Figure 4.7 Octanol-water Bjerrum plots for a monoprotic (a) acid and (b) base. The volumes of octanol and water are equal, so that the difference between the apparent pKa and the true pKa is about equal to the partition coefficient. [Avdeef, A., Curr. Topics Med. Chem., 1, 277-351 (2001). Reproduced with permission from Bentham Science Publishers, Ltd.]

they may be further refined by a weighted [117] nonlinear least-squares procedure [153].

The pH-metric procedure has been validated against the standard shake-flask method [150,357], and many studies using it have been reported [56,149151,153,161,162,224,225,229,246,250,268,269,275,276,280,281,324-363]. Determinations of values of log P as low as —2 and as high as +8 have been documented [161,162,352]. The published literature clearly indicates that the Dyrssen technique is a reliable, versatile, dynamic, and accurate method for measuring log P. It may lack the speed of HPLC methods, and it cannot go as low in log P as the CV


25oC 0.15M KCl

0 0

Post a comment