Optimized hydrolysis and analysis of Radix Asparagi polysaccharide monosaccharide composition by capillary zone electrophoresis

Using orthogonal design, optimized conditions for the hydrolysis of the polysaccharide from Radix Asparagi were determined, as well as its monosaccharide composition. Optimized hydrolysis conditions were a temperature of 100°C in 1.5 M sulfuric acid solution for 5 h. The resulting monosaccharides were derivatized with 1‐phenyl‐3‐methyl‐5‐pyrazolone, then separated by capillary zone electrophoresis in 40 mM sodium tetraborate buffer (pH 10.1), and detected by ultraviolet absorption at 245 nm. Results indicate that the polysaccharide from Radix Asparagi is composed of xylose, arabinose, glucose, rhamnose, mannose, galactose, glucuronic acid, and galacturonic acid, which differs from published findings. Moreover, xylose, glucuronic acid, and galacturonic acid have not been previously reported in Radix Asparagi polysaccharide. This method is simple, fast, and yields a highly efficient separation. As well, these findings can be applied to quality control of Radix Asparagi and for in‐depth study of the biological activity of Radix Asparagi polysaccharide.     

Metastable zone width and nucleation threshold of aluminium hydroxyfluoride hydrate

This paper considers the metastable zone width (MSZW) of aluminium hydroxyfluoride hydrate (AHF, AlF₂OH.H₂O) crystallizing solution, with a view to identifying suitable conditions for crystal growth. Speciation calculations combined with experimental validations have been used to estimate the degree of saturation at varying pHs leading to the identification of the metastable zone width (MSZW). From the results obtained, the solutions are saturated at pH 3.0 ± 0.3 and remain metastable until the nucleation threshold is reached at pH 5.0 ± 0.3. A narrowing of the MSZW at elevated temperatures has been observed and is attributed to the decrease in AHF solubility with increasing temperatures. This phenomenon was applied to obtain a tripling of the crystal particles in 30 minutes. The pH profile of the crystallizing solution is similar to that of acid/base titration curves and is found to be a quick and accurate method of estimating the MSZW. Using similar terminologies, the equivalent point corresponds to solution saturation while the mid‐point corresponds to the nucleation threshold. These results are applicable in the recovery of fluoride values of spent pot lining.     

Influences of ethanol on the thermodynamics and kinetics in the crystallization of xylitol

The metastable zone and crystal growth rates of xylitol in water were investigated under the influence of small volume fractions of ethanol. The utilization of low amounts of ethanol is necessary to help adding slightly soluble ingredients during the fabrication of xylitol products, e.g. in food industry. Therefore, the metastable zone and crystal growth rates were determined by means of an ultrasound measurement technique and batch crystallization experiments. It can clearly be seen that the addition of ethanol is lowering the solubility of xylitol in water. The higher the volume fraction of ethanol, the lower the solubility. The metastable zone width is increased whereas the smallest investigated ethanol content results in the widest metastable zone. The crystal growth of xylitol is inhibited by the addition of ethanol whereby the crystal growth rates are decreasing with increasing ethanol content.     

Magnetic anisotropy of large floating‐zone‐grown single‐crystals of SrRuO3

SrRuO₃ is a highly interesting material due to its anomalous‐metal properties related with ferromagnetism and its relevance as conductive perovskite layer or substrate in heterostructure devices. We have used optical floating zone technique in an infrared image furnace to grow large single crystals of SrRuO₃ with volumes attaining several hundred mm³. Crystals obtained for optimized growth parameters exhibit a high ferromagnetic Curie temperature of 165 K and a low‐temperature magnetization of 1.6 μ_B at a magnetic field of 6 T. The high quality of the crystals is further documented by large residual resistance ratios of 75 and by crystal structure and chemical analyzes. With these crystals the magnetic anisotropy could be determined.     

A Novel Method to Enhance Metastable Zone Width for Crystal Growth from Solution

A novel method has been found to enhance the metastable zone width of solutions in their supersaturated region in order to grow large size crystals. In which, the incorporation of a small quantity of Ethylenediamine tetra acetic acid (EDTA), a well‐known chelating agent, enhances the zone width significantly due to its chelating action. Also this incorporation reduces the nucleation rate and enhances the growth rate of the crystal. X‐ray rocking curve experiment for the grown crystals reveals that EDTA addition does not affect the crystalline quality. This concept was first realized with Potassium acid phthalate (KAP) solutions and then confirmed with Potassium dihydrogen phosphate (KDP) and Triglycine Sulphate (TGS).     

Crystal Growth of High‐melting Multi‐component Rare Earth‐Transition Metal Intermetallic Compounds from the Melt

The crystal growth of different classes of high melting multi‐component Rare Earth‐Transition Metal‐Compounds by vertical floating zone melting with inductive heating has been investigated. Phase diagram features of the multi‐component systems relevant for the crystallization process have been revealed. The critical zone travelling rate for RENi₂B₂C crystal growth is one order of magnitude smaller than for RE₂TMSi₃ compounds. This is attributed to different solidification modes of both classes of compounds, peritectic and congruent melting, respectively. The crystal perfection, element segregation and selected properties of the bulk crystals such as critical temperature of superconductivity were studied as function of the axis co‐ordinate. In the case of RE₂TMSi₂ plate‐like RESi or RESi₂ precipitates were detected in the single crystalline matrix. They were partially dissolved by annealing and subsequent quenching. The anisotropy of various superconducting and magnetic properties was determined at YNi₂B₂C and TbNi₂B₂C single crystalline specimens.     

Enantiomeric Separations in Capillary Electrophoresis Using 18-Crown-6-tetracarboxylic Acid (18C6H4) as Buffer Additive

An overview is presented of the applicability of the crown ether 18-crown-6-tetracarboxylic acid (18C6H₄) as buffer additive in capillary electrophoresis (CE) for the separation of enantiomers. The chiral selector 18C6H₄ is particularly useful for the separation of racemates having a primary amino function. Unfortunately, the crown ether is no longer commercially available. The synthesis and spectroscopic characterization are therefore described in detail. Moreover, a method is presented for the regeneration of the crown ether after CE application. Some new enantiomeric separations of amino acids i.e. NORLEU, ARG, GLU, m-TYR, and o-TYR are listed and the influence of the pH and temperature of the separation buffer is discussed. An intermediate in the synthetic pathway, namely 18-crown-6-tetracarboxamide, did not exhibit any enantioselectivity in CE.     

Extrapolation of real-space quantum chemical calculations from finite-size supercells to the ideal infinite system. III. Application to two-dimensional systems

A previously presented extrapolation method of the density matrix of a standard finite supercell calculation to an infinite supercell is extended to two-dimensional systems. The density matrix of the finite supercell is transformed into q space where it is interpolated and extrapolated in such a way that all its fundamental properties are guaranteed by construction. The resulting modified density matrix contains information from a continuum of q points in the first Brillouin zone which allows for a more realistic calculation of properties like the total energy E_tot per atom and the band structure ϵ₁(q). It is shown that this more realistic calculation takes better care of the crystal symmetries and is essential in reproducing both important degeneracies in the band structure and rotationally symmetric results. In the special case of π electrons only, an exact analytical solution for the density matrix of the infinite supercell is presented. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 895–911, 1997     

Detection of Catecholic Compounds with Field-ampilfied CZE-Amperometry

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