A multiwavelength spectrophotometric (WApH) titration method for determination of acid dissociationconstants (p avalues) of ionisable compounds developed previously was applied in the case of pyridinederivatives of pharmaceutical interest. Specifically, UV absorption spectra of the drug solution are acquired inthe course of a pH-metric titration using an optical device based on a fibre optics dip probe, a light source and diode array detector. Target factor analysis was applied to deduce the p avalues from the spectral datarecorded at different pH. Using this technique, the p avalues of six pyridine derivatives were determinedsuccessfully. It was demonstrated that the WApH technique in this case outperforms conventional pH-metricmethods with respect to the measurement of p avalues of the sparingly water soluble samples reported in thisstudy. 1999 Elsevier Science B.V. All rights reserved. 解離常數/油水分配系數(pKa/LogP)測定儀