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1.
YAN Xiaomin ZHAO Lin SHAO Jianhui TAN Xin SONG Zhengxiao School of Chemical Engineering Technology Tianjin University Tianjin China Slichem Liquid Material Co. Ltd. Shijiazhuang China 《Chinese Journal of Reactive Polymers》2004,(Z1)
1. INTRODUCTION Methionine, namely 2-amido-4-thiomethyl butyric acid with a structure of CH3SCH2CH2CHCOOH, is one of the essential amino acids and has two natural enantionmers, D and L-methionine. The mixture of L- and D-isomers can be used as analeptics or nutritive additives to maintain the equilibrium of amino acids of feed [1,2]. L-methionine can release active methyl and accelerate the synthesis of choline, which further speeds up the conversion of the lipid accumulated in liv… 相似文献
2.
Ion-exchanger phase Spectrophotometry withp-nitrochlorophosphonazo (CPApN) has been developed for the determination of scandium. The linear range is 1–8 g of scandium in 50 ml of solution, using 0.8 g of resin, with an apparent molar absorptivity of 2.76 × 105 1 mol–1 cm–1. Aluminum and rare earth elements in reasonable amounts do not interfere. The method has been applied successfully to the determination of scandium in alloys, with relative standard deviations of 2–4%. 相似文献
3.
Summary The thin-layer chromatographic behaviour of 28 phenolic compounds was studied on semicrystalline stannic tungstate layers using various solvent systems of which formic acid and n-butanol-formic acid were found to be the most useful for the separation of these compounds. Dimethyl sulphoxide was found to act as a self detector for a number of phenols. An interesting feature of the study of phenols using stannic tungstate is the novel separation of different isomeric compounds. A number of binary, ternary and quarternary separations of bioanalytical and immunophysiological importance have been achieved. 相似文献
4.
NH4^+改型钾丝光沸石及其离子交换性 总被引:1,自引:0,他引:1
用铵盐改型钾丝光沸石,通过X-射线衍射,红外分析,分配系数,离子交换等温线及交换容量等的测定,就其结构及交换性能进行了研究;并与铵改型钠丝光沸石和天然斜发沸石等进行比较,表明NH4^+改型后的钾丝光沸石对K^+具有较高的交换容量和较好的K^+/Na^+分离效果。 相似文献
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6.
J. Skubiszewska-Zięba R. Leboda B. Charmas W Grzegorczyk R. Szmigielski 《Journal of Thermal Analysis and Calorimetry》2006,86(1):187-194
Thermal analysis was used to study thermal behavior of the sulfonated
ion exchange resin Duolite C20 in the hydrogen, sodium and calcium forms.
The aim of this paper was to prepare spherical carbon adsorbents. SEM and
AFM microscopic methods have been applied to describe their surface characteristics.
It was stated that structural parameters of prepared active carbons depend
on the kind of cation present in the resin. The use of calcium form of Duolite
C20 as the initial polymer precursor allowed to obtain the active carbon with
better yield and better developed pore structure compared with other forms
of this ion exchanger. 相似文献
7.
Michael Lämmerhofer 《Journal of chromatography. A》2010,1217(6):814-856
An overview of the state-of-the-art in LC enantiomer separation is presented. This tutorial review is mainly focused on mechanisms of chiral recognition and enantiomer distinction of popular chiral selectors and corresponding chiral stationary phases including discussions of thermodynamics, additivity principle of binding increments, site-selective thermodynamics, extrathermodynamic approaches, methods employed for the investigation of dominating intermolecular interactions and complex structures such as spectroscopic methods (IR, NMR), X-ray diffraction and computational methods. Modern chiral stationary phases are discussed with particular focus on those that are commercially available and broadly used. It is attempted to provide the reader with vivid images of molecular recognition mechanisms of selected chiral selector–selectand pairs on basis of solid-state X-ray crystal structures and simulated computer models, respectively. Such snapshot images illustrated in this communication unfortunately cannot account for the molecular dynamics of the real world, but are supposed to be helpful for the understanding. The exploding number of papers about applications of various chiral stationary phases in numerous fields of enantiomer separations is not covered systematically. 相似文献
8.
T. A. Kravchenko M. Yu. Chaika D. V. Konev L. N. Polyanskii V. A. Krysanov 《Russian Journal of Electrochemistry》2006,42(6):649-657
Electrodeposition of copper into spherical granules of ion-exchange materials KU-23 and KU-2 out of acid sulfate solutions is studied by a method of cyclic voltammetry. It is discovered that the discharge of copper ions in an ion-exchange matrix is characterized by a cathodic overvoltage that is higher than the overvoltage of the same process on a graphite substrate by 0.08 V, which is most probably connected with a limited mobility of ions localized at fixed groups [RSO 3 ? ]. The cyclic voltammogram exhibits an additional cathodic peak in the potential region corresponding to the reduction of single-charged copper ions that form as a result of their accumulation inside pores of the ion-exchange matrix during anodic dissolution of metal deposited previously. It is fixed microscopically that the process of deposition begins at the graphite substrate/ion-exchanger interface and passes into bulk upon the formation of an electron-conducting layer saturated with copper. Preliminary saturation of the ion-exchanger by copper deposited chemically facilitates uniform electrodeposition of copper over the entire volume of pores of the ion-exchange matrix. 相似文献
9.
Georges Grevillot Julia Dzyazko Konstantin Kazdobin Vladimir Belyakov 《Journal of Solid State Electrochemistry》1999,3(2):111-116
A study of the sorption of d-metal ions by titanium phosphate on a platinum electrode shows that the potential of the platinum electrode significantly
influences the uptake of cations by the ion-exchanger. Cathodic polarization leads to a significant increase of the sorption
whereas anodic polarization is accompanied by desorption. Therefore it is possible to perform cycles of sorption and desorption
simply by switching the potential. The results obtained can be explained by the fact that the layer of titanium phosphate
acts as a phase which extracts protons or hydroxide ions. The electrochemical generation of hydroxide ions at negative potentials
can, especially at less acidic pH, lead to the formation of metal hydroxides in the ion-exchanger phase. This interference
is less important at a lower solution pH.
Received: 5 March 1997 / Accepted: 3 April 1998 相似文献
10.
Ferragina C. Cafarelli P. De Stefanis A. Di Rocco R. Petrilli L. 《Journal of Thermal Analysis and Calorimetry》2003,71(3):1023-1034
Long chain trimethylammonium salts can be successfully used as guest molecules to produce mesoporous layered materials when
intercalated in sol-gel zirconium phosphate, an inorganic ion-exchanger. The obtained materials are very similar independently
of the chain length and the synthesis method batch (B) or direct intercalation (DI). They show a good thermal stability, and
a very high interlayer distance if compared with their precursor. By the thermal characterization it can be observed that
the surfactant is lost in two or three steps depending on its position in the host. The layered structure with the expanded
interlayer distance is maintained up to 300°C. From the IR spectra the different surfactant release models for (B) and (DI)
are confirmed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献