EXTENDED OCTANOL-WATER PARTITION-COEFFICIENT DETERMINATION BY DUAL-MODE CENTRIFUGAL PARTITION CHROMATOGRAPHY

The range of determination of octanol-water partition coefficients by CPC has been extended by the dual-mode approach. In this mode, the analyte was pumped in the descending mode with water as the mobile phase for a predetermined time. The mode was then switched to ascending with octanol as the mobile phase. Lipophilic materials only moved partially through the system in the descending mode. They rapidly eluted in the ascending mode with good signal-to-noise. The partition coefficient was shown to equal the volume of water pumped in the descending mode divided by the retention volume in the octanol phase ascending. A systematic positive error resulted when the experimentally selected descending volume was too small.