Thermodynamic dissociation constants of isocaine, physostigmine and pilocarpine by regression analysis of potentiometric data

Studies on equilibrium of anthranilic acid in aqueous solutions and in two-phase systems: Aromatic solvent–water

“…Moreover, the Hamilton R-factor reaches the value of 0.1354%. This is another confirmation of an excellent fit (for a good fitness, the Hamilton R-factor reaches the value ≤ 1%, and for excellent fitness is lower than 0.5% [31]). …”

“…The proper statistical analysis, recommended by many authors [27][28][29][30][31], was conducted in order to demonstrate the reliability of the obtained dissociation constants and the results are presented in Table 1. Sensitive criteria of the reliability of the dissociation constant are the Hamilton R-factor and the mean of absolute values of residuals [30].…”

The thermodynamic dissociation constants of methotrexate by the nonlinear regression and factor analysis of multiwavelength spectrophotometric pH-titration data

“…The factor analysis in the INDICES programme predicts the correct number of light-absorbing components when the data quality is high and the instrumental error is known. Three thermodynamic dissociation constants were estimated by nonlinear regression of {pK a , I} data: for methotrexate pK a1 T = 2.895 (13), pK a2 T = 4.410 (14), pK a3 T = 5.726 (15) at 25 o C and pK a1 T = 3.089 (15), pK a2 T = 4.392 (12), pK a3 T = 5.585 (11) at 37ºC, where the figure in brackets is the standard deviation in last significant digits. The reliability of the dissociation constants of the drug were proven by conducting goodness-of-fit tests of the multiwavelength spectrophotometric pH-titration data.…”

“…In previous work [11][12][13][14][15][16][17][18][19] the authors have shown that the spectrophotometric method in combination with suitable chemometric tools can be used for the determination of protonation constants β r or acid dissociation constants K a even for barely soluble drugs. Spectrophotometry is a convenient method for K a determination in very diluted aqueous solutions (about 10 -5 to 10 -6 M), provided that the compound possesses pH-dependent light absorption due to the presence of a chromophore in proximity to the ionisation centre cf.…”

Recent Progress in the pKa Estimation of Druglike Molecules by the Nonlinear Regression of Multiwavelength Spectrophotometric pH-Titration Data

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. In previous work [21][22][23][24][25][26][27][28][29][30][31][32][33], the authors have shown that the spectrophotometric method can be used in combination with suitable chemometric tools for the determination of protonation constants β qr or acid dissociation constants pK a , even for sparingly soluble drugs.…”