The thermodynamic dissociation constants of ambroxol, antazoline, naphazoline, oxymetazoline and ranitidine by the regression analysis of spectrophotometric data |
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Authors: | Meloun Milan Syrový Tomás Vrána Ales |
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Institution: | a Department of Analytical Chemistry, University of Pardubice, Namesti Cs. Legii 565, CZ-532 10 Pardubice, Czech Republic b IVAX Pharmaceuticals, s.r.o. 74770 Opava, Czech Republic |
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Abstract: | The mixed dissociation constants of five drug acids—ambroxol, antazoline, naphazoline, oxymetazoline and ranitidine—at various ionic strengths I of range 0.01 and 1.0 and at temperatures of 25 and 37 °C were determined using SQUAD(84) regression analysis of the pH-spectrophotometric titration data. A proposed strategy of efficient experimentation in a protonation constants determination, followed by a computational strategy for the chemical model with a protonation constants determination, is presented on the protonation equilibria of ambroxol. The thermodynamic dissociation constant pKaT was estimated by non-linear regression of {pKa, I} data at 25 and 37 °C: for ambroxol and 8.25 (4), log and 11.83 (8), for antazoline and 7.83 (6), and 9.55 (2), for naphazoline and 10.63 (1), for oxymethazoline and 10.77 (7), pKa,2T=12.03(3) and 11.82 (4) and for ranitidine and 1.77 (1). Goodness-of-fit tests for various regression diagnostics enabled the reliability of the parameter estimates to be found. |
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Keywords: | Spectrophotometric titration Dissociation constant Protonation Ambroxol Antazoline Naphazoline Oxymetazoline Ranitidine |
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