High-Speed Countercurrent Chromatography

From TheLiquidPhase

High-Speed Countercurrent Chromatography (HSCCC) instruments are a modern and popular type of Countercurrent Chromatography (CCC) apparatus. These machines consist of:

1. Helically coiled inert tubing (Usually Teflon or sometimes stainless steel) that rotates on its own axis
2. A gear assembly arranged such that the helical coils revolve around a central axis to achieve planetary motion.

In contrast to CPC, there are no rotating seals. HSCCC instruments have a minimum of two orifices. Most modern HSCCC instruments contain multiple (usually two or three) separation coils that can be connected either in series (to give a system with only one inlet and one outlet) or in parallel (multiple inlets/outlets). In practice it is usually most convenient to conect multiple columns in series. This results in a self-balancing system.

Typically, instruments are configured such that one orifice serves as an inlet where the sample and solvents are introduced, and the other as an outlet from which fractions elute. The machine itself is analogous to a Column in HPLC. Unlike HPLC, however, the inlet and outlet tubing may be switched back and forth, depending on whether the heavier (lower phase) or the lighter (upper) phase of the binary system is chosen as the Mobile Phase. (See Solvent Systems)

Several prototype HSCCC instruments have been developed by Ito and manufactured in the NIH machine shop. They differ most notably in the relative angle of the two axes of rotation and in the beta ratio (ratio of central to planetary radii). Machines that have seen most commercial success are of the “J-type” configuration. Extensive and detailed reviews of the various configurations can be found in the books cited below. For a general review, see the volume edited by Ito and Mandava (1988).

As the helical coil rotates about its own axis and revolves around a central axis, an oscillating (hydrodynamic) force field is observed at every given point along the length of the tubing. When filled with a liquid then set in motion, the liquid will migrate towards one of the two orifices, designated the “Head” and away from the other orifice, designated the “Tail”. When the lower phase is chosen as the mobile phase in HSCCC, the instrument is operated in “head-to-tail” mode. The opposite case is called “tail-to-head” elution.

Notes

• Yoichiro Ito and colleagues (NIH, Bethesda, MD) developed planetary, centrifugal CCC
• “Increases gravity” – improves mixing - created hydrodynamic equilibrium
• Theoretically thousands (up to 70,000 per hour) partitioning/chromatographic steps (Mixing, Settling, Separating)

See also

• Instrument Types
• History of CCC

Sources

• Berthod, A, Ed. Countercurrent Chromatography: The support-free liquid stationary phase (Wilson & Wilson's Comprehensive Analytical Chemistry Vol. XXXVIII); Elsevier Science Ltd.: Boston, 2002.
• Conway, Walter D., Ed. Countercurrent Chromatography: Apparatus, Theory and Applications; VCH Publishers: New York, 1990.
• Conway, Walter D.; Petroski, Richard J. Modern Countercurrent Chromatography (ACS Symposium Series #593); ACS Publications, 1995.
• Ito, Yoichiro. Golden rules and pitfalls in selecting optimum conditions for high-speed counter-current chromatography. Journal of Chromatography, A 2005, 1065, 145-168.
• Ito, Yoichiro; Conway, Walter D., Eds. High-speed Countercurrent Chromatography (Chemical Analysis, Vol 132); John Wiley and Sons: New York, 1996.
• Mandava, N. Bhushan; Ito, Yoichiro, Eds. Countercurrent Chromatography: Theory and Practice (Chromatographic Science Series, Vol. 44); Marcel Dekker, Inc.: New York, 1988.
• Menet, Jean-Michel; Thiebaut, Didier, Eds. Countercurrent Chromatography (Chromatographic Science Series Vol 82); Marcel Dekker, Inc.: New York, 1999.