Separation with Multi-Layer Coil Counter-Current Chromatography (MLCCC)

Abstract

Counter-current chromatography (CCC) is a low-pressure, all-liquid chromatographic technique which requires no solid support. [ 1 ] Commonly it utilizes two immiscible solvent phases plus an auxiliary solvent which is miscible in both phases. The mobile phase is pumped through the stationary phase, causing the compounds to partition between two immiscible solvents, based on the partition coefficients of the solutes. MLCCC is an advanced form of CCC and employs teflon tubing wound onto a bobbin, which is centrifugally rotated in a planetary fashion [ 2 ] (Fig. 1). The planetary motion sets up alternating zones of mixing and settling which travel along the length of the coil and result in the partitioning of the components. The main advantages of CCC over conventional chromatography techniques are the absence of a solid support, the use of inexpensive solvents, and complete recovery of highly functional and reactive compounds. In contrast to other forms of CCC, MLCCC can be used on both an analytical and preparative scale. Due to high centrifugal forces, an increase in the number oftheoretical plates is achieved, thereby allowing up to 50000 mixing zones to occur per hour. This results in efficient partitioning and separation of the components in a complex mixture. Hence MLCCC is beginning to be more widely accepted as a method of choice for the separation and isolation of highly polar natural products.