The mixed dissociation constant of naphazoline is determined at various ionic strengths I [mol dm−3] in the range of 0.01 to 0.26 and at temperatures of 25°C and 37°C using ESAB and HYPERQUAD regression analysis of the potentiometric
titration data. A strategy of efficient experimentation is proposed in a protonation constant determination, followed by a
computational strategy for the chemical model with a protonation constant determination. Two group parameters, L0 and HT were ill-conditioned in the model and their determination is therefore uncertain. These group parameters, L0 and HT, can significantly influence a systematic error in the estimated common parameter pKa and they always should be refined together with pKa. The thermodynamic dissociation constant pKaT was estimated by nonlinear regression of {pKa, I} data at 25°C and 37°C: for naphazoline pKalT = 10.41(1) and 10.13(2). Goodness-of-fit tests for various regression diagnostics enabled the reliability of the parameter
estimates to be found.
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The clay mineral montmorillonite has been tested as modifier for the carbon paste electrode with a novel electrode modification technique. The differential pulse voltammetric determination of copper(II) by means of this modified carbon paste electrode has been studied. A detection limit of 4×10-8 mol/l has been achieved after 10 min preconcentration under open circuit conditions with subsequent anodic stripping voltammetry. The calibration curve for Cu(II) is linear in the range of 4×10-8–8×10-7 mol/l. Pb interferes in a 10-fold molar and Cd and Hg in a 100-fold molar excess. The interference by humic ligands is significant. 相似文献
The Körner-Kuroda model of the electromagnetic structure of octet 1/2+ baryons is restored on a more topical physical basis. Electromagnetic radii of baryons under consideration are calculated and compared with other model predictions. By an incorporation of a two-cut approximation of correct form factor analytic properties and nonzero vector-meson widths, the Körner-Kuroda model is unitarized, providing in this manner imaginary parts of the octet 1/2+ baryon form factors to be nonzero just starting from a branch point corresponding to the lowest threshold. 相似文献
Summary A photometric method is described for determining the oxygen balance in oxide superconductors. It is based on the oxidation of Fe2+ to Fe3+ by the superconductors and the following determination of the residual Fe2+ ions as complex with 1,10-phenanthroline. Hydrobromic acid is used for dissolving the samples. The method has been developed for 10 mg sample weights. Good reliability of the method was verified by comparison with the cerimetric determination using 80 mg samples. 相似文献
We present a computer study of the association behavior of copolymer chains with a gradient part and soluble tail of variable length. As a simulation method we use dynamic Monte Carlo simulation on a simple cubic lattice with pair interaction parameters. The solvent quality and selectivity is modeled by the variation of pair interaction parameters between nearest neighbors on the lattice. The role of the length of soluble part in the self‐assembly and its effect on the structure of aggregates was the main goal of this work. The size and structure of aggregates were analyzed using an improved topological classification method which has been developed and tested in the present study. The structure and association numbers of aggregates were compared with those of linear diblock copolymers.
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