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971.
Modified natural diatomaceous earth (DE) is a principal component of the stationary phase in normal thin-layer chromatography (TLC) applications and is mixed with commercial silica gel 60GF254 (Si-60GF254). Modification is carried out by flux calcination and refluxing with acid. Natural DE, modified DEs [flux calcinated (FC)DE and FCDE-I), and Si-60GF254 are characterized by scanning electron microscopy and Fourier-transform-IR spectroscopy. Particle size, specific surface area, pore distribution, pore volume, and surface hydroxyl group density parameters of materials are determined by various techniques. FCDE-I and Si-60GF254 are investigated for their usefulness in the stationary phase of TLC both individually and in composition. Commercially available red and blue ink samples are run on layers of Si-60GF254 and FCDE-I individually, and on various FCDE-I and Si-60GF254 mixtures. Butanol-ethanol-2M ammonia (3:1:1, v/v) and butanol-acetic acid-water (12:3:5, v/v) mixtures are used as mobile phases. The polarities of stationary phases decrease, and the retention factor (Rf) values of ink components increase when the FCDE-I content of the stationary phase increases. The properties of the stationary phase can be optimized by adding FCDE-I to Si-60GF254. This study may be useful in understanding both the systematic effects of stationary phase properties [e.g., specific surface area and surface hydroxyl group density, aOH(s)] and those of the mobile phase (e.g., polarity and acidity) on Rf values and the separability of components. 相似文献
972.
Summary. Group 2B transition metal complexes of bis[N-(2,6-diisopropylphenyl)imino]acenaphthene (o,o-iPr2C6H3-BIAN), namely, [Hg(o,o-iPr2C6H3-BIAN)Cl2] (1), [Zn(o,o-iPr2C6H3-BIAN)2](ClO4)2 (2), and [Cd(o,o-iPr2C6H3-BIAN)2](ClO4)2 (3) have been synthesized and characterized. In complexes 2 and 3, IR, NMR, and conductivity measurements confirm the coordination of two (o,o-iPr2C6H3-BIAN) ligands to the metal center with two discrete perchlorate anions. X-Ray crystal structure of 1 indicates a distorted tetrahedral geometry with two nitrogen atoms from (o,o-iPr2C6H3-BIAN) ligand and two chloride atoms coordinating to the Hg(II) center. 相似文献
973.
Adelina Ianculescu Ana Brăileanu M. Crişan P. Budrugeac N. Drăgan G. Voicu D. Crişan V. E. Marinescu 《Journal of Thermal Analysis and Calorimetry》2007,88(1):251-260
In order to obtain pure and fine BaTiO3
powders with controlled morphology, sol-precipitation methods involving the
use of titanium iso-propoxide and of two different barium sources, i.e. barium
nitrate and barium acetate, were proposed in this work. The thermal behaviour
of the synthesized gels and the X-ray diffraction data obtained for the oxide
powders pointed out that, by using Ba(NO3)2
as barium source, the decomposition process was completed at lower temperature
(750°C) and was accompanied by a more pronounced tendency to obtain a
single phase BaTiO3 composition, by comparison with
the synthesis where barium acetate was used as raw material (1100°C).
Scanning electron microscopy investigations emphasized the effect of the nature
of barium source and synthesis conditions on the morphology of the oxide powders,
as well as on the microstructure of the related ceramics. 相似文献
974.
We have addressed two important issues of nonlinear cross-talk and baseline adjustment in DNA data processing. An important aspect in the processing of the four-dye fluorescence-based data is the cross-talk filtering. Typically, a matrix M, which is a function of the fluorophores and the fluorescence detection system, is used in the multicomponent analysis. In this deconvolution process the matrix is applied directly to the raw signal, on a linear cross-talk assumption. This necessitates the signal to be aligned to the baseline before the filter is applied. The various techniques used for aligning the raw data have the negative effect of adding distortion to the signal. An algorithm for cross-talk removal is presented in this paper. The algorithm uses the intensity difference of the signal rather than the actual value itself, thus making the cross-talk removal possible before the base line adjustment. In addition, a supplementary filtering step is proposed in order to account for the nonlinear nature of the cross-talk. This second step is based on a matrix T that accounts for the correlation of each of the signals with the other three. The overall result is a more precise presentation of the DNA data and less information loss through filtering. 相似文献
975.
In this study, a simple and sensitive fluorimetric method was described for the determination of Ascorbic Acid (AA). The procedure is based on the reaction between AA and Methylene Blue (MB). The fluorescence intensity of MB was measured at excitation and emission of 664 and 682 nm, respectively. MB concentration was decreased as a function of decreasing fluorescence intensity due to forming colorless form of MB (Leuco-MB) in the reaction between AA and MB. A linear relationship was obtained between the decreasing fluorescence intensity and the concentration of AA in the range of 3.0 x 10(-7)-6.0 x 10(-6) mol.l(-1). The detection limit was 2.5 x 10(-7) mol.l(-1). The proposed method was applied successfully for the determination of AA in Vitamin C tablets. 相似文献
976.
Seda Çetindere Süreyya O. Tümay Adem Kılıç Mahmut Durmuş Serkan Yeşilot 《Journal of fluorescence》2016,26(4):1173-1181
A new type of fluorescent chemosensor based on tethered hexa-borondipyrromethene cyclotriphosphazene platform (HBTC) linked via triazole groups was designed and synthesized. Its sensing behavior toward metal ions was investigated by ultraviolet-visible and fluorescence spectroscopies. Addition of a Fe2+ ion to a tetrahydrofuran solution of HBTC gave a visual color change as well as a significantly quenched fluorescence emission, while other tested 19 metal ions induced no color or spectral changes. This compound was found to be highly selective and sensitive for Fe2+ with a low limit of detection (2.03 μM) which is, to the best of our knowledge, the superior than the previously studied chemosensors for Fe2+. 相似文献
977.
The synthesis and characterization of peripherally ({1-[(Z or E)-phenylazo]-2-naphthyl} oxy) tetra-substituted metal-free and metallo (Zn(II), Co(II) and Cu(II)) phthalocyanines are described in this study. Aggregation properties of these compounds were investigated in the concentration range of 20–1 μM in tetrahydrofuran. Spectroscopic and photophysical properties of these phthalocyanines have been investigated in tetrahydrofuran. Thin films of metallophthalocyanines were prepared by spin coating technique. Results show that transmittance values of the films change with respect to the metal ions in the visible and Q absorptions regions. Films were also annealed at 100, 200 and 300 °C and their optical properties were investigated as a function of annealing temperature. The spectrophotometric measurements of transmittance spectra were carried out in the wavelength range 200–1000 nm. Results showed that transmittance values of ZnPc thin films were increased as a result of heat treatment. 相似文献
978.
Mustafa Okumuş 《Molecular Crystals and Liquid Crystals》2016,625(1):117-125
The 6CB/8CB/8OCB liquid crystal mixture has been studied by Differential Scanning Calorimetry (DSC), polarised optic microscopy (POM), Semiconductor Characterization System, and Ultra-violet spectrophotometry (UV). DSC and POM results indicate that the 6CB/8CB/8OCB mixture exhibits liquid crystalline properties. The capacitance-voltage and conductance-voltage measurements were performed in the frequency range of 200-500 kHz and in the temperature range of 30oC–50oC. The 6CB/8CB/8OCB mixture showed an extremely large positive dielectric anisotropy. The molar absorptivity ? for the 6CB/8CB/8OCB mixture was calculated and found to be higher than the absorptivity values of the binary mixtures due to the alkyl chain length with H-aggregation. 相似文献
979.
Tülay Erişir Mehmet Ali Güngör Murat Tosun 《Advances in Applied Clifford Algebras》2016,26(4):1179-1193
In this study, we first calculate the polar moment of inertia of orbit curves under one-parameter planar motion in the generalized complex plane \({{\mathbb{C}_p}}\) and then give the Holditch-type theorem for \({{\mathbb{C}_p}}\): When the fixed points \({X}\) and \({Y}\) on the moving plane \({{\mathbb{K}_p} \subset {\mathbb{C}_p}}\) trace the same curve \({k}\) with the polar moment of inertia \({{T_X}}\), the different point \({Z}\) on this line segment \({XY}\) traces another curve \({{k_Z}}\) with the polar moment of inertia \({{T_Z}}\) during the one-parameter planar motion in the fixed plane \({{\mathbb{K}'_p} \subset {\mathbb{C}_p}}\). Thus, we obtain that the difference between the polar moments of inertia of these curves \({( {{T_Z} - {T_X}} )}\) depends on the only the \({p}\)-distances of this points and \({p}\)-rotation angle of the motion, \({{T_X} - {T_Z} = {\delta _p}ab.}\) 相似文献
980.