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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
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Dr. Alexander Hoffmann Cooper Citek Dr. Stephan Binder Arne Goos Prof. Dr. Michael Rübhausen Oliver Troeppner Prof. Dr. Ivana Ivanović‐Burmazović Prof. Dr. Erik C. Wasinger Prof. Dr. T. Daniel P. Stack Prof. Dr. Sonja Herres‐Pawlis 《Angewandte Chemie (International ed. in English)》2013,52(20):5398-5401
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Redox‐Active Tetraruthenium Macrocycles Built from 1,4‐Divinylphenylene‐Bridged Diruthenium Complexes 下载免费PDF全文
Stefan Scheerer Dr. Michael Linseis Dr. Evelyn Wuttke Sabrina Weickert Prof. Dr. Malte Drescher Dr. Oliver Tröppner Prof. Dr. Ivana Ivanović‐Burmazović Andreas Irmler Prof. Dr. Fabian Pauly Prof. Dr. Rainer F. Winter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9574-9590
Metallamacrocylic tetraruthenium complexes were generated by treatment of 1,4‐divinylphenylene‐bridged diruthenium complexes with functionalized 1,3‐benzene dicarboxylic acids and characterized by HR ESI‐MS and multinuclear NMR spectroscopy. Every divinylphenylene diruthenium subunit is oxidized in two consecutive one‐electron steps with half‐wave potential splittings in the range of 250 to 330 mV. Additional, smaller redox‐splittings between the +/2+ and 0/+ and the 3+/4+ and 2+/3+ redox processes, corresponding to the first and the second oxidations of every divinylphenylene diruthenium entity, are due to electrostatic effects. The lack of electronic coupling through bond or through space is explained by the nodal properties of the relevant molecular orbitals and the lateral side‐by‐side arrangement of the divinylphenylene linkers. The polyelectrochromic behavior of the divinylphenylene diruthenium precursors is retained and even amplified in these metallamacrocyclic structures. EPR studies down to T=4 K indicate that the dications 1‐H2+ and 1‐OBu2+ are paramagnetic. The dications and the tetracation of macrocycle 3‐H display intense (dications) or weak ( 3‐H4+ ) EPR signals. Quantum chemical calculations indicate that the four most stable conformers of the macrocycles are largely devoid of strain. Bond parameters, energies as well as charge and spin density distributions of model macrocycle 5‐HMe were calculated for the different charge and spin states. 相似文献
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An?elija Malenovi? Yannis Dotsikas Marija Maškovi? Biljana Jan?i?–Stojanovi? Darko Ivanovi? Mirjana Medenica 《Microchemical Journal》2011,99(2):454-460
In the current paper the application of multiobjective optimization (MOOP) technique, via Derringer's desirability function, to a microemulsion liquid chromatographic (MELC) method is described. Chromatographic separation of perindopril tert-butylamine and its four impurities was selected as the case study. Central composite design (CCD) with fractional factorial design, ± 0.5 α star design and four replications in central point was applied for a response surface study, in order to examine in depth the effects of the most important factors. As factors that influence the system mostly (i) content of ethyl acetate and (ii) butyl acetate in composite internal phase, (iii) content of sodium dodecyl sulfate (surfactant) and (iv) n-butanol (co-surfactant), as well as (v) pH of the mobile phase were selected. Retention factor of (a) perindoprilat and (b) impurity Y 31 and (c) resolution factor for impurities Y 32 and 33 were chosen for simultaneous optimization. By adjustment of the importance coefficients and weights, according to defined objectives, the optimal mobile phase composition was predicted to be: 0.24% w/v butyl acetate, 0.3% w/v ethyl acetate, 2% w/v SDS, 7.75% w/v n-butanol and pH of the mobile phase 3.7. The sensitivity analysis of desirability function for these optimal conditions was conducted for the first time in LC separations, by applying a sensitivity procedure. The performed sensitivity analysis confirmed that the higher overall desirability does not necessarily mean a better solution. The accuracy of prediction might be affected if the optimal levels of input variables, achieved from several design points, end up with equal settings and different corresponding overall desirability. In our study this was not the issue, which confirmed the adequacy of predicted optimum. 相似文献
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V. M. Marković Ž. Čupić A. Ivanović Lj. Kolar-Anić 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(13):2327-2335
Stoichiometric network analysis (SNA) represents a powerful mathematical tool for stability analysis of complex stoichiometric
networks. Recently, the important improvement of the method has been made, according to which instability relations can be
entirely expressed via reaction rates, instead of thus far used, in general case undefined, current rates. Such an improved
SNA methodology was applied to the determination of exact instability conditions of the extended model of the hypothalamic-pituitary-adrenal
(HPA) axis, a neuroendocrinological system, whose hormone concentrations exert complex oscillatory evolution. For emergence
of oscillations, the Hopf bifurcation condition was utilized. Instability relations predicted by SNA showed good correlation
with numerical simulation data of the HPA axis model. 相似文献
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N. Pejić M. Vujković J. Maksimović A. Ivanović S. Anić Ž. Čupić Lj. Kolar-Anić 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(13):2310-2316
The non-periodic, periodic and chaotic regimes in the Bray-Liebhafsky (BL) oscillatory reaction observed in a continuously
fed well stirred tank reactor (CSTR) under isothermal conditions at various inflow concentrations of the sulfuric acid were
experimentally studied. In each series (at any fixed temperature), termination of oscillatory behavior via saddle loop infinite
period bifurcation (SNIPER) as well as some kind of the Andronov-Hopf bifurcation is presented. In addition, it was found
that an increase of temperature, in different series of experiments resulted in the shift of bifurcation point towards higher
values of sulfuric acid concentration. 相似文献
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Jančić-Stojanović B Rakić T Kostić N Vemić A Malenović A Ivanović D Medenica M 《Talanta》2011,85(3):1453-1460
In this paper a new chromatographic response function (CRF) is designed and proposed for utilization in the optimization strategies. The function capability to represent the overall quality of a experimentally obtained chromatograms was compared to the other two objective functions and proved to give more accurate and reliable results. The new CRF has improved concept of separation and time term estimation. It reflects all important defects of the chromatogram such as the appearance of asymmetrical or overlapping peaks and prolonged elution time and allows the appropriate weighting of each of them. The LC separation of raloxifene and its four impurities was evaluated through the central composite design experimental plan choosing the new CRF to be the only output of the system. The function demonstrated the ability to judge the impact of the complex interactions of the selected chromatographic parameters (acetonitrile content in the mobile phase, sodium dodecyl sulfate concentration in the water phase, pH of the mobile phase and column temperature) on the mixture behavior and led to the determination of the optimal separation conditions. The newly developed CRF proved to have the advanced performances and it presents the important step forward in the optimization of the chromatographic separation. 相似文献
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Masković M Dotsikas Y Malenović A Jancić-Stojanović B Ivanović D Medenica M 《Journal of AOAC International》2011,94(3):723-734
This paper describes the development and validation of a microemulsion liquid chromatography (MELC) method for simultaneous determination of perindopril tert-butylamine and its impurities in bulk active substances and the pharmaceutical dosage form of tablets. An appropriate resolution with reasonable retention times was obtained for a microemulsion containing 0.24% (w/v) butyl acetate, 0.30% (w/v) ethyl acetate, 2% (w/v) sodium dodecyl sulfate, 7.75% (w/v) n-butanol, and 20.0 mM potassium dihydrogen phosphate, the pH of which was adjusted to 3.70 with 85% orthophosphoric acid. Separations were performed on a Nucleosil 120-5 butyl modified (C4), 250 x 4 mm, 5 microm particle size silica column at 40 degrees C, with a mobile phase flow rate of 1.25 mL/min. UV detection was performed at 254 nm. The established method was subjected to method validation, and required validation parameters were defined. Robustness testing, an important part of method validation, was performed as well. Since robustness validation can be conducted using different experimental designs, the Plackett-Burman design was applied due to its possibility of testing many factors at the same time. The validated MELC method was found to be suitable for the simultaneous determination of perindopril tert-butylamine and its impurities in pharmaceuticals. 相似文献
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Ivanović-Šašić AZ Marković VM Anić SR Kolar-Anić LjZ Cupić ŽD 《Physical chemistry chemical physics : PCCP》2011,13(45):20162-20171
By numerically simulating the Bray-Liebhafsky (BL) reaction (the hydrogen peroxide decomposition in the presence of hydrogen and iodate ions) in a continuously fed well stirred tank reactor (CSTR), we find "structured" types of chaos emerging in regular order with respect to flow rate as the control parameter. These chaotic "structures" appear between each two successive periodic states, and have forms and evolution resembling to the neighboring periodic dynamics. More precisely, in the transition from period-doubling route to chaos to the arising periodic mixture of different mixed-mode oscillations, we are able to recognize and qualitatively and quantitatively distinguish the sequence of "period-doubling" chaos and chaos consisted of mixed-mode oscillations (the "mixed-mode structured" chaos), both appearing in regular order between succeeding periodic states. Additionally, between these types of chaos, the chaos without such recognizable "structures" ("unstructured" chaos) is also distinguished. Furthermore, all transitions between two successive periodic states are realized through bifurcation of chaotic states. This scenario is a universal feature throughout the whole mixed-mode region, as well as throughout other mixed-mode regions obtained under different initial conditions. 相似文献