoniumnitrat vorliegenden Stickstoffs benutzt. Für beide Techniken wurden die optimalen Untersuchungsbedingungen ermittelt. Durch Bestimmung der Peakfläche, d. h. der Enthalpie der Kristalltransformation II I des Ammoniumnitrats konnte der Stickstoffgehalt in Ammoniumnitrat und in Kalk/Ammoniumnitrat mittels DSC mit mittleren Abweichungen von 0.44 bzw. 0.91% bestimmt werden. Aus der Kristalltransformation IV III des Ammoniumnitrats ergibt sich bei Benutzung der DTA-Methode eine mittlere Abweichung von 1.09% für die Stickstoffbestimmung in Kalk/Ammoniumnitrat.
, . . , , (III) , — . , , 0,44 0,91%. IVIII , - 1,09%.相似文献
28.
Summary Adsorption properties of alkaline earth-metal modified silica beads were investigated by the gas-solid chromatography (GSC) method. Silica beads, obtained from colloidal material, were characterized by their surface areas, crystallinity and amount of sorbed alkaline earth cations. Retentions of several aliphatic, alicyclic, chlorinated, and aromatic compounds were measured in the temperature range from 373 to 453 K.The gas/solid partition coefficients, K5, and the related thermodynamic functions at zero surface coverage were determined. The results show that the specific surface areas of modified silica samples remain practically constant, whereas the modification leads to a decrease of silica surface heterogeneity. 相似文献
29.
A study of chromium(III) ion adsorption on a stearic acid monomolecular layer (MML), spread on the surface of a51CrCl3 aqueous solution, is presented. From the analysis of the experimental results it can be concluded that MML saturation is achieved at CrCl3 concentrations above 10?6M. When the maximum adsorption pH value of Cr(III) ions on MML is 6.7, MML is completely ionized and chromium ion is bonded as Cr(OH) 2 + . The kinetics of Cr(III) ion adsorption on MML could be expressed as AS=A ∞ S (1?e?k t). 相似文献
30.
Ljubinka Lorenc Lidija Bondarenko-Gheorghiu Natalija Krsti Hermann Fuhrer Jaroslav Kalvoda Mihailo Lj. Mihailovi 《Helvetica chimica acta》1995,78(4):891-898
Upon heating in AcOH, the stereoisomeric (Z)- and (R)-6,9-dioxocyclodex-3-enyl derivatives, 5 and 6 , respectively, obtained by HgO/I2 oxidation of 5-hydroxy-8-oxo-8,14-seco-5α-androstane-3β,17β-diyl diacetate ( 3 ), undergo an unusual intramolecular rearrangement to give the corresponding unsaturated (5R,9R)- and (5R,9S)-spiro-lactones 7 and 8 , respectively. Hydroxylation of the C?C bond in 7 and 8 , and subsequent glycol cleavage of the resulting diols 9 and 10 afforded the epimeric spiro-lactones (5R,9S)- 11 and (5R,9R)- 14 , respectively, and in both cases, the ring-D-containing fragments 12 and 13 . 相似文献