Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev

13 COUNTER-CURRENT CHROMATOGRAPHY
along the length of the tube where the lighter phase occupies one end (called
the head) and the heavier phase occupies the other end (called the tail).
Although the cause of this bilateral hydrodynamic phase distribution of two
immiscible solvents is still unknown, it can be effi ciently used for performing
CCC. In Figure 5A the coil at the top shows bilateral hydrodynamic distribution
of the two phases in the coil where the white phase (head phase) occupies
the head half and the black phase (tail phase) the tail half.
This condition clearly indicates that the white phase introduced
at the tail end will move toward the head and similarly the black phase introduced
at the head will move toward the tail. This hydrodynamic trend is
effectively used for performing CCC (Figure 5B). The coil is fi rst entirely fi lled
with the white phase followed by pumping the black phase from the head
end (Figure 5B, top). Similarly, the coil is fi lled with the black phase followed
by pumping the white phase from the tail (Figure 5B, bottom). In either case,
the mobile phase quickly moves through the coil, leaving a large volume of
the other phase stationary in the coil.
A
Bilateral Hydrodynamic Equilibrium
in a Closed Coil
Head
B
Tail
One-Way Elution Modes
Flow
Head
Tail
Figure 5: Mechanism of HSCCC. (A) Bilateral hydrodynamic distribution of two phases
in the coiled column. (B) Elution mode of both lighter and heavier phases through the
rotating coiled column.
• The motion and distribution of the two phases in the rotating
coil were observed under stroboscopic illumination, and are
illustrated in Figure 6A.
• A spiral column undergoes type-J planetary motion. The area
in the spiral column is divided into two zones: the mixing zone
occupying about one-quarter of the area near the center of
revolution and the settling zone in the rest of the area.
• In Figure 6B, the spiral column is stretched and arranged
according to the positions I–IV to visualize the motion of the
mixing zones along the tubing.
• Each mixing zone travels through the spiral column at a rate
of one round per revolution.
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