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渐进因子分析—PH—分光法测定多元酸的离解常数 总被引:2,自引:1,他引:1
根据多元酸平衡体系中型体具有先出现先消失的特点,提出了用渐进因子分析与化学平衡结合迭代。从PH-分光矩阵中解多元酸离解常数的新方法。用该法测定了多元酸茜素S和铬天青S的离解常数,并讨论了确定型体存在区域的经验式。结果表明该方法稳定,可靠、算法收敛快、所测得的离解常数与文献值吻合。 相似文献
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各级离解常数均大于10~(-7),而且相邻两级的离解常数之比K_(a1)/K_(a2)只有几十倍的多元酸与强酸混合情况下,提出通过测量多元酸的半中和点,分别测定各组分酸含量的酸碱滴定法。 相似文献
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智能求解未知多元酸各级离解常数的研究 总被引:2,自引:0,他引:2
本文介绍了一种新的测定未知多元酸各级离解常数的通用方法。该方法实验上采用苛性碱电势滴定多元酸,计算上采用Gordon数学模型和单纯形最优化方法。并为此编制了一名为"GORDANACID"的计算机程序。 相似文献
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本文提出了一种利用β-CD包结物与酸碱离解平衡关系,用荧光法间接测定β-CD包结物解离常数的新方法。并测定了β-CD分别与1-萘酚和2-萘酚负离子包结物的解离常数pKb为2.58和3.27,β-CD与分子型体1-萘酚和2-萘酚包结物的酸式离解常数pKc分别为10.42和0.68。 相似文献
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偶氮氯膦-mA(CPA mA)离解作用的研究 总被引:6,自引:0,他引:6
本文用pH电位法和分光光度法研究了偶氮氯膦-mA的六级离解作用,测定了其逐级电离常数,计算了离解过程的热力学参数△G°、△H°、△S°,同时与对硝基偶氮氯膦的离解常数进行了比较,其结果与量子化学计算基本相符。 相似文献
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测定平衡常数多采用电导法、冻点法或反应速率法等。用离子选择电极测定平衡常数或离解常数多集中研究各种氟络合物。用硫电极测定平衡常数的工作仅见到测SnS_3~(2-)的平衡常数。我们在对硫电极研究的基础上,用pH玻璃电极测定溶液的pH值,用pS电极测定不同pH值溶液中的[S~(2-)]浓度,根据H_2S在溶液中的平衡理论及硫电极在溶液中的响应特性,找到一种推算H_2S离解常数的途径。 相似文献
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渐进因子分析—分光光度法测定Fe^3+—SCN^—络合物的稳定常数 总被引:2,自引:0,他引:2
本文利用渐进因子分析与化学平衡相结合的方法迭代求解逐级生成络合物的各级稳定常数,对Fe^3+-SCN^-体系在水溶液及50%丙酮溶液中的配体浓度-波长的两维双线性吸光度数据矩阵进行处理,求得水溶液中该络合物第一、二级稳定常数为1gk1=2.26,1gk2=1.30。同时该法还可确定各种组分的存在区间及吸收光谱,本文还对丙酮的存在对Fe^3+-SCN^-络合物的影响作了研究,结果表明丙酮,对高配位络 相似文献
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A potentiometric method using a glass electrode has been applied to determination of apparent ionization constants for water in binary mixtures of water with tetrahydrofuran, methanol, 1,3-propanediol, glycerol, sucrose, and glucose at 25°C. Further calculations with these apparent ionization constants, which are now based explicitly on the previously implicit assumption that ionization of the organic component is negligible compared to ionization of water, permit evaluation of ionization constants for several very weak acids in purely aqueous solvent. Resulting pK values derived from this work and from our earlier work are as follows: glucose (12.38), sucrose (12.75 and 12.80), glycerol (14.05 and 14.07), ethylene glycol (14.44 and 14.52), methanol (15.2), 1,3-propanediol (14.8 and 15.0), 1-propanol (15.1), 2-propanol (15.7), and 2-methyl-2-propanol (15.0). 相似文献
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E. A. Burstein 《Photochemistry and photobiology》1996,63(3):278-280
Abstract— A novel algorithm (QUENCH) is described that resolves fluorescence spectra into components differing in the accessibility (the Stern-Volmer constants) for small quencher molecules. In contrast to the known algorithms, QUENCH first evaluates Stern-Volmer constants of the components using the total set of intensities in spectra measured at several quencher concentrations and then calculates contributions of each component in the emission intensities at every wavelength value. The component spectra, revealed with QUENCH in the tryptophan fluorescence of ribosomal S7 protein, are very similar to the log-normal components calculated using the SIMS program (Abornev, S. M. and E. A. Burstein Mol. Biol. [Engl, transl.] 26, 890-897 1992). The QUENCH method is applicable for the component resolution of fluorescence spectra of any liquid system containing fluorophores of different accessibility to small quenchers. 相似文献
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Sodium salts of 2,3-quinoxalinedithiol have been prepared and used for determination of the acid ionization constants by potentiometric titration. The fully protonated form of the reagent was used in an alternative determination of the first ionization constant by a solubility method. The constants are pK(2), == 6.84 +/- 0.04 and pK(2) = 9.95 +/- 0.03. 相似文献
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A general method has been developed to determine the ionization constants of polymer thin films based on the stimuli-responsiveness of the polymer. Robust polymer films were fabricated on silicon wafers and gold slides using perfluorophenyl azide (PFPA) as the coupling agent. The ionization constants were measured by a number of techniques including ellipsometry, dynamic contact angle goniometry, and surface plasmon resonance imaging (SPRi). Using poly(4-vinylpyridine) (P4VP) as the model system, P4VP thin films were fabricated and the ionization constants of the films were measured taking advantage of the pH responsive property of the polymer. The pK(a) determined by ellipsometry, ~4.0, reflects the swelling of the polymer film in response to pH. The pK(a) value calculated from the dynamic contact angle measurements, ~5.0, relies on the change in hydrophilicity/hydrophobicity of the films as the polymer undergoes protonation/deprotonation. The pK(a) value measured by SPRi, ~4.9, monitors in situ the change of refractive index of the polymer thin film as it swells upon protonation. This was the first example where SPRi was used to measure the ionization constants of polymers. 相似文献
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Wortmann A Jecklin MC Touboul D Badertscher M Zenobi R 《Journal of mass spectrometry : JMS》2008,43(5):600-608
We describe an approach for the determination of binding constants for protein-ligand complexes with electrospray ionization mass spectrometry, based on the observation of unbound ligands competing for binding to a protein target. For the first time, dissociation constants lower than picomolar could be determined with good accuracy by electrospray ionization mass spectrometry. The presented methodology relies only on the determination of signal intensity ratios for free ligands in the low mass region. Therefore, all the advantages of measuring low masses with mass spectrometry, such as high resolution are preserved. By using a reference ligand with known binding affinity, the affinity of a second ligand can be determined. Since no noncovalently bound species are observed, assumptions about response factors are not necessary. The method is validated with ligands binding to avidin and applied to ligands binding to p38 mitogen-activated protein kinase. 相似文献
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Niazi A Ghalie M Yazdanipour A Ghasemi J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,64(3):660-664
The acidity constants of Alizarine Red S in water, water-Brij-35 and water-SDS micellar media solutions at 25 degrees C and an ionic strength of 0.1 M have been determined spectrophotometrically. To evaluate the pH-absorbance data, a resolution method based on the combination of soft- and hard-modeling is applied. The acidity constants of all related equilibria are estimated using the whole spectral fitting of the collected data to an established factor analysis model. DATAN program applied for determination of acidity constants. Results show that the pKa values of Alizarine Red S are influenced as the percentages of a neutral and an anionic surfactant such as Brij-35 and SDS, respectively, added to the solution of this reagent. Effect of surfactant on acidity constants and pure spectrum of each component are also discussed. 相似文献
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Malagoli M Coropceanu V da Silva Filho DA Brédas JL 《The Journal of chemical physics》2004,120(16):7490-7496
We present a multimode vibrational analysis of the gas-phase ultraviolet photoelectron spectra of the first ionization in anthracene, tetracene, and pentacene, using electron-vibration constants computed at the density functional theory level. The first ionization of each molecule exhibits a high-frequency vibronic structure; it is shown that this regularly spaced feature is actually the consequence of the collective action of several vibrational modes rather than the result of the interaction with a single mode. We interpret this feature in terms of the missing mode effect. We also discuss the vibronic coupling constants and relaxation energies obtained from the fit of the photoelectron spectra with the linear vibronic model. 相似文献