共查询到20条相似文献,搜索用时 140 毫秒
1.
1 引 言利用分光光度法测定络合物的摩尔吸光系数和稳定常数,通常基于饱和法。对不稳定络合物,因难以得到饱和吸收曲线,给摩尔吸光系数和稳定常数的测定带来困难。我们推导出准确求解不稳定络合物离解度的计算公式,可分别测定出不同浓度络合物溶液的离解度,利用线性回归法求出络合物的摩尔吸光系数,再由校正后的离解度求算络合物的稳定常数,可减小实验过程中的误差,提高测定结果的准确度。本法操作简便、准确度高,可适用于不同组成的络合物体系。利用本法测定了镁、钙、钡与偶氮胂Ⅰ以及钻、镍与变色酸2R络合物的摩尔吸光系数… 相似文献
2.
测定了水溶液中硫氰酸钨(Ⅴ)络合物的吸收光谱,最大吸收波长为405 nm.在盐酸浓度为3.56 mol/L、离子强度为0.088 mol/L的溶液中,硫氰酸钾溶液浓度在0.018~0.088 mol/L范围内,与硫氰酸钨(Ⅴ)络合物的平均摩尔吸光系数△-ε呈函数关系.测得络合物的络合比为14.计算出络合物的各级累积稳定常数和摩尔吸光系数分别为β1=40.73,β2=1.10×103,β3=2.40×104,β4=4.16×105,Δε1=9.33×103,Δε2=9.64×103,Δε3=9.93×103,Δε4=1.10×104(t=17.7℃). 相似文献
3.
以Tween-20为增溶剂,用直接光度法研究了汞与双硫腙络合物的组成,以及该络合物的稳定常数和摩尔吸光系数。测得络合物的最大配位数为4,积累稳定常数分别为:β_1=3.77×10~4,β_2=8.03×10~6,β_3=7.75×10~9,β_4=5.60×10~(12)”。相应的摩尔吸光系数分别为:△ε_1=3.98×10~4,△ε_2=4.18×10~4,△ε=4.25×10~4,△ε_4=4.35×10~4。 相似文献
4.
5.
测定了水溶液中硫氰酸钨(V)络合物的吸收光谱,最大吸收波长为405 nm。在盐酸浓度为3.56 mol/L、离子强度为0.088 mol/L的溶液中,硫氰酸钾溶液浓度在0.018~0.088 mol/L范围内,与硫氰酸钨(V)络合物的平均摩尔吸光系数Δε呈函数关系。测得络合物的络合比为1:4。计算出络合物的各级累积稳定常数和摩尔吸光系数分别为:β_1=40.73,β_2=1.10×10~3,β_3=2.40×10~4,β_4=4.16×10~5,Δε_1=9.33×10~3,Δε_2=9.64×10~3,Δε_3=9.93×10~3,Δε_4=1.10×10~4(t=17.7℃)。 相似文献
6.
7.
8.
9.
10.
11.
显色剂偶氮氯膦 (CPA)常用于碱土金属、过渡金属[1 ] 和稀土金属[2 ] 等的显色分析。本文在研究中发现 ,在pH1 .89的溶液中 ,贵金属钯 (Pd2 +)与配体偶氮氯膦mK(CPAmK)有较灵敏的配位反应。溶液由红色变为兰色 ,配体最大吸收在542nm ,配合物灵敏吸收在 61 9nm ,两波长对比度仅 77nm ,因此在 61 9nm测定波长下 ,反应液中过量的配体 (CPAmK)将对配合物真实吸收产生一定的影响。光谱修正理论是近年来发展起来的分子光谱新分析法[3,4] ,在原理和操作上与其他双波长法不同[5] ,它能够通过光谱强度的校正得出体系中产… 相似文献
12.
Structural and spectroscopic study of 5,7-dihydroxy-flavone and its complex with aluminum 总被引:3,自引:0,他引:3
Castro GT Blanco SE 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(10):2235-2241
The structure, stability and molar absorptivity of the complex formed between AlCl(3) and 5,7-dihydroxy-flavone in methanol were investigated using UV-Vis spectroscopy and the AM1 method. The molar ratio method and Job's method of continuous variation were applied to ascertain the stoichiometric composition of the complex in methanol at constant ionic strength. A 1:2 complex was indicated by both methods. The molar absorptivity and stability constant of the complex were determined using a simple and accurate procedure that requires solutions having the ligand and metal ion in the stoichiometric proportion. The high stability constant demonstrates that the complexation reaction is total. The structure of this complex, obtained by the quantum semi-empirical AM1 method, indicates that two classes of metal-ligand interactions are involved in the formation of the metal complex: (a) two simple covalent bonds between the aluminum atom and the oxygen atoms of o-hydroxyl groups of 5,7-dihydroxy-flavone; (b) two stronger Coulombic interactions between the aluminum atom and the carbonyl oxygen atoms of the ligand. 相似文献
13.
A new graphical method is proposed for differentiating mononuclear and polynuclear complexes as well as for determining the stability constant of any complex A(m)B(n). The method is based on the effect of dilution on the degree of dissociation of the complex. The resultant mathematical equation provides a simple graphical calculation which leads to the determination of the stability constant and also the molar absorptivity of the complex. 相似文献
14.
A new mathematical approach to the treatment of spectrophotometric data for differentiation between mononuclear and polynuclear metal complexes in solution is presented. The slope of a straight line yields the total number of units in the complex, from which the true molecular formula can be obtained if the empirical formula is known. The formation constant is also given by the slope of a straight line. The method can be applied to complexes with any number of different ligands. Solutions are prepared in which the ratio of total concentrations of the reacting species is equal to the combining ratio. Spectrophotometric data must be obtained under conditions where only one complex is formed and the degree of dissociation is significant. The molar absorptivity must be obtained by direct measurement. 相似文献
15.
Hong-Wen Gao 《Journal of Analytical Chemistry》2000,55(10):958-963
The biological dye, naphthol blue black B (NBBB) was found to produce a sensitive reaction with copper(II) at pH over 7. This
reaction was very interesting. The complexation of Cu(II) with NBBB happened at pH between 6 and 11 but the redox catalytic
reaction happened at pH over 11, where copper(II) served as a catalyst. In this study, ordinary spectrophotometry was limited
for use because of the serious interference of excess reactant. A new method, Β-correction principle, was applied because
it can eliminate the above interference. This method can give the simple determination of properties of Cu-NBBB complex solution
at pH 9.5, which involved the complex ratio, real molar absorptivity, and stability constant (K). Results showed that the
formed Cu-NBBB complex occurred as Cu(NBBB) at pH 9.5, its real rather than apparent absorptivity was equal to 7.62 x 103 L mol-1 cm-1 at 630 nm, and its stability constant was 1.32 x 106. The redox catalytic reaction between Cu(II) and NBBB at pH 13 was used to determine trace amounts of copper in water. This
reaction was very sensitive and highly selective. Most of the metals did not interfere with the direct determination of copper.
The detection limit of copper was 0.002 mg/L, and the recovery was between 90 and 104% with the relative standard deviation
of less than 11%.
This article was submitted by the author in English. 相似文献
16.
氯冉酸可见分光光度法快速测定酮康唑 总被引:1,自引:0,他引:1
建立了快速测定酮康唑含量的可见分光光度法。实验结果表明:酮康唑与氯冉酸在甲醇-丙酮混合溶剂中发生电荷转移反应,产物的最大吸收波长是524 nm,表观摩尔吸光系数为1.04×103L·mol-1·cm-1。酮康唑质量浓度在20~400 mg·L-1范围内服从比耳定律,相关系数为0.9995。当酮康唑浓度为200 mg·L-1时,五次测定结果的相对标准偏差为1.03%。测得荷移络合物的组成比和稳定常数分别为1∶1和3.9×103。回收率在98.0%以上。本方法简便、快速、准确,可作为制剂的质量控制方法。 相似文献
17.
《Journal of Coordination Chemistry》2012,65(7):1102-1114
The complexation of a recently synthesized aminoxanthone derivative, 1-({2-[(2-aminoethyl)amino]ethyl}amino)-6-methyl-9H-xanthen-9-one with Cu(II) in methanol and water solutions, was investigated by spectrofluorimetric and spectrophotometric methods. The possible molecular geometries, bindings, and spectroscopic properties for the formed complex were theoretically studied in detail by the Hyperchem program. The stoichiometry of the complex was determined from spectrophotometric molar ratio methods at 20°C. The spectral data were further treated by KINFIT program to calculate the formation constant of the 1:3 complex and its molar absorptivity. Program DATAN was used to calculate the spectral behavior of the complex in each solution for different mole ratios. A simple equation for the determination of complex stability constant was also evaluated from titration data. Under the optimal conditions, the ligand can be used as a fluorometric indicator for measuring Cu2+ ions in aqueous solution. 相似文献
18.
The report was the first to establish the new method for the selective determination of trace amounts of metal using the substitution reaction in metallic complex. The reactions between copper(II) and 1-(5-bromo-2-pyridylazo)-2-naphthol-6-sulphonic acid (BPANS) and between ferrous(II) and BPANS at pH 3.5 were studied. In absence of any masking reagent, the recommended method was selective in the determination of trace amounts of copper with Fe-BPANS complex as chromogenic reagent because copper(II) can substitute Fe from Fe-BPANS complex to form Cu-BPANS complex. The ordinary spectrophotometric method was unsuitable to the substitution reaction because the excess of Fe-BPANS complex had the high absorption and affected seriously the absorption of Cu-BPTANS complex. The spectral correction principle may eliminate the above influence to give the simple determination of the composition ratio, stepwise absorptivity (epsilon) and stability constant (K) of metal complex. For analysis of samples, the recovery of copper was between 96.5 and 106% with R.S.D. less than 5%. 相似文献
19.
A method for the extraction-spectrophotometric determination of palladium with 2,2′-dithiodianilline (DTDA) is described. DTDA–Pd(II) complex is extracted from an aqueous solution with pH 3 into isobutyl methyl ketone (IBMK) layer. The absorbance is measured at 397 nm and the molar absorptivity found to be 1.47×106 l mol−1 cm−1. The complex system conforms to Beer's law over the range 0.3–220 ng ml−1 palladium (II). The effect of pH (1–6), NaClO4 concentration, DTDA concentration and shaking time were studied. The ratio of the metal ion to ligand molecules in the complex and its stability constant were found to be 1:1 and 1.45×106, respectively. The tolerance limit for many cations and anions have been determined. Finally the method has been applied successfully to the determination of palladium in synthetic mixtures, alloy and catalyst samples. 相似文献
20.
Castro GT Blanco SE Arce SL Ferretti FH 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(12):2685-2696
The complexation reaction between AlCl(3) and 2,4-dihydroxy-benzophenone with varying permittivity and ionic strength of the reaction medium was investigated by theoretical and experimental procedures, namely, density functional (DFT) and UV-vis spectroscopic methods, respectively. The stoichiometric composition of the complex formed, which was determined by means of the molar ratio method, is 1:1. The molar absorptivity and stability constant of the complex were determined using a method designed by the authors. It was observed that the stoichiometric composition of the complex does not change with the used solvents and that the stability constant in methanol is higher than ethanol. Kinetic experiments in solutions with different ionic strength were also performed. The results obtained permit to conclude that the complex is formed through of a mechanism whose rate-determining step is a reaction between two ions with opposite unitary charges. In the theoretical study performed at the B3LYP/6-31G(d) level of theory using Tomasi's model, it was proposed that the formation of the complex involves one simple covalent bond between the aluminum atom and the oxygen atom of o-hydroxyl group of the ligand and a stronger coulombic attraction (or a second covalent bond) between the central atom and the carbonyl oxygen atom of 2,4-dihydroxy-benzophenone. Using the calculated magnitudes, it was predicted that the complex formed has higher thermodynamic stability in methanol than ethanol. It was also concluded that the planarity of the chelate ring favors a greater planarity of 4-hydroxy-benzoyl group of the complex with respect to the ligand, which agrees with the observed batochromic shifts. The formulated theoretical conclusions satisfactorily match the experimental determinations performed. 相似文献