CLASSIFICATION OF COUNTERCURRENT CHROMATOGRAPHY SOLVENT SYSTEMS ON THE BASIS OF THE CAPILLARY WAVELENGTH

Solvent systems used for countercurrent chromatography (CCC) have been classified in three groups, defined by Ito from experimental observat ions of their flow behaviors in a countercurrent chromatograph. To ach ieve good retention of one phase of a solvent system when the other on e is pumped in the column, it is necessary to know to which of these g roups it belongs. As the physics of the interface of biphasic liquid/l iquid systems is governed by the capillary wavelength, one expects the latter to be a key parameter for partly describing the two-phase flow inside a CCC column. Parameters derived from the capillary wavelength , the characteristic settling velocities, can also be calculated from the physicochemical properties of the phases and their interfacial ten sion. Their values are utilized for classification purposes and applie d to previously investigated solvent systems as well as six new system s used in CCC. The classification obtained is compared with that provi ded by the observed flow behavior. It is found that the classification based on the characteristic settling velocity of the lighter phase in to the continuous heavier one provides a reasonably reliable predictio n of the experimental flow behavior in CCC.