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Investigations of selected properties of pharmacologically active compounds by chromatographic and potentiometric methods on the chrysin example

100%
Pusz J., Zapała W., Papciak B.
Polish Journal of Chemical Technology
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2008
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vol. 10
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issue 1
41-44
EN
The RP-TLC method was used to determine the dissociation constant of chrysin (5,7-dihydroxyflavone) in methanol-aqueous (1:1 v/v) solutions. In this method the pK value was quantified on the basis of retention data and a retention model. The accuracy of determining the model parameters was analysed using the following statistical criteria: the sum of the squared differences between the experimental and theoretical data, approximation of standard deviation, and the Fisher test. Besides, in this work the potentiometric method was used. Investigations were carried out at ionic strength I=0.1 at T= 298 K. The dissociation constant were determined using the Rossotti method as well as the numerical method based on the procedures of non-linear curve fitting using Microsoft Excel Solver and the user-defined function. It has been found that the differences in the evaluated pK values were relatively small and did not exceed 1.2%.
2
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Re-evaluated data of dissociation constants of alendronic, pamidronic and olpadronic acids

100%
Boichenko A., Markov V., Kong H., Matveeva A., Loginova L.
Open Chemistry
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2009
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vol. 7
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issue 1
8-13
EN
The dissociation constants of (4-amino-1-hydroxybutylidene)bisphosphonic (alendronic) acid, (3-(dimethylamino)-1-hydroxypropylidene)bisphosphonic (olpadronic) acid and (3-amino-1-hydroxypropylidene)bisphosphonic (pamidronic) acid were obtained in aqueous solutions (0.10 M KCl) and micellar solutions of cetylpyridinium chloride (0.10 M CPC) at 25.0°C. With the exception of the third dissociation constant of alendronic acid, the dissociation constants of alendronic, olpadronic and pamidronic acids in aqueous solutions matched literature data. The possibility of sodium alendronate determination by acid-base titration by NaOH solution was theoretically grounded on the basis of re-evaluated data of alendronic acid dissociation constants. [...]
3
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Voltammetric and potentiometric studies of some sulpha drug-Schiff base compounds and their metal complexes

75%
Ghoneim M., Mabrouk E., Hassanein A., El-Attar M., Hesham E.
Open Chemistry
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2007
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vol. 5
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issue 3
898-911
EN
The electrochemical behavior of some sulpha drug-Schiff bases at a mercury electrode was examined in the Britton-Robinson universal buffer of various pH values (2.5–11.7) containing 20% v/v) of ethanol using DC-polarography, cyclic voltammetry and controlled-potential electrolysis. The DC-polarograms and cyclic voltammograms of the examined compounds exhibited a single, 2-electron, irreversible, diffusion-controlled cathodic step within the entire pH range which is attributed to the reduction of the azomethine group-CH=N- to -CH2-NH-. The symmetry transfer coefficient (α) of the electrode reaction and the diffusion coefficient (D 0) of the reactant species were determined. The electrode reaction pathway of the compounds at the mercury electrode was suggested to follow the sequence: H+, e−, e−, H+. The dissociation constant of the sulpha drug-Schiff bases, the stability constant and stoichiometry of their complexes with various divalent transition metal ions (Mn2+, Co2+, Ni2+, Cu2+ and Zn2+) were determined potentiometrically at room temperature. [...]
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