Toroidal coil counter-current chromatography. Achievement of high resolution by optimizing flow-rate, rotation speed, sample volume and tube length.

This paper deals with optimization of a new seal-free compact toroidal coil centrifuge to achieve high resolution in analytical counter-current chromatography (CCC). Toroidal coil CCC (hydrostatic motion) has advantages compared with high-speed CCC (efficiently mixing solution with planetary motion) in the separation of protein or easily emulsified samples. A toroidal coil separation column of 0.4 mm I.D. PTFE tubing was accommodated around the periphery of the cylindrical centrifuge bowl. Using a two-phase solvent system composed of chloroform-acetic acid-0.1 M hydrochloric acid (2:2:1, v/v/v) and a set of dinitrophenyl-amino acids as test samples, a series of experiments was performed with parameters such as the column length, sample volume, flow-rate, elution mode of the mobile phase and rotation speed. The highest efficiency, over 10,000 theoretical plates, was achieved with a 100 m long coiled tube and an 11 ml total capacity at a flow-rate of 0.01 ml/min at 800 rpm.