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Simple and sensitive spectrophotometric methods for the assay of retinol have been presented. The first method was based on the reaction of retinol with iodine to give a molecular charge-transfer complex, the retinol acting as n-donor and iodine as -electron acceptor. The second method depends on the formation of a highly coloured stable radical anion between retinol and 7,7,8,8-tetracyanoquinodimethane (TCNQ as a -electron acceptor. The molecular ratios of the reactants in the complexes have been established and the experimental conditions leading to maximum charge-transfer bands were also studied. Beer's law is obeyed over the retinol concentration range 2.5–26 µg/ml. The proposed procedures have been applied successfully to the analysis of drug formulation. The average recovery and average standard deviation was 99.99 ±1.13% with retinol-iodine and 100.001 ± 1.31% with retinol-TCNQ. A kinetic study was performed by heating retinol at 50°C for different periods of time, the result obtained by plotting log c against time indicates that thermal decomposition of retinol is of first order. The results obtained by both methods were in good agreement with those obtained by the official method. The developed procedures were found to be simple, accurate and precise and can be used for the determination of retinol in presence of its degradation products. 相似文献
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Potentiometric pH titrations (I = 0.15 M NaNO3; 37°C) have been employed to study the various complex equlibria in the systems involving pyridoxamine and histidine with Co(II), Ni(II), Cu(II), and Zn(II). The stoichiometry and formation constants of different species have been determined with the aid of MINIQUAD-75. The complexes obtained were mostly protonated and positively charged. The formation of the ternary species is discussed in terms of the binary species. They were also correlated with the quaternary species involving pyridoxamine, glycine, and imidazole. Spectral analysis of the complex solutions of different compositions are also reported. The relevance of these ternary complex equilibria to some biological functions is discussed. 相似文献
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Fathi M. A. M. Aqra Shakeel A. Shah Sartaj Tabassum Rasheed M. A. Q. Jamhour Khwaja S. Siddiqi Osama Al-Jowder Fawzia Al-Saleh 《Transition Metal Chemistry》1995,20(2):123-125
Summary New ionic bimetallic complexes of the type [Cu(en)2]-[MCl4], where M = CuII, ZnII, CdII and HgII, were prepared by reacting bis(ethylenediamine)copper(II) dichloride (1 mol) with copper, zinc, cadmium and mercury dichlorides (1 mol) in absolute alcohol. Elemental analyses, conductivity and magnetic susceptibility measurements, and spectroscopic data (such as i.r., u.v.-vis. and e.p.r.) confirm that the compounds are 22 electrolytes in MeOH and that the copper(II) ion is paramagnetic, maintaining its square-planar geometry, while metal ions in the anionic moiety of the complexes achieve their usual tetrahedral environment. An augmented magnetic moment has been observed in the [Cu(en)2] [CuCl4] complex, which is attributed to the ferromagnetic effect and TIP.Author to whom all correspondence should be directed. 相似文献
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Fawzia Boudah Khlifa Abdeddaim Moulay-Hassane Guermouche 《Journal of separation science》1981,4(5):247-248
In this work, we have investigated the influence of the polarities and structures of 13 polysiloxanes on the retention of some N-TFA N-butyl esters of amino acids. Gehrke [1] was the first to examine the possible relationship between polarity and retention data of amino acid derivatives for 9 stationary liquid phases. He concluded that the molecular structure of the stationary liquid phase is an important factor determining retention. 相似文献
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El-Sayed H. El-Mossalamy Fawzia M. Al-Nowaiser Shaeel A. Al-Thabaiti Abdul O. Al-Youbi Suliman N. Baschel Abdulla Y. Obaid 《Monatshefte für Chemie / Chemical Monthly》2007,138(9):853-857
Summary. The new polymer containing cyano groups was synthesized by γ-irradiation. The oximated polymer was prepared using hydroxylamine
hydrochloride in basic medium. The characterization of monomer, polymer, and oximated ones was confirmed by infrared and nuclear
magnetic resonance spectroscopy. The complex formation of the amidoxime salt towards ZnII, CuII, and ZnII/CuII mixture in aqueous solution was studied by atomic absorption spectroscopy, energy dispersive spectroscopy, and electron spin
resonance spectrometry. The significant binding capacity of these metal ions revealed its selectivity to Zinc(II) ion. The
thermal stability of polymers and complexed ones was investigated using thermogravimetry analysis. The change in their morphology
was observed by scanning electron microscopy (SEM). 相似文献
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Two sensitive, selective, economic, and validated spectrofluorimetric methods were developed for the determination of ebastine
(EBS) in pharmaceutical preparations depending on reaction with its tertiary amino group. Method I involves condensation of
the drug with mixed anhydrides (citric and acetic anhydrides) producing a product with intense fluorescence, which was measured
at 496 nm after excitation at 388 nm. 相似文献