Note: Descriptions are shown in the official language in which they were submitted.
107~;966
SOLUTE TRANSFER TECHN_QUE
This invention relates to the transfer of a solute
from a first to a second liquid solvent, utillzing a membrane
selectively permeable by gas and impermeable to such liquids.
It :lncludes the steps of flowing the first liquid along the
membrane, evaporating the first liquid across the membrane to
leave a residue from the solute and flowing the second liquid along
the membrane for dissolving therein the residue. Heretofore it
has been common to transfer a substance across a membrane from a
donor stream to a recipient stream as in dialysis. The transferred
substance tends toreach equilibrium across the membrane in such
a dialysis process.
It is known to employ in dialysis a bundle of dialysis
tubes which bundle is interposed in a sleeve such that the dialysate
passing through a wall of the hollow tubing is conveyed away in
the sleeve in which a recipient stream flows. It i8 also known,
in solvent extraction techniques, that a sample in a solvent may
be extracted into a smaller volume of a second solvent in which
some concentration of the sample may occur. However, neither of
these techniques involves evaporation of the first solvent. The
present invention may include, as previously indicated, the evaporation step to
leave the former solute as a residue on the membrane,:and flowing the second
llquid along the membrane for dissolving therein the residue.
It is an object of the invention to provide an improved
method and apparatus for solvent transfer.
In one particular aspect the present invention provides
a method of transferring a solute from a first solvent to a second
but different solvent, said method comprising the steps of: (a)
flowing a first solvent containing a solute along a selectively
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permeable tubular membrane being selective between said first
solvent and said solute, and also between said first solvent and
a second solvent; (b) evaporating said first solvent from said
selectively permeable tubular membrane during flow along said
tubular membrane to obtain a residue of solute within said tubular
membrane; (c) flowing a second solvent different from said first
solvent along said selectively permeable tubular membrane for
dissolving said solute residue to form an effluent; and (d)
analyzing said effluent.
In another particular aspect the present invention provides
apparatus for transferring a solute from a first solvent to a
second solvent, comprising: a selectively permeable tubular membrane
said membrane being impermeable to said solute and to said second
solvent, first means flowing said first solvent along said membrane
for evaporation to dryness of said first solvent across said
membrane to leave a residue of all of said solute along an inner
surface of said membrane, second means for flowing said second
solvent along said tubular membrane to dissolve said residue, and
analyzing means for analyzing said second solvent containing said
solute residue.
In a further particular aspect the present invention provides
apparatus for transferring a solute from a first solvent to a
second solvent along a tubular membrane comprising: a tubular
membrane impermeable to said solute and said second solvent and
selectively permeable to said first solvent, and means for flowing
said first solvent along with said second solvent along said
membrane for evaporation of said first solvent across said
membrane to dryness.
Further objects of the invention will be apparent from the
following detailed description of the invention.
In the drawing:
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10~f~966
Fig. 1 is a somewhat schematic fragmentary view illustrat-
ing apparatus embod~ing the invention;
Fig. 2 is an enlarged view taken on line 2-2 of Fig. li
Fig. 3 is a view similar to Fig. 1 illustrating modified
form and showing a fluid stream flowing through apparatus; and
Fig. 4 is a fragmentary view illustrating a different fluid
stream flowing through the apparatus.
As shown in Fig. 1, compressible pump tubes 10, 12 and
14 extend through a peristaltic pump 20. The pump tube 10 has an
inlet connected to a nonillustrated source of a first solvent
liquid. The inlet end of pump tube 12 is open to the ambient
air for the supply of air to the tube 12. The inlet end of tube
14 is coupled in a nonillustrated manner to a source of a second
solvent. The first solvent has a solute therein whi~h it is
desired to transfer therefrom to the second solvent. The tubes
12 and 14 are coupled to the tube 10 downstream from the pump 20
in the illustrated manner. Thus, the continuous operation of the
pump 20 effects flowing segments of the first solvent which segments
are designated Sl and flowing segments of air, designated A, brack-
eting each segment Sl in the tube 10. A pair of air segments A
also bracket each segment of the second solvent, which last-
mentioned segments are designated S2, flowing in tube 10. The out-
put of tube 10 flows along a membrane which is shown structured as
a tube 16 having an inlet coupled to the outlet of tube 10. The
tube 16 may be formed of silicone, for example, and is selectively
permeable by a gas, but not air, and impermeable by the first and
second liquid solvents. The outlet of the tube 16 is coupled to the
inlet of tube 18 which may be structured of glass, and it is to be
understood that the tubes 10 and 18 are not permeable by gas or
liquids. The outlet of tube 18 may be coupled to an analyzer 40.
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107~9~6
The aforementioned supply of the first solvent liquid may
be from a conventional sampler. The sample may be a fat-soluble
vitamin, such as vitamin A or vitamin D, and the first solvent may
be hexane while the second solvent may be methanol or water. The
ultimate analysis of the sample by analyzer 40 may be by ultra-
violet spectrophotometer or by colorimetèr for example. As in-
dicated in Fig. 1 the first solvent segments Sl containing the
solute flow along the tube 16 in such manner that, at the inter-
face of these segments with the tube 16, segments Sl vaporize with
the gas passing through the membrane or tube 16 to the ambient
atmosphere. In this manner, the segments Sl become progressively
smaller as they flow along the tube 16 to the extent that such
segments disappear leaving a nonillustrated residue of the former
solute on the membrane or tubing wall. The segments S2 of the
second solvent dissolve such residue and the segments S2 flow
from the tube 16 to the tube 18 as previously described. Other
examples of the first solvent are pentane, chloroform, heptane,
tetrahydrofuran, benzene and ethyl acetate. Such solvents evap-
orate through the membrane of tube 16. It will be evident from
the foregoing that the solute in the first solvent must be soluble
in the second solvent in such a solute transfer technique.
~igs. 3 and 4 illustrate a modified form of the invention
wherein glass tubes 22, 26 have their respective inlet ends
coupled to sources of first and second solvents, respectively, and
have their outlet ends connected to a three way valve 24. A solute
is present in the first solvent. The valve has an output along
glass tube 28 which has an inlet end coupled to the valve 24. A
tube 30 has an end exposed to ambient air and an end connected to
the tube 28. Selectively operated pumps 32 are interposed in the
tubes 22, 28 and 30, respectively. The tube 28 has an outlet
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~0'7~9~6
coupled to the inlet of a silicone tube or the like, indicated at
34, of the type similar to the previously-described tube 16. The
outlet end of the tube 34 is coupled to an inlet of a glass tube
36, the outlet of which may be coupled to analyzer 40. The afore-
mentioned construction of the apparatus of Figs. 3 and 4 is such
that the valve 24 may be opened for passage therethrough of either
the first solvent, containing the solute, or the second solvent.
In Fig. 3, there is shown the passage through the last-mentioned
apparatus of the first solvent wherein air delivered from the tube
30 into the tube 28 segments the first solvent, with the pumps 32
interposed in the tubes 22, 30 in operation. The first solvent is
progressively evaporated, passing ~hrough the tube 34 in a manner
previously described with reference to the apparatus in Fig. 1.
However, if desired, the evaporation may be short of dryness. The
evaporation may be such as to only concentrate the solute in the
first solvént for later preparatory use or analysis in analyzer 40
on exit from the tube 36. In the form of Fig. 3, the first solvent
may be completely evaporated to leave the solute as a nonillustrated
residue on the internal wall structure of tube 34, with the air
segments combining and flowing off through the tube 36. Subsequent
to complete evaporation of the first solvent segments Sl the valve
24 is operated to place tube 26 in communication with the tube 34
for the flow of the second solvent segments S2 through the tube 34
as shown in Fig. 4. The pumps 32 interposed in the tubes 26, 30
are operated, with the pump 32 interposed in the tube 22 shut down.
The second solvent segments S2 dissolve the residue of the former
solute on the in~ernal wall structure of the tube 34 to convey the
solute through the tube 36. The apparatus of Fig. 3 is particularly
well suited to receive through the tube 22 an e~fluent stream from
a chromotography column but in no way is limited to such use.
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1076966
If desired, the first solvent may ~e mixed with a third
solvent which may not evaporate through the membrane or tube 34.
In such case, an evaporation of the first solvent, the solute is
concentrated ln the third solvent.
While several forms of the invention have been illustrated
and described, it will be apparent, especially to those versed
in the art, that the invention ma~ take other forms and is
susceptible to various changes in details without departing from
the principles of the invention.
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