Principles of Method Selection in Partition Studies

Publisher Website
Google Scholar
Abstract
An integrated set of experimental methods is described which allows the determination of octanol/water partition coefficients for compounds of diverse structural type having log P values in the range – 1.3 to +4.6. This set has the advantage over a single technique of extending the scope and/or efficiency of log P measurement. A series of defined procedures for selecting the most appropriate method for a particular compound is described.The methods, which are all modifications of established techniques, are described in detail. The “Filter Chamber” technique is a quick and accurate method for log P measurement in the range ˜ −1.3 to +2.8. The “Spectrophotometric pH Profile” allows the “Filter Chamber” range to be extended to ˜ +4.6 by measurement of the extent of partitioning at pH values where the compound is partially ionised. The third technique, “Potentiometric Partition”, relies on potentiometric rather than spectrophotometric detection and hence has applications in determination of the log P of compounds with no chromophore. Each method is exemplified by measurements on simple organic molecules having known pKa and log P values.