Experimental Techniques

A great step forward has been achieved since the pioneering work of Meyer [3] and of Overton on the partitioning of anesthetics in olive oil/water [4], Hansch, Fujita and their coworkers chose the 1-octanol/water solvent system as an arbitrary standard for expression of lipophilicity [10, 11], and pioneered its measurement by the shake-flask technique. Most of the available data refer to this partitioning system. This standard technique, sometimes laborious and precarious, can efficiently and quite safely be sub-

Table 1. Lipophilicity parameters and their recommended symbols

Referred Symbol

Parameter

Alternatives

log P

partition coefficient of neutral species3

log K, log PC

log Poa

log P for 1-octanol/water

log PaIk

log P for alkane/water

log D

distribution coefficient: "apparent" partition8

log P', log Papp

coefficient

log Docl

log D for 1-octanol/water

log Da|k

log D for alkane/water

log P+

partition coefficient of cationic form

log P

partition coefficient of anionic form

log P+/"

partition coefficient of zwitterionic form

CLOGP

log P calculated by the CLOGP programb

log k

log of capacity factor in RP-HPLC

log k„

log k extrapolated to 100 % aqueous eluent

a) log P and log D can be calculated one from the other using the appropriate correction for ionization [1], b) Reference [19], a) log P and log D can be calculated one from the other using the appropriate correction for ionization [1], b) Reference [19], stituted by various chromatographic techniques: thin-layer chromatography (TLC), reversed-phase high performance liquid chromatography (RP-HPLC or RPLC), and centrifugal partition chromatography (CPC), which are all employed routinely.

0 0

Post a comment