Development of a new preparative spiral-coil low-speed rotary countercurrent chromatographic (spiral-coil LSRCCC) method

A new prototype, large-scale countercurrent chromatograph was constructed. It was equipped, with a three-layer spiral column made from a continuous piece of convoluted Teflon tubing (8.5 mm I.D. and 9.7 m in length), which was accommodated in a spirally carved foam plastic holder. Two different types of two-phase solvent systems were used to evaluate stationary phase retention and mixing effect between stationary and mobile phases, i.e., chloroform/water (1 : 1, v/v) for separation of caffeine and theophylline; and 1-butanol/acetic acid/water (4: 1 : 5, v/v/v) for separation of dipeptides, valyl-tyrosine (val-tyr), and tryptophyl-tyrosine (trp-tyr). A set of different elution modes (inside-outside and head-tail), and rotational speed (0-400 rpm) was assessed for stationary phase retention and separation efficiency. The elution mode of inside to outside of the spiral for the lower mobile phase or the opposite direction for the upper mobile phase, is rated the best for stationary phase retention due to observed spiral effect for liquid movement. Different operational parameters, such as rpm and flow rate of the mobile phase were evaluated for separation efficiency and speed. The obtained data revealed that the spiral effect and Archimedean screw force were two important contributing factors for yielding the enhanced speed and higher partition efficiency, compared to conventional low-speed rotary countercurrent chromatography.