Table of Contents
SRX Pharmacology
Volume 2010 (2010), Article ID 527013, 14 pages
Research Article

The Thermodynamic Dissociation Constants of Clotrimazole, Terbinafine HCL, Acetylsalicylic Acid, Salicylic Acid, and Galanthamine by the Nonlinear Regression of Multiwavelength Spectrophotometric pH-Titration Data

1Department of Analytical Chemistry, University of Pardubice, 532 10 Pardubice, Czech Republic
2Recordati Group, Herbacos Bofarma, Ltd., Štrossova 239, 530 02 Pardubice, Czech Republic

Received 29 December 2009; Revised 12 January 2010; Accepted 26 January 2010

Copyright © 2010 Milan Meloun et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The mixed dissociation constants of five drugs—clotrimazole, terbinafine HCl, acetylsalicylic acid, salicylic acid, and galanthamine—at various ionic strengths I and at temperatures of 25°C and 37°C were determined with the use of multiwavelength and multivariate treatments of spectral data SPECFIT/32 nonlinear regression analysis and INDICES factor analysis. The factor analysis in the INDICES program predicts the number of components, when the data quality is high and the instrumental error is known. The thermodynamic dissociation constant pKaT was estimated by nonlinear regression of {pKa,I} data at 25°C and 37°C: for clotrimazole pKa,1T = 4.38(1) and 4.16(3); for terbinafine HCl pKa,1T = 4.19(3) and 4.12(5); for acetylsalicylic acid pKa,1T = 3.49(25) and 3.41(15); for salicylic acid pKa,1T = 3.01(1) and 3.00(1) and for galanthamine pKa,1T = 8.21(1) and 7.99(2) where in brackets the standard deviation is in the last significant digits. Goodness-of-fit tests for various regression diagnostics enabled the reliability of the parameter estimates found to be proven. Pharma Algorithms predicts pKa being based on the structural formulae of drug compounds.