Short communication, Note

https://doi.org/10.5599/admet.3.4.209

Application of the Henderson-Hasselbalch equation to solubility determination: NSC-639829 Case Study

Samuel Yalkowsky ; Department of Pharmaceutical Sciences, College of Pharmacy, The University of Arizona, Tucson, Arizona, USA
Raj Patel ; Department of Pharmaceutical Sciences, College of Pharmacy, The University of Arizona, Tucson, Arizona, USA
Doaa Al-Antary ; Department of Pharmaceutical Sciences, College of Pharmacy, The University of Arizona, Tucson, Arizona, USA

Abstract

A number of publications which challenge the applicability of the Henderson-Hasselbalch equation to
saturated solutions have appeared in the last few years (Avdeef [1-3], Butcher et al. [4], and Volgyi et al.
[5]). In the most recent of these, Butcher et al. [4] suggested “the Henderson-Hasselbalch equation may
not always be an accurate predictor of the pH dependence of solubility.” They claimed that the pKa of 4.70
determined by Jain et al. [6] for NSC-639829 is incorrect and that the value of 3.76, which they obtained by
extrapolation of spectrophotometrically determined pKa values in 22, 30, and 41 percent methanol-water
solutions, is the correct value. We believe that 4.70 is the correct value and that there are several serious
flaws in their analysis. These are described below.

Keywords

Hrčak ID:

150560

URI

https://hrcak.srce.hr/150560

Publication date:

30.12.2015.

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