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991.
Sami El Deeb Hermann Wätzig Deia Abd El‐Hady Cari Sänger‐van de Griend Gerhard K. E. Scriba 《Electrophoresis》2016,37(12):1591-1608
This review updates and follows‐up a previous review by highlighting recent advancements regarding capillary electromigration methodologies and applications in pharmaceutical analysis. General approaches such as quality by design as well as sample injection methods and detection sensitivity are discussed. The separation and analysis of drug‐related substances, chiral CE, and chiral CE‐MS in addition to the determination of physicochemical constants are addressed. The advantages of applying affinity capillary electrophoresis in studying receptor–ligand interactions are highlighted. Finally, current aspects related to the analysis of biopharmaceuticals are reviewed. The present review covers the literature between January 2013 and December 2015. 相似文献
992.
Ting Zhao Katarzyna Kurpiewska Justyna Kalinowska‐Tłuścik Eberhardt Herdtweck Prof. Dr. Alexander Dömling 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(9):3009-3018
The synthesis of all 20 common natural proteinogenic and 4 otherα‐amino acid‐isosteric α‐amino tetrazoles has been accomplished, whereby the carboxyl group is replaced by the isosteric 5‐tetrazolyl group. The short process involves the use of the key Ugi tetrazole reaction followed by deprotection chemistries. The tetrazole group is bioisosteric to the carboxylic acid and is widely used in medicinal chemistry and drug design. Surprisingly, several of the common α‐amino acid‐isosteric α‐amino tetrazoles are unknown up to now. Therefore a rapid synthetic access to this compound class and non‐natural derivatives is of high interest to advance the field. 相似文献
993.
Austrian medieval silver/copper coins were investigated at their surfaces by energy dispersive X-ray fluorescence analysis
(EDXRF) and at the cross-sections by X-ray microanalysis in the scanning electron microscope (SEM/EDX) in order to estimate
the error occurring when corroded objects of art and archaeology are analyzed on the surface by non-destructive methods. Additionally,
Ag/Cu-standards were treated in diluted sulphuric acid and the depletion of copper on the surface was measured by EDXRF. By
calculating the ratio of the Ag-K/Ag-L intensity the process of blanching could be studied. 相似文献
994.
Determination of Activation Energy for Glass Transition of an Epoxy Adhesive Using Dynamic Mechanical Analysis 总被引:2,自引:0,他引:2
The activation energy associated with the glass transition relaxation of an epoxy system has been determined by using the
three-point bending clamp provided in the recently introduced TA Instruments DMA 2980 dynamic mechanical analyzer. A mathematical
expression showing the dependency of modulus measurements on the sample properties and test conditions has also been derived.
The experimental results showed that the evaluation of activation energy is affected by the heating rate and test frequency,
as well as the criterion by which the glass transition temperature (T
g) is established. It has been found that the activation energy based on the loss tangent (tanδ) peak is more reliable than
on the loss modulus (E
2) peak, as long as the dynamic test conditions do not cause excessive thermal lags.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
995.
Summary A liquid chromatographic method has been developed to separate a series of quinolones which are widely used as veterinary
drugs: danofloxacin, difloxacin, enrofloxacin (and its metabolite ciprofloxacin), marbofloxacin, norfloxacin and sarafloxacin.
Separation was performed by using an end-capped high-purity silica-based C8 column and a mobile phase consisting of acetonitrile-aqueous oxalic acid buffer solution. In order to establish the optimal
conditions for an isocratic separation, a three-factor Doehlert experimental design was applied. Gradient elution was applied
which reduced analysis time. Figures of merit of the method proposed, with fluorimetric detection, were evaluated. 相似文献
996.
A. V. Shevtsov V. Yu. Petukhova S. A. Kutepov V. V. Kuznetsov N. N. Makhova N. E. Kuz'mina G. G. Aleksandrov 《Russian Chemical Bulletin》2000,49(11):1882-1886
A series of complexes ofN-(2-aminoethyl)diaziridines with transition metal salts (Zn2+, Cd2+, Ni2+, Co2+, Mn2+, or Fe2+) were synthesized. Their structures were established by IR and NMR spectroscopy. The structure of bis[1,2-bis(2-aminoethyl)diaziridine]cadmium(II)
diperehlorate was confirmed by X-ray diffraction analysis.
Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1910–1914, November, 2000. 相似文献
997.
N. E. Fouad 《Journal of Thermal Analysis and Calorimetry》2000,60(2):541-547
The thermal behaviour of CrO3 on heating up to 600°C in dynamic atmospheres of air, N2 and H2 was examined by thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy and diffuse reflectance spectroscopy
(DRS). The results revealed three major thermal events, depending to different extents on the surrounding atmosphere: (i)
melting of CrO3 near 215°C (independent of the atmosphere), (ii) decomposition into Cr2(CrO4)3 at 340–360°C (insignificantly dependent), and (iii) decomposition of the chromate into Cr2O3 at 415–490°C (significantly dependent). The decomposition CrO3 → Cr2(CrO4)3 is largely thermal and involves exothermic deoxygenation and polymerization reactions, whereas the decomposition Cr2(CrO4)3 → Cr2O3 involves endothermic reductive deoxygenation reactions in air (or N2) which are greatly accelerated and rendered exothermic in the presence of H2. TG measurements as a function of heating rate (2–50°C min−1) demonstrated the acceleratory role of H2, which extended to the formation of Cr(II) species. This could sustain a mechanism whereby H2 molecules are considered to chemisorb dissociatively, and then spillover to induce the reduction. DTA measurements as a function
of the heating rate (2–50°C min−1) helped in the derivation of non-isothermal kinetic parameters strongly supportive of the mechanism envisaged.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
998.
T. Kleps M. Piaskiewicz W. Parasiewicz 《Journal of Thermal Analysis and Calorimetry》2000,60(1):271-277
Thermogravimetry was employed to study the changes occurring in rubber vulcanizates during devulcanization carried out by
microwave treatment, a new promising method of recycling rubber waste. The thermogravimetric parameters T
i , T
5 and T
p and the compositions of devulcanizates in comparison with vulcanizates were determined. The results obtained allowed estimation
of the degree of destruction of the polymer chains in response to microwave treatment and permitted establishment of the most
advantageous conditions of devulcanization in order to obtain the best properties of rubber devulcanizates for reuse in rubber
processing.
The results demonstrated that thermogravimetry is a very useful method for investigation and control of the microwave devulcanization
process.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
999.
Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 3-methylglutarates were prepared as solids with general formula MC6 H8 O4 ×n H2 O, where n =0–8. Their solubilities in water at 293 K were determined (7.0×10−2 −4.2×10−3 mol dm−3 ). The IR spectra were recorded and thermal decomposition in air was investigated. The IR spectra suggest that the carboxylate
groups are mono- or bidentate. During heating the hydrated complexes lose some water molecules in one (Mn, Co, Ni, Cu) or
two steps (Cd) and then mono- (Cu) or dihydrates (Mn, Co, Ni) decompose to oxides directly (Mn, Cu, Co) or with intermediate
formation of free metals (Co, Ni). Anhydrous Zn(II) complex decomposes directly to the oxide ZnO.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
1000.
Bruch’s membrane is a layer composed of collagen fibers located just beneath the retina. This study validates a strategy used
to map the morphological and adhesion characteristics of collagen fibers in Bruch’s membrane. Atomic force microscopy tips
were functionalized with different chemical groups and used to map the hydrophilic and hydrophobic regions on the surface
of the eye tissue. The largest adhesion forces were observed when tips functionalized with NH2 groups were used. The trend in the adhesion forces was rationalized based on the distribution of different functional groups
in the triple-helical structure of the collagen fibers. The results of this study can be used to design more effective strategies
to treat eye diseases such as age-related macular degeneration. 相似文献