UV spectroscopic method for determining pK a values of some antipsychotic drugs in water and acetonitrile-water binary mixtures

In this work, the dissociation constants of seven structurally related typical antipsychotic drugs, namely sertindole, olanzapine, fluphenazine, thioridazine, pimozide, mesoridazine and ziprasidone in water and 10, 20, 30 40 and 50 % (v/v) acetonitrile-water mixtures were determined at 298.15 K by UV/pH titration and correlated with the Kamlet and Taft solvatochromic parameters, ?*, ? and ?. The electronic absorption spectra of these drugs were recorded at various pH values (pH = 2.0-12.0) at 210-350 nm. Calibration of the electrode system was done potentiometrically by Gran's method. Data were processed using the program STAR (stability constants by absorbance readings). The results are in good concordance with literature values. © 2013 Springer Science+Business Media New York