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研究以5 Br PADAP为显色剂,用混合线性分析分光光度法同时测定铜、锌、镍。在pH8.2的硼砂 盐酸缓冲溶液中,Cu2 、Zn2 、Ni2 分别与5 Br PADAP形成稳定的配合物,其吸收光谱相互重叠。用一种新的数学模型,即混合线性分析进行光谱分辨,各组分的纯光谱则用最小二乘法求得。讨论了反应条件、测量波长的选择等因素的影响。铜、锌、镍的标准回收率分别为95.0%~102.5%、94.2%~101.3%和96.2%~104.2%。应用于铝合金中铜、锌、镍的同时测定。 相似文献
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本文探讨和论证了平衡移动法中Amax值对测定配合物组成和稳定常数的影响,确定定当吸光度值A1≤0.8Amax时,在一定测量误差范围内的不同Amax值可得到相同的配合物组成,但对稳定常数测定的影响无法消除,用实例对上加以验证,结果满意。 相似文献
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PLS紫外分光光度法同时测定复方阿斯匹林三组分含量的研究 总被引:1,自引:0,他引:1
复方阿司匹林(APC)是常用的解热镇痛药物,片剂中乙酰水杨酸,咖啡因,非拉西丁的同时测定方法有线性最小二乘法[1],系数倍率法[2]等,由于APC三组分中咖啡因的含量相对较少往往使测定值有较大偏差。本文利用乙酰水杨酸易水解的性质,加入NaOH溶液使之完全水解为水杨酸钠间接求得乙酰水杨酸含量,同时在浓度校正及样品测定时适当增加咖啡因浓度而使各组分浓度差别减小,利用PLS法测定三组分含量。1 PLS法分析原理偏最小二乘法(PartialLeastSquares简称PLS)是一种多组分同时测定的新计算方法。与双波长分光光度法[3],线性规划法[4]比较,它… 相似文献
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随着分子生物学的发展,人们对混合配体配合物越来越重视。经典的Bjerrum形成函数方法,求得的是表观稳定常数,仅考虑了简单配合物,不能反映溶液真实配位平衡,对三元等复杂体系更无能为力。近年用大型计算机程序,可处理多元体系,测定精度提高。稀土在生理和药理方面的应用,也要考虑生物体中的排泄问题。稀土与蛋白质 相似文献
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测定三元配合物组成比的新方法──均匀设计法毛东森(上海石油化工研究院,201208)配合物组成比的测定,对了解配合反应机理、推断配合物结构,具有十分重要的意义。对于只形成一种配合物的二元系统,连续变化法是测定其组成比的一种重要方法。该法用于三元配合系... 相似文献
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由于非水溶剂的应用日趋广泛,促使物理化学工作者对于溶剂和溶液性质进行研究,同时开展了有关物理化学数据的测定和积累工作,以利于指导实践[1]。目前文献报道含水混合溶剂中的电解质活度系数较多,但非水混合溶剂中电解质活度系数报道较少。电解质浓溶液活度系数的计算方法目前应用较广的是Pitzer半经验算法[2]。Pitzer的算法中具体物系的β(0)、β(1)等系数需从实测活度系数数据拟合求得。孙仁义等通过测定汽液平衡盐效应的方法研究了盐在混合溶剂中的活度系数[3-4]。最近孙仁义等[5]提出了双液比固定条件下含盐体系汽液平衡数据热力学一… 相似文献
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A method is proposed for the evaluation of equilibrium parameters from potentiometric data, in which all the sources of random error are taken into account. This means including in the minimized sum the residuals in all the quantities subject to error (titrant volume, emf, parameters of composition of the titrant and titrand, parameters of electrode characteristics, and equilibrium constants known from other experiments). The method of preparation of the solutions is represented by a directed, acyclic graph which allows consideration of the sources of error connected with the composition of the solutions, and avoidance of inconsistency in the composition characteristics. Numerical examples are presented. 相似文献
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The average dimensions and thermodynamic properties of unperturbed ethylene-propylene copolymer chains have been evaluated according to a theory based on a pseudostereochemical equilibrium among the different monomer units. The frequency of occurrence of the ethylene-propylene pairs has been adjusted to the value to be expected from the chemical composition and from the product of the reactivity ratios, while stereochemical equilibrium is assumed for the propylene-propylene sequences. The calculated unperturbed dimensions agree satisfactorily with experimental data. Our results are also in substantial agreement with those recently obtained by Mark who used a different method based on a Monte Carlo routine for sequence generation. 相似文献
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We report the Newton-Raphson based globally convergent computational method for determination of chemical equilibrium composition. In the computation of chemical equilibrium composition, an appearance of nonpositive value of number of moles of any component leads to discrepancy. The process of conditional backtracking and adaptive set of refining factors for Newton-Raphson steps are employed to resolve the problem. The mathematical formulation proposed by Heuze et al. (J Chem Phys 1985, 83, 4734) has been solved using proposed computational method, instead of empirical iterative formulation, as proposed by them. Results for the same numerical example, used by Heuze et al. (J Chem Phys 1985, 83, 4734) and White et al. (J Chem Phys 1958, 28, 751) are presented in addition to decomposition of Cyclotrimethylenetrinitramine for fixed temperature and pressure. It is observed that the proposed method is efficient and globally convergent. An even noteworthy finding is that the set of refining factors can be chosen from the range 0.1 to eta, where eta may be greater than one depending on how smoothly system of nonlinear equations is dependant on corresponding variable. Related analysis and results are discussed. 相似文献
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《Fluid Phase Equilibria》2005,235(1):50-57
We present an application of the recently developed Monte Carlo method for simulations at fixed total enthalpy [W. R. Smith, M. Lísal, Phys. Rev. E 66 (2002) 01114-1–01114-3], combined with the reaction ensemble Monte Carlo method, for the direct prediction of equilibrium reactive adiabatic processes. For the industrially important ammonia synthesis reaction in an adiabatic plug-flow reactor, we perform direct simulations of the equilibrium reaction temperature and the composition of the exit stream as a function of the temperature and pressure of the inlet stream. The chemical species of the system are represented by all-atom potentials with interaction parameters taken from the literature. The accuracy of the molecular model is validated by comparing simulation results with experimental data. We also compare the simulation results with a macroscopic thermodynamic model based on the Soave–Redlich–Kwong equation of state. The simulation results for the reaction conversion show very good agreement with available experimental data over a wide range of temperatures and pressures, whereas the corresponding results from the macroscopic thermodynamic model slightly deteriorate with increasing pressure. Based on these comparisons, the predicted values of the reaction temperature and composition of the exit stream from the simulations are more accurate than the corresponding predicted values from the macroscopic thermodynamic model. 相似文献
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R. S. Kumeev M. Yu. Nikiforov E. D. Totchasov G. A. Al’per 《Journal of Structural Chemistry》2008,49(6):1120-1123
Chemical shifts (c.s.) of 1H nuclei in methanol are measured for methanol-benzene and methanol-phenanthrene systems. A method to determine the equilibrium constant of the molecular association reaction by NMR spectroscopy data is proposed for systems with low solubility of a compound when the dependence of c.s. on the composition is close to a straight line. The equilibrium constants for the formation of molecular complexes in methanol-benzene and methanol-phenanthrene systems are found. 相似文献
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Xiao-hong Han Zan-jun GaoYing-jie Xu Yu QiuXu-wei Min Qin WangGuang-ming Chen 《Fluid Phase Equilibria》2010
Isothermal vapor–liquid equilibrium data of difluoromethane (HFC-32) + ethyl fluoride (HFC-161) mixture in the range of temperatures from 253.15 K to 303.15 K have been measured in the wide range of compositions. The experimental method used for this work is the single-cycle type. Using Peng–Robinson (PR) equation of state, combined with the first Modified Huron-Vidal (MHV1) mixing rule and Wilson model, the vapor–liquid equilibrium data are correlated. The correlation results have a good agreement with the experiment results. The average absolute vapor composition deviation is within 0.0125, and its largest absolute deviation of the vapor composition is 0.0568; the average relative pressure deviation is within 0.76% and its largest relative pressure deviation is 2.87%. In addition, the results reveal that there is no azeotrope in the binary system, and their temperature glides are small. 相似文献
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Kayler ZE Sulzman EW Marshall JD Mix A Rugh WD Bond BJ 《Rapid communications in mass spectrometry : RCM》2008,22(16):2533-2538
The stable isotopic composition of soil (13)CO(2) flux is important for monitoring soil biological and physical processes. While several methods exist to measure the isotopic composition of soil flux, we do not know how effective each method is at achieving this goal. To provide clear evidence of the accuracy of current measurement techniques we created a column filled with quartz sand through which a gas of known isotopic composition (-34.2 per thousand) and concentration (3,000 ppm) diffused for 7 h. We used a static chamber at equilibrium and a soil probe technique to test whether they could identify the isotopic signature of the known gas source. The static chamber is designed to identify the source gas isotopic composition when in equilibrium with the soil gas, and the soil probe method relies on a mixing model of samples withdrawn from three gas wells at different depths to identify the gas source. We sampled from ports installed along the side of the sand column to describe the isotopic and concentration gradient as well as to serve as a control for the soil probe. The soil probe produced similar isotopic and concentration values as the control ports, as well as Keeling intercepts. The static chamber at equilibrium did not identify the source gas but, when applied in a two end-member mixing model, did produce a similar Keeling intercept produced from the control ports. Neither of the methods was able to identify the source gas via the Keeling plot method probably because CO(2) profiles did not reach isotopic steady state. Our results showed that the static chamber at equilibrium should be used only with a Keeling plot approach and that the soil probe is able to provide estimates of uncertainty for the isotopic composition of soil gas as well as information pertinent to the soil profile. 相似文献
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Wei Zong Wang A. B. Murphy J. D. Yan Ming Zhe Rong J. W. Spencer M. T. C. Fang 《Plasma Chemistry and Plasma Processing》2012,32(1):75-96
This paper is devoted to the calculation of the chemical equilibrium composition and thermodynamic properties of reacting
mixtures of carbon and water at high temperature. Equilibrium particle concentrations and thermodynamic properties including
mass density, molar weight, entropy, enthalpy and specific heat at constant pressure, sonic velocity, and heat capacity ratio
are determined by the method of Gibbs free energy minimization, using species data from standard thermodynamic tables. The
calculations, which assume local thermodynamic equilibrium, are performed in the temperature range from 400 to 30,000 K for
pressures of 0.10, 1.0, 3.0, 5.0 and 10.0 atm. The properties of the reacting mixture are affected by the possible occurrence
of solid carbon formation at low temperature, and therefore attention is paid to the influence of the carbon phase transition
by comparing the results obtained with and without considering solid carbon formation. The results presented here clarify
some basic chemical process and are reliable reference data for use in the simulation of plasmas in reacting carbon and water
mixtures together with the need of transport coefficients computation. 相似文献
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This paper presents in detail a robust, efficient and accurate methodology for the computation of equilibrium composition in gaseous mixtures. The methodology is founded on the concept of the chemical basis, which is defined and formalized using a powerful matricial approach. The method is specially designed to be general, thus providing basic thermodynamic data in several areas, such as combustion, plasma chemistry and, more generally speaking, computational fluid dynamics. The performance of the method is given in terms of CPU usage and the computed results are compared with those in the published literature. The method is shown to yield results of very high quality in terms of accuracy and smoothness. 相似文献