Centrifugal partition chromatography (CPC): Emerging separation and purification technique for lipid and related compounds

Centrifugal partition chromatography (CPC), pioneered by Ito in 1964, is a liquid–liquid chromatography without a sorbent, requiring two immiscible solvent phases. This is basically an outgrowth of countercurrent distribution, as developed by Craig and Post (1). In the most distinct variant of CPC, one liquid phase remains stationary while the second solvent phase passes through the stationary phase solvent. The principle of separation involves the partition of a solute between two immiscible solvents (mobile and stationary phases). The relative proportion of solute passing into each of the two solvent phases is determined by the respective partition coefficients. As a liquid– liquid separation technique, CPC offers distinct advantages for the separation, isolation, and purification of lipids such as fatty acids or their derivatives, phospholipids, and tocopherols compared to traditional liquid–solid separation methods, as exemplified by normal column chromatography and/or high-performance liquid chromatography (HPLC). CPC does not require the use of solid support as the stationary phase. Therefore, the possibility of irreversible retention of highly retentive sample components is eliminated. The chromatographer is virtually assured of almost 100% recovery of the compounds from the system for this reason. Any two-phase solvent system may be used; many partition systems can be prepared with nontoxic commonly available solvents. The volume ratio of the stationary phase to the total column (rotor) volume is greater in CPC than in conventional liquid chromatography. Therefore, large quantities of sample materials can be retained in the stationary phase. Decomposition of valuable sample components such as polyunsaturated fatty acids, often encountered in using conventional packed chromatographic columns, is virtually nonexistent under the mild operating conditions used in CPC. Further advantages of CPC are the low solvent consumption and the fact that the same solvent pair can be used for reversed-phase elution. CPC can readily be adapted for large-scale continuous separations. The entire process is performed in the liquid phases, in a closed system. Environmental problems are minimal, and solvent may be completely recovered and recycled.