Determination of the first dissociation constant of 6-benzylaminopurine -: A comparison of methods

The dissociation constant of 6-benzylaminopurine was measured by three independent methods: capillary zone electrophoresis, ultraviolet spectrometry and differential pulse voltammetry. Titration curves, obtained from electrophoretic and spectral data, were evaluated by standard procedure using Henderson-Haselbalch equation and by nonlinear computer fitting. Significantly lower values of standard deviations were obtained by using of computer fitting. Dissociation constant pK(a) =4.01+/-0.03, 4.10+/-0.07 and 4.24+/-0.12 have been obtained for 6-benzylaminopurine from electrophoretic, spectral and voltammetric data, respectively. (C) 2000 Elsevier Science B.V. All rights reserved.