Ph-zone-refining countercurrent chromatography

Abstract

It has now been discovered that acidic or basic compounds may be purified using a new countercurrent chromatography technique. This technique utilizes two immiscible solvent phases, one being acidic and one being basic. The solutes partition between the phases and elute in contiguous, well-resolved, rectangularly shaped peaks in order of their partition coefficients. The fractions within any single peak have a substantially constant concentration. In addition to differing partition coefficients, the peaks also differ in pH, successively increasing in the case of a basic mobile phase and successively decreasing in the case of an acidic mobile phase. For this reason, the technique may be referred to as 'pH-zone-refining countercurrent chromatography.' The method of this invention provides certain advantages over previously known countercurrent chromatography techniques. First, the method permits one to load a sample as a suspension into the separation column. Additionally, the minimal degree of elution peak overlap permits one to separate mixtures of greater volume than before in any given column without loss of resolution. Thus, columns which are otherwise recommended for separations of mixtures up to a certain maximum size can be used in the method of this invention for separating mixtures up to ten times that size or greater.