Hydrophobicity parameters determined by reversed-phase liquid chromatography. XV: optimal conditions for prediction of log P(oct) by using RP-HPLC procedures.
The use of log k derived from reversed phase (RP)-HPLC retention times provides a convenient method for estimating log P(oct) values (P(oct): 1-octanol/water partition coefficient). In order to establish optimal HPLC conditions, the difference between chromatographic (C18 modified column and aqueous methanol eluents) and bulk solvent systems was examined by use of a batch-like equilibration with octane/aqueous methanol. Comparison of values for log P(O/M-W) (log P for the Octane/MeOH-Water partitioning system) and log k measured for monosubstituted pyrazines at different methanol concentrations, showed closest correlation (r, 0.94) with 50% aqueous methanol; and importantly, under these conditions, log k shows even better correlation (r, 0.99) with log P(oct). Effects of residual silanols on HPLC retention with C18 stationary phases were examined. The results show that, in the presence of a small quantity of accessible silanols, the use of 50% aqueous methanol (M50) as eluent yields values of log k directly proportional to log P(oct) in accord with our earlier proposal that use of log k(M50) provides a convenient means for rapid estimation and prediction of log P(oct).
Yamagami
Chisako
C
Kobe Pharmaceutical University, Kobe, Japan. yamagami@kobepharma-u.ac.jp
Kawase
Kaname
K
Iwaki
Kyoko
K
D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005544:Forecasting; D057927:Hydrophobic and Hydrophilic Interactions; D000432:Methanol / Q000737:chemistry*; D008956:Models, Chemical; D000442:Octanols / Q000737:chemistry*; D011719:Pyrazines / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
D000442:Octanols; D011719:Pyrazines; D014867:Water; D000432:Methanol