For the weak acids, Britton-Robinson pH 8 buffer (identified in the table as BR-8) was selected for the aqueous phase to ensure that the drug was in a protonated state, whereby the drug would be in a concentration below saturation for proper partitioning. Similarly, for the weak bases, Britton-Robinson pH 3 buffer (identified as BR-3) was selected for the aqueous phase to ensure the drug was de-protonated for partitioning with the organic phase. In each experiment, the final pH of the aqueous phase was measured, and is included in Table where appropriate. In many cases, either the drug did not adequately dissolve in the organic phase, or the measured concentration was below the limit of quantification. In those instances, logD cannot be calculated from an indeterminate fraction, and is therefore represented by a "-".