Two immiscible liquids of different density, filling a closed helical tube, become distributed into a pattern of alternating segments when the tube is rotated on its axis, perpendicular to a gravitational field. A solute loaded at the initial single liquid-liquid interface will become distributed in segments of each liquid along the coil according to its partition coefficient. Using centrifugal force instead of gravity, this principle has been applied to develop a countercurrent system on an unprecedented small scale. With the equipment developed, 12 samples of microgram quantities of material can be subjected to countercurrent separation, each in a total volume of about 0.5 ml of solvents, in about 5 hours. The factors affecting efficiency have been analyzed and improvements in resolution can be expected. The resolving power of this method increases (1) in proportion to the number of turns of the coil (coil units), (2) inversely with the internal diameter of the tube, and (3) in proportion nearly to the square root of time required to complete the segmentation of the two solvents along the length of the tube. With the apparatus in use and 6 meters of plastic capillary tubing coiled as 300 turns, the resolving power is equivalent to 300 “theoretical plates.” Preliminary experiments were performed to demonstrate separation of basic dyes, algal proteins, and erythrocytes. © 1969, American Chemical Society. All rights reserved.
