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101.
《Analytical letters》2012,45(18):3264-3271
Abstract A simple, precise, rapid, and low-cost conductometric method for N-acetylcysteine determination in pharmaceutical formulations is proposed. N-acetylcysteine present in pharmaceuticals containing known quantities of the drug was conductometrically titrated in aqueous solution with copper(II) sulphate using a conductometric cell coupled to an autotitrator. No interferences were observed in the presence of common components of the tablets such as sodium monophosphate, saccharine, sodium benzoate, sucrose, and fructose. Recoveries of N-acetylcysteine from various tablet dosage formulations ranging from 98.3 to 102.0% were obtained. 相似文献
102.
103.
The synthesized macrocycle L is the novel fluorescent receptor having the switching ability by the external stimuli as well as having the recognizing ability of various metal ions. In particular, this macrocycle L shows the possibility of the selectivity of metal ions even in the same charge ions of a different metal, and the values of association constant (M−1) of that for metal ions are consistent with the tendency of increasing charge number of metal ion. In addition, the values of quantum yield (ΦF) of metal complexes of macrocycle L were ranged from 0.021 to 0.111 enough to recognize the metal ions in macrocycle L. We know from the fluorescent pH titration of macrocycle L by acid/base that the change of fluorescence intersects at about pH=5. 相似文献
104.
Complex formation between a nanoparticle and a weak polyelectrolyte chain: Monte Carlo simulations 总被引:1,自引:0,他引:1
Serge?Ulrich Abohachem?Laguecir Serge?StollEmail author 《Journal of nanoparticle research》2004,6(6):595-603
Understanding the complexation processes between nanoparticles and polyelectrolytes is an essential aspect in many branches of nanotechnology, nanoscience, chemistry, and biology to describe processes such as nanoparticle stabilization/destabilization and dispersion, water treatment, microencapsulation, complexation with biomolecules for example, and evolution of the interface of many natural and synthetic systems. In view of the complexity of such processes, applications are often based on empirical or semiempirical observations rather than on predictions based on theoretical or analytical models. In this study, the complex formation between an isolated weak polyelectrolyte and an oppositely charged nanoparticle is investigated using Monte Carlo simulations with screened Coulomb potentials in the grand canonical ensemble. The roles of the nanoparticle surface charge density , solution pH and ionic concentration Ci are systematically investigated. The phase diagrams of complex conformations are also presented. It is shown that the polyelectrolyte conformation at the surface of the nanoparticle is controlled by the attractive interactions with the nanoparticle but also by the repulsive interactions between the monomers. To bridge the gap with experiments titration curves are calculated. We clearly demonstrate that an oppositely charged nanoparticle can significantly modify the acid/base properties of a weak polyelectrolyte. 相似文献
105.
Yu Liu Qian Zhang Dong-Sheng Guo Rui-Jie Zhuang Li-Hua Wang 《Thermochimica Acta》2008,470(1-2):108-112
The binding of three nucleobase-modified β-CDs, (i.e., mono(6-ade-6-deoxy)-β-CD 2, mono(6-thy-6-deoxy)-β-CD 3, and mono(6-ura-6-deoxy)-β-CD 4) with four bile salts (deoxycholate, DCA; cholate, CA; glycocholate, GCA; and taurocholate, TCA) were investigated by means of circular dichroism, 2D NMR spectroscopy and calorimetric titration. The results show the binding of host 2 with bile salts is weaker and different from hosts 3 and 4. Enthalpy changes between hosts 2–4 and bile salts are much more favorable than those of native β-CD 1, whereas the entropy changes are unfavorable. 相似文献
106.
Jorge Antonio Guerrero‐Álvarez Wendy Paloma Mas‐Ku Cesar Garcías‐Morales Armando Ariza‐Castolo 《Magnetic resonance in chemistry : MRC》2010,48(5):356-361
The relative acidities of the cis and trans isomers of a series of 1,5‐oxazaspiro[5.5]undecane derivatives were determined by measuring ΔpK in acid‐base titrations followed by 1 H NMR. Relative structural stabilities were determined by measuring substituent chemical shift and γ‐gauche effects in 13C, 15N, and 17O NMR. Crystallographic characterization of a model spiro[5.5]undecane is presented to support the basicity in solid state. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
107.
BZ反应的滴定量热研究 总被引:1,自引:0,他引:1
用滴定热量计考察丙二酸(以下简称MA)-溴酸钾-硝酸铈铵-硫酸振荡体系在不同反应物浓度下周期、诱导期、诱导期放热的变化情况. 发现反应物浓度与周期、诱导期的倒数之间存在着线性关系,并观测到溴酸钾与丙二酸的浓度固定在不同的值时,随着Ce4 浓度的逐渐变稀,振荡周期变短,从动力学理论角度对上述现象进行了分析. 相似文献
108.
The protonation constants for the products of condensation of 2-ethylhexanoic acid with diethylenetriamine or triethylenetetramine were determined by potentiometric titration. The sequence of protonation of the nitrogen atoms in the imidazoline ring was found from the UV, IR, and 13C NMR spectra. 相似文献
109.
G. Rezaei Behbehani 《中国化学快报》2009,20(6)
The interaction of CuC12 to the first 16 residues of the Alzbeimer's amyliod β peptide, Aβ(1-16) was studied by isothermal titration calorimetry at pH 7.2 and 37 ℃ in aqueous solution. 相似文献
110.
络合滴定法测定低压流体输送用镀锌焊接钢管镀锌层重量 总被引:2,自引:0,他引:2
介绍了利用络合滴定法测定低压流体输送用镀锌焊风管镀锌层重量的方法,试样用稀硫酸溶解,在PH1.5 ̄2.0的弱酸性介质中,以磺基水杨酸钠为指标剂,用EDTA滴定铁,调PH为5.5,以PAN为指示剂,用EDTA滴定锌,由EDTA用量求出锌的重量,用GB/T3091-93方法比较,试验结果满意。 相似文献