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Description  |
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FIELD OF THE INVENTION
This invention relates to continuous countercurrent extraction devices and
to continuous particle separation devices, and more particularly to an
elution method and apparatus for continuous countercurrent chromatography
and blood separation using a rotating coiled tube or conduit in an
acceleration field.
BACKGROUND OF THE INVENTION
Various types of coil planet centrifuges have been developed for separating
solutes and/or particles on the basis of partition coefficients and/or
elutriation. Among the various schemes, the most efficient separations
have been achieved from those utilizing coiled tubes rotating in an
acceleration field of either gravitational or centrifugal origin. Several
schemes to perform continuous countercurrent extraction have been
described, such as employing a flow-through coil planet centrifuge (see
U.S. Pat. No. 4,151,089 to Y. Ito) and inducing a homogeneously
circulating force field around the coiled tube (see U.S. Pat. No.
3,775,309 to Y. Ito et al). A prior art arrangement providing
heterogeneously circulating centrifugal force fields around the coiled
tube, as utilized in the present invention, is exemplified in connection
with the horizontal flow-through coil planet centrifuge disclosed in U.S.
Pat. No. 4,058,460 to Y. Ito, and also in a toroidal coil planet
centrifuge apparatus disclosed in U.S. patent application Ser. No. 45,052,
of Y. Ito. Another system of cell separation and plasmapheresis, relative
to which the present invention is an improvement and simplification, is
disclosed in U.S. patent application Ser. No. 661,114, of Y. Ito,
employing no rotating seals. In this system, however, a large portion of
the flow tubes is subjected to revolution around the central axis of the
apparatus, which limits the applicable centrifugal force field to the
column.
SUMMARY OF THE INVENTION
Accordingly, a main object of the present invention is to overcome the
disadvantages and deficiencies of previously employed continuous
countercurrent extraction and continuous particle separation systems.
A further object of the invention is to provide a novel and improved
elution method and apparatus for continuous countercurrent chromatography
and blood separation using a rotating coiled tube or conduit in an
acceleration field.
A still further object of the invention is to provide an improved
continuous flow-through coil planet centrifuge system for separating
solutes and/or particles on the basis of partition coefficients and/or
elutriation which may utilize coiled tubes or conduit means rotating in an
acceleration field of either gravitational or centrifugal origin, which
avoids the use of rotating seals, which utilizes heterogeneously
circulating centrifugal force fields around a coiled tube or conduit
means, and which can be efficiently and economically employed for
continuous countercurrent chromatography or for blood separation.
A still further object of the invention is to provide a novel and improved
method and apparatus for performing continuous extraction of chemicals and
separation of particles, which includes separation and purification of
isotopes from nuclear wastes, preparative-scale separation of various
chemicals, cell separation, and the like.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects and advantages of the invention will become apparent from
the following description and claims, and from the accompanying drawings,
wherein:
FIG. 1 is a diagrammatic view showing the orientation and motion of a coil
holder undergoing a synchronous planetary motion.
FIG. 2 is a diagram showing the distribution of the relative centrifugal
force fields acting on the various points on coil holders at a given
moment, the diagram illustrating respective coil holders of three
different beta values.
FIG. 3 is a longitudinal vertical cross-sectional view of a typical
horizontal flow-through coil planet centrifuge for continuous
countercurrent extraction according to the present invention.
FIG. 4 is a diagram showing the elution scheme of a helical column for
continuous countercurrent extraction according to the present invention.
FIG. 5 is an enlarged cross-sectional view taken through a three-way
connector and cooperating tubing employed in a typical design of a coil
planet centrifuge according to the present invention to provide the inlet
and outlet connections at each end of the coiled column.
FIG. 6 is a vertical cross-sectional view of a blood cell separation
apparatus according to the present invention.
FIG. 7 is an enlarged top plan view, with its cover removed, of a
separation bowl which may be employed in the apparatus of FIG. 6.
FIG. 8 is a transverse vertical cross-sectional view of the separation
bowl, taken substantially on the line 8--8 of FIG. 7.
FIG. 9 is a top plan view, with its cover removed, of a modified form of
separation bowl which may be employed in the apparatus of FIG. 6.
FIG. 10 is a transverse vertical cross-sectional view taken substantially
on the line 10--10 of FIG. 9.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to the drawings, FIG. 1 diagrammatically shows the orientation
and motion of a cell holder 11 undergoing a synchronous planetary motion.
The holder revolves around the axis of revolution and simultaneously
rotates about the axis of rotation, or its own axis, at the same angular
velocity .omega. in the same direction. A bundle of flow tubes 12 from the
holder, supported tightly at a point on the axis of revolution, as
illustrated, becomes free of twisting under this particular mode of the
planetary motion of the holder. Acceleration acting on an arbitrary point
P on the holder located at a distance r from the axis of rotation has been
analyzed. FIG. 2 shows a distribution of the relative centrifugal force
fields acting on the various points on the holder at a given moment, where
beta (.beta.) denotes r/R, and O and Q denote the axis of revolution and
the axis of rotation respectively. As is clearly illustrated, the
centrifugal force vector is always directed outwardly substantially
radially from the axis of rotation when the beta value is greater than
0.25, and is also heterogeneous in all directions. At a given beta value,
the arbitrary point P on the holder rotates around point Q with respect to
this force distribution pattern and, therefore, it experiences these
fields in order during one revolutional cycle. When a tube is coiled
around the holder coaxially, a particle present in the coil will travel
toward one end of the coil, and this end is called the "head", while the
other end is called the "tail" of the coil.
The hydrodynamic motion of the two immiscible solvent phases enclosed in
such a coil is quite complex, but is easily studied by actual experiment.
The results of such experiments show that in most of the cases the two
phases are soon completely separated along the length of the coil. One
phase occupies the head end and the other occupies the tail end of the
coil. A series of experiments has been performed to determine which phase
comes to the head end. The results suggest that the less viscous and
lighter phase advances toward the head end of the coil. Some typical
examples are listed below:
______________________________________
Two-phase solvent system
Head Tail
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Hexane/H.sub.2 O
upper nonaqueous
lower aqueous
Ethylacetate/H.sub.2 O
upper nonaqueous
lower aqueous
n-Butyl alcohol/H.sub.2 O
lower aqueous
upper nonaqueous
Blood Red cells Plasma
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Thus, when blood is introduced into the coil, red cells advance toward the
head, and the plasma is separated at the tail end of the coil.
The separations of the two phases and/or cells are further accelerated by
modifying the coiled column configuration into a spiral form. In this
case, the heavier component tends to travel toward the larger diameter end
and the lighter component tends to travel toward the smaller diameter end
of the spiral column. Therefore, the head and tail relationship of the
spiral column should be determined such that the separation of two phases
or cells is promoted. For example, for the hexane/water phase system the
head end should be the smaller diameter end of the spiral column, while
for the blood cell separation the head end should be the larger diameter
end of the spiral column.
FIG. 3 shows a horizontal flow-through centrifuge for continuous
countercurrent extraction according to the present invention, designated
generally at 13. In said centrifuge 13, a motor 14 drives a rotary frame
consisting of a pair of rotary wings 15, 16 rigidly connected by a
plurality of spaced links 17. Said frame is mounted to rotate around a
stationary horizontal pipe 18, forming the central axis of the apparatus.
The frame supports a pair of rotary shafts 19a, 19b, each equipped with a
planetary gear 20 at one end. Each planetary gear 20 is in mesh with an
identical stationary sun gear 21 rigidly mounted on the central stationary
pipe 18. This gear arrangement causes each rotary shaft 19a, 19b to
undergo a synchronous planetary motion, i.e., revolution around the
central axis of the apparatus and rotation about its own axis at the same
angular velocity .omega. and in the same direction, as illustrated in FIG.
1. Each column is prepared by winding a tube coaxially around a respective
rotary shaft, and may be either of helical or spiral configuration. In
FIG. 3 said tubes, shown at 22, are of helical configuration. The flow
tubes from the rotary shaft 19a, forming a bundle 23a, are first led
through an axial passage 24a of rotary shaft 19a, and then enter the bore
25 of stationary pipe 18 via a side opening 26 of a short coupling pipe 27
rigidly secured to the frame rotary wing 15 in axial alignment with the
left end of stationary pipe 18, as viewed in FIG. 3. The flow tube bundle
23b from the rotary shaft 19b is similarly led through an axial passage
24b, through a pair of holes 26 in rotary wings 16 and 15, through another
side hole 28 in coupling pipe 27, and through a stationary axial support
tube 29 rigidly secured to a vertical fixed side member 30 forming part of
the stationary supporting structure of the apparatus. The holes 26 are
located some distance away from the location of gears 20 and 21. In this
way, the flow tubes from each rotary shaft 19a, 19b are allowed to rotate
freely without interference or twisting. The design shown in FIG. 3 allows
simultaneous operation of two columns. However, when only a single column
is to be used, a suitable counterweight should be mounted on the other
column holder to balance the centrifuge.
FIG. 4 schematically illustrates the elution scheme of a helical column of
FIG. 3 arranged for continuous countercurrent extraction. When two
immiscible solvent phases A and B are confined in the coiled tube 22, the
rotation of the coil separates the two phases in such a way that one
phase, A, accumulates in the head end of the coil and the other, B,
accumulates in the tail end. Under these circumstances, phase A, eluted
through the tail end of the coil, can be collected through the head end,
while phase B, eluted through the head end, can be collected through the
tail end of the coil. The two phases thus undergo a countercurrent flow in
the coil, and samples introduced through a sample feed tube connected to
the middle portion of the coil are separated according to their partition
coefficients. The solutes in the sample solution may be eluted from the
head end of the coil when the values of their partition coefficients favor
the phase A, may be eluted through the tail end when the values of the
partition coefficients favor the phase B, or may be retained in the coil
when the partition coefficients fall between the above phase-favoring
values. To meet these requirements, the coiled tube is equipped with five
flow tubes, as follows:
flow tube I.sub.head : feed tube for phase B, located at the head end,
flow tube O.sub.head : return tube for phase A, located at the head end,
flow tube I.sub.tail : feed tube for phase A, located at the tail end,
flow tube O.sub.tail : return tube for phase B, located at the tail end,
flow tube I.sub.sample : sample feed tube located at the middle portion of
the coil.
In each operation the coil is first filled with either phase or a mixture
of both phases, followed by elution of both phases through the respective
inlet tubes I.sub.head and I.sub.tail, while the apparatus is rotated at
the optimum revolutional rate. After the steady state hydrodynamic
equilibrium is established in the coil, the sample solution is fed through
the flow tube I.sub.sample at a constant rate. When the operation is aimed
at enrichment and/or stripping of a particular substance or substances,
the flow tube I.sub.sample may not be used, and instead the sample
solution is directly introduced through I.sub.head or I.sub.tail, while
the enriched or stripped solution is continuously collected through either
O.sub.head or O.sub.tail.
FIG. 5 illustrates a typical design of a combined inlet and outlet
connector assembly employed at each end of the helical column. This
assembly comprises a three-way connector body 31 of suitable inert
material, such as Kel-F, polyethylene, or the like, connected to the end
of the coil 22. The body 31 is formed with a longitudinal main bore 32 and
a perpendicularly directed passage 33 communicatively connected to the
intermediate portion of said main bore 32. An outlet tube 34 is connected
to passage 33 by means of a conventional externally threaded flanged
bushing 35 engaged is an internally threaded recess 36 coaxial with and
aligned with passage 33. A similar flanged bushing 37 communicatively
connects the end of coil 22 to body 31 in an internally threaded recess 38
coaxial with and aligned with main bore 32 at one end of body 31. An inlet
tube 39 is communicatively connected to the other end of main bore 32 by
another flanged bushing 40 engaged in an internally threaded recess 41. A
relatively fine tube 42 of suitable inert plastic material is tightly
received in the inlet tube 39 and extends into the coiled column tube 22
for a substantial distance, as shown. This arrangement not only simplifies
the design of the column but also eliminates undesirable backflow through
the outlet tube 34 of the solvent introduced from the inlet tube 39.
Blood cell separation necessitates a relatively strong centrifugal force
field compared with that required for continuous countercurrent
extraction. Therefore, the design of a centrifuge for this purpose should
be made so as to tolerate a strong force acting on the separation bowl.
The stability and durability of the centrifuge system can be greatly
increased by shortening the rotary shaft and placing it in a vertical
position, as in the case of an ordinary centrifuge.
FIG. 6 shows a typical design of a blood cell separator according to the
present invention. The blood cell centrifuge of FIG. 6 is designated
generally at 43, and its mechanism is mounted between a pair of vertically
spaced, stationary horizontal support plates 44, 45. A vertical motor 46,
rigidly secured to bottom plate 45, drives a rotary frame 47, via a short
coupling pipe 57, around a vertical stationary pipe 48 rigidly secured to
and depending from the stationary top plate 44. The rotary frame 47
comprises two spaced horizontal plates 49, 50 rigidly linked together, and
an additional horizontal plate 51 spaced above and connected to plate 49,
serving as a support for a vertical hollow rotary shaft 52, which in turn
supports a horizontal centrifuge bowl 53 secured on said shaft 52. The
shaft 52 is provided with a planetary gear 54 which meshes with an
identical stationary sun gear 55 rigidly secured on the stationary
vertical pipe 48. This arrangement provides the desired planetary motion
of the separation bowl 53, namely, revolution around the central axis of
the centrifuge and rotation about its own axis at the same angular
velocity, and in the same direction. Bowl 53 is provided with a suitable
detachable top cover 85.
The flow tubes from the separation bowl 53, shown as a bundle 56, are
passed downwardly through the central bore of the hollow shaft 52, extend
through a hole 58 in coupling pipe 57, and then extend upwardly through
the bore of the stationary bearing pipe 48, thereby exiting from the top
of the centrifuge.
A suitable counterweight 59 is connected between plates 51, 49
diametrically opposite bowl 53.
FIGS. 7 and 8 show a typical example of a design for the separation bowl
53. Said bowl 53 may comprise an aluminum, generally disc-shaped body 60
formed with upstanding concentric inner and outer annular flanges 61 and
62, defining an annular groove 63 therebetween. A pair of identical
thin-walled spiral channel tubes 64,64, which may be of rectangular
cross-sectional shape, are symmetrically and concentrically arranged in
the annular groove 63, and the remainder of the space in said groove is
filled with a light-weight rigid plastic material or plastic foam, shown
at 65.
The number of spiral channels can be increased by spacing extra channels
symmetrically around the periphery of the bowl. As shown in FIGS. 9 and
10, such multiple channels can be made directly in the solid aluminum bowl
without the use of the plastic spacer material 65, with the advantage of
reduced weight of the bowl and increased strength by using the integral
metal channels. Thus, in FIGS. 9 and 10, the separation bowl is designated
generally at 66, and comprises an annular aluminum bowl 67 integrally
formed with four 90.degree.-spaced concentric identical spiral channels
68. The bowl has a peripheral flange 69 to which a suitable top cover 85
may be secured. This design inherently provides increased strength to
support the channels, which is desirable because of the very strong
centrifugal force field.
As is diagrammatically shown in FIG. 7, during the continuous centrifugal
cell separation process the blood sample is admitted via a supply tube 70
to the intermediate portion of a separation channel 64 (or 68). The red
blood cells leave via an outlet tube 72 from the large-diameter end of the
separation channel. The plasma leaves via an outlet tube 73 from the
small-diameter end of the channel.
It will be seen that FIG. 4 diagrammatically illustrates a flow-through
system covering both the helically coiled column arrangement of FIG. 3 and
the spirally coiled column arrangements of FIGS. 7 and 9. In FIG. 4, the
first phase (phase A) feed conduit means 80 (I.sub.head) is connected to
the column at a coil element adjacent to the head end, and a second phase
(phase B) conduit means 81 (I.sub.tail) is connected to the column at a
coil element adjacent to the tail end. Second phase collection conduit
means 82 (for collecting phase B, shown at O.sub.head) is connected to the
column at a coil element adjacent to the head end, and first phase
collection conduit means 83 (for collecting phase A, shown at O.sub.tail)
is connected to the column at a coil element adjacent to the tail end. A
sample-admission conduit means 84 (at I.sub.sample) is connected to a coil
element 86 at the middle portion of the column. As above mentioned, the
separable substances in the sample may be eluted from the head end at
conduit 82 of the column when the values of their partition coefficients
favor phase A, or may be eluted from the tail end of the column at conduit
83 when the values of their partition coefficient favor phase B.
While specific embodiments of an improved apparatus and method for
continuous countercurrent extraction and particle separation have been
disclosed in the foregoing description, it will be understood that various
modifications within the scope of the invention may occur to those skilled
in the art. Therefore it is intended that adaptations and modifications
should and are intended to be comprehended within the meaning and range of
equivalents of the disclosed embodiments.
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