U.S. patent number 3,640,822 [Application Number 04/857,956] was granted by the patent office on 1972-02-08 for method and an apparatus for separating a segmentation medium from a stream of a segmented main fluid.
This patent grant is currently assigned to Ceskoslovenska akademie. Invention is credited to Jiri Hrdina.
United States Patent |
3,640,822 |
Hrdina |
February 8, 1972 |
METHOD AND AN APPARATUS FOR SEPARATING A SEGMENTATION MEDIUM FROM A
STREAM OF A SEGMENTED MAIN FLUID
Abstract
Segmented main fluid in a capillary stream is allowed to flow
through a main tubing equipped with a capillary slot communicating
with an offtake pipe. Conditions within the apparatus are
maintained such that capillary forces and surface tension inherent
in the elements of the segmentation medium and other parts of the
system prevent their passage through the capillary slot, through
which the main fluid only is taken off in a continuous stream. The
length of the capillary slot in the direction of the main capillary
tubing axis exceeds the maximum contact length of a segmentation
medium element; the main fluid may be taken off substantially from
a single one only, or from not more than two neighboring segments
of the main medium, so that contamination by the contents of other
segments is negligible. BACKGROUND OF THE INVENTION 1. Field of the
Invention The present invention relates to a method of and an
apparatus for removing a segmentation medium from a segmented
stream of a main fluid. A segmented stream is produced by dividing
a main fluid passing through a tubing into individual segments,
which are separated from one another by so-called segmentation
elements, consisting either of bubbles or drops of so-called
segmentation medium, which is substantially immiscible with the
main fluid. It is a known measure in the art to convert a
continuous stream of a main fluid to be treated in a desired
manner, e.g., measured, analyzed etc., into a segmented stream;
considerable advantages are thereby achieved, if the stream of the
fluid has to be passed through various appliances, such as
analyzers comprising capillary reactors, dialyzers connecting tubes
and the like. The segmentation elements are highly effective in
preventing the intermingling of various segments of the main fluid,
which usually contain different substances, such as samples--
originally fully separated from one another-- to be successively
analyzed in automatic analyzers. A segmented stream can further be
used in processes, where a reduction of concentration gradients of
various substances is to be obviated. This is the case for instance
in chromatography, where various substances are conveyed by a
stream of an eluent discharged from a chromatographic column, after
they have been separated in the latter. The stream, entraining the
various separated components of the original mixture (e.g., after
the above-mentioned chromatographic separation), is passed through
a number of appliances, such as capillary reactors, in which the
reaction capillary has a considerable length in order to provide
for the required period of reaction, further through a variety of
hydraulic switches, mixers, connecting tubes etc. It is a great
advantage, in particular in connection with automatic analyzers,
that the segmentation elements efficiently prevent the
intermingling of the fluid contained in the individual segments of
the segmented stream, even if the fluid is passed through numerous
appliances along a relatively long path. Before the main fluid is
fed into the measuring or other treating apparatus, it has, as a
rule, to be free from the segmentation medium, which, if admitted
to the measuring or other apparatus (such as a flow photometer,
colorimeter, flow conductometer etc.), would interfere with its
operation. The segmentation medium may consist of a gas, such as
air, nitrogen or the like, and in this case the segmentation
elements are constituted by gas bubbles or it may consist of
mercury, oil or the like, in which case the segmentation elements
consist of drops of a segmentation medium. With a view to the fact
that the invention enables the use of any desired segmentation
medium, either gaseous or liquid, the term "segmentation elements"
will throughout this disclosure denote bubbles of gas as well as
drops of liquid. 2. Description of the Prior Art Devices have
previously been proposed for use in separating a segmenting medium
from a stream of main fluid. In the majority of such known devices
gas is used as the segmentation medium and as gas bubbles have to
be removed from the main fluid stream, such devices have been
called "debubblers." The heretofore known and used debubblers
consist usually of a straight main tube or of a tube relatively
sharply bent at the debubbling point, said main tube communicating
with a branch line serving for the withdrawal of the main fluid,
freed from bubbles. The branch line opens into the (sharply) bent
or straight portion of the main tube by a funnel-shaped enlarged
space, having a relatively large volume. The cross-sectional area
by which the funnel-shaped space opens into the main tube has
usually substantially equal longitudinal and transverse dimensions,
which as to their order correspond approximately to the inner
diameter of the main tube. Having reached this funnel-shaped space,
the gas bubble finds here sufficient room to assume a shape
determined substantially by its surface tension only, so that it
can assume approximately a spherical shape (naturally slightly
deformed by outer influences to which it is subject at this point).
The bubble thus sets partially free the flow of the main fluid into
the branch line, not only from the main fluid segment lying beyond
the bubble, but also in front of the bubble. If, under these
circumstances, a reliable separating effect is to be achieved, in
order to remove the segmentation medium, the total through-flow
profile at the point where the branch line opens into the main
tube, must have such a size that the segmentation element (bubble),
when passing through this point, should not close the through-flow
profile at this point not even after it has changed its shape due
to the release of forces, which previously acted thereon; when
passing through this point, the dimension of the bubble in
longitudinal direction is reduced but in transverse direction
increased. The liquid can be taken off continuously from the lower
part of the funnel-shaped space, without the gas bubble penetrating
into the lateral takeoff tube. However these devices show a
considerable disadvantage in that in the relatively large
funnel-shaped space there occurs an intermingling of liquids not
only from two adjacent segments but also from further segments of
the segmented main fluid. In other words, the funnel-shaped space
represents a relatively large pocket, in which an undesirable
mixing of liquids from a plurality of segments takes place. This
results in a highly objectionable reduction of the concentration
gradients in the stream of the main fluid. This is true even in
spite of the fact that such devices are disclosed in various
publications and patent specifications, where they are usually
represented diagrammatically by a lateral tube, branching off from
a main tube at right angles or under an inclination, without said
funnel-shaped separating space being illustrated in the respective
drawings. Such a device without a separating space would, of
course, be inoperative and incapable of achieving a reliable and
perfect separation of the segmentation medium. SUMMARY OF THE
INVENTION The main object of the invention is to provide a method
and an apparatus which are well adapted to effect a reliable
elimination of the segmentation medium from the stream of a
segmented main fluid. Another object is to provide a method and an
apparatus of the aforementioned type, which are adapted to remove
elements of the segmentation medium intervening between the various
segments of the main fluid, while substantially preventing the
intermingling of more than two adjacent segments of the main fluid.
Still another object is to provide a method and an apparatus of the
aforementioned type, which ensure a minimum depreciation of the
concentration gradients in the stream of the main fluid. A further
object of the invention is to provide a method and an apparatus of
the above type, which are universally applicable not only with a
gaseous but also with a liquid segmentation medium. A still further
object is to provide an apparatus capable of operation in any
required position and not only in a substantially vertical
position, as is usual in the heretofore known devices. Another
object is to provide an apparatus of the aforementioned type, which
can be produced without difficulties and at low cost, while
ensuring a high accuracy in operation. A further object is to
provide an apparatus of the aforementioned type, which in
combination with a measuring or other instrument enables a
considerable increase in the accuracy of measurement or other
treatment. Other objects and advantages of the invention will be
understood from the ensuing description of the invention considered
in connection with the accompanying illustrative drawings. The
invention is based on a known phenomenon concerning the surface
tension of a drop or bubble of a medium, surrounded by another
medium with which it does not mix. As known, the surface tension
acts on the drop of liquid in inward direction in such a way, that
if no outer influence were present, the drop would assume
theoretically the smallest volume confined in the surface of equal
curvature i.e., a spherical shape. However, the drop is subject to
outer influences, such as gravity, pressure, wall influence etc.,
which tend to deform it, but this is counteracted by the surface
tension generating a certain resistance. If the drop lies against
an aperture which is smaller than the diameter of the drop and if a
pressure acts on the other side of the drop, the latter does not
enter the aperture, as long as the resistance offered by the
surface tension to the deformation of the drop, exceeds the outer
pressure. The drop will just be more deformed, in dependence on the
increasing outer pressure, and slightly penetrate into the
aperture, but it will not pass through it. Not until the outer
pressure increases to such a value as to overcome the resistance
produced by the surface tension against a deformation of the drop
to a dimension corresponding to the dimension of the aperture, will
the drop be urged into the aperture. The value of the resistance
against deformation (produced by the effect of the surface tension
and capillary forces) at this moment will in the further disclosure
be termed "critical resistance against deformation." The value of
this resistance will depend on the nature of the material of the
drop (and of the materials surrounding the drop), on the ratio
between the drop diameter and the area of the aperture into which
it has to be pressed, on the angle under which it penetrates into
the aperture (the drop will enter easier into a conical aperture
than into an aperture with sharp edges) on the characteristics of
the material in which the aperture is made and in particular on the
contact angle under which the respective meniscus bears on the wall
etc. The value of the resistance may be determined without great
difficulty for any given case. The drop or bubble when flowing
through a tubing contacts the wall of the tubing along a certain
length which likewise depends on outer influences, pressures, etc.
This length will in the following specification be called "contact
length." A further important factor is the affinity between the
segmentation medium and the wall of the tubing, through which the
segmentation medium advances. This affinity depends on the
character of the medium and of the material of the wall of the
tubing and is different for various substances. So is for instance
the affinity between glass and mercury different from the affinity
between glass and water (or oil). This affinity, which plays an
important role in the present invention, will hereinafter be called
"surface affinity of the segmentation medium." The present
invention utilizes the above-disclosed phenomenon for separating
the segmentation medium (either a gas bubble or a drop of liquid)
from the stream of the main fluid. The main inventive idea resides
therein that from the segmented stream of the main fluid a
capillary stream of said fluid is tapped along a path exceeding the
maximum contact length of a segmentation element in the direction
of flow of the segmented stream and this tapped stream, containing
a part of the main fluid is taken off, while the outer influences
acting on the segmentation elements and caused mainly by
hydrostatic and hydrodynamic pressures, pressure difference at the
transition from the main segmented stream, into the tapped stream
and the takeoff pressure of the main fluid are maintained at a
value lower than the critical resistance against deformation of the
segmentation element, exerted by the capillary effects, surface
tension thereof and the surface affinity of the segmentation
medium. As a result, the segmentation element is not forced into
the tapped stream, while a continuous takeoff of the main fluid
from points directly in front of, and behind, the segmentation
element or from a single segment of the main fluid is effected, the
tapped main fluid being completely freed from segmentation
elements, which will advance further with the segmented stream of
the remaining main fluid to the waste or to further use. By a
suitable choice of the length of the tapped stream it may be
achieved that the main fluid is taken off from not more than two
adjacent segments of the main fluid and mostly from not more than
one single segment, which fact contributes exceedingly to an
increased accuracy and reduces the undesirable intermingling and
contamination of different segments of the main fluid. The
capillary tapped stream can be either continuous or may consist of
several partial streams, whose overall length, measured in the
direction of movement of the segmented stream is chosen such as to
ensure the tapping of the main fluid from not more than two
adjacent sections of the segmented main fluid. Sometimes it is not
of primary importance to tap samples of the main fluid from a
single segment or from not more than two neighboring segments,
greater emphasis being placed on a certain degree of smoothing or
levelling the differences in quality of the individual segments or
on a high flow rate of samples withdrawn from the segmented stream.
In these cases the length of the capillary takeoff stream may be
increased so as to extend over more than two segments. The
invention relates equally to an apparatus for effecting the new
method. Such an apparatus comprises a main tubing for the stream of
the segmented main fluid and a branch line for taking off (or
sucking off) the main fluid freed from segmentation elements.
According to the basic feature of the present invention the main
tubing is provided with a capillary slot, connected over the branch
line to takeoff means for the main fluid, the length of the
capillary slot in axial direction of the main tubing exceeding the
maximum contact length of a segmentation element in this
direction.
Inventors: |
Hrdina; Jiri (Praha,
CS) |
Assignee: |
Ceskoslovenska akademie (Praha,
CS)
|
Family
ID: |
5413088 |
Appl.
No.: |
04/857,956 |
Filed: |
September 15, 1969 |
Foreign Application Priority Data
|
|
|
|
|
Sep 19, 1968 [CS] |
|
|
6571/68 |
|
Current U.S.
Class: |
210/635;
210/198.2; 422/82; 436/53; 95/259 |
Current CPC
Class: |
G01N
35/08 (20130101); Y10T 436/118339 (20150115) |
Current International
Class: |
G01N
35/08 (20060101); B01d 019/00 () |
Field of
Search: |
;55/67,197,386,36,55
;73/23.1 ;210/31,198,65 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hart; Charles N.
Claims
I claim:
1. A method for withdrawing liquid samples from a stream flowing
through tubing, said stream being divided into segments by fluid
segmentation elements spaced apart from each other in the direction
of flow of said stream, said method comprising:
conducting said stream across a discharge port in said tubing;
causing said fluid elements to contact the discharge port along a
length of said port, said port having a length greater than the
length of said elements;
causing said fluid elements to remain within said tubing by having
the width of said discharge port less than the width of said
elements;
said elements having a diameter as large as the internal diameter
of said tubing and having an exterior film of sufficient tension to
retain said fluid therein while passing across said port;
withdrawing a portion of said liquid within said port by applying a
flow inducing pressure to said port without removing fluid from
said elements; and
conducting the remaining portion of said stream with said
segmentation elements therein in said flow direction downstream
from said port.
2. The method according to claim 1 including subjecting said liquid
to capillary action at said port, said segmentation elements having
different fluid properties and being unaffected by said capillary
action.
3. The method according to claim 1 including conducting liquid from
said port to a chromatographic flow cell, whereby successive liquid
segments of said stream pass continuously through said flow cell
for analysis.
4. In apparatus for liquid chromatographic apparatus of the type
including a chromatographic column, a tube for conducting a stream
of eluate liquid from the column for analyzing the eluate liquid,
and including a device for inserting fluid segmentation elements in
said tube at intervals in said eluate stream to divide said stream
into segments, said apparatus further including means for
separating said eluate liquid from said elements and the remainder
of said stream, said separating means comprising:
means forming a tubular passage for conducting the segmented fluid
stream from an upstream region to a downstream region, said passage
means having an impervious internal wall extending between said
regions and defining a flow passage for said stream,
said wall having a port in communication with said tubular passage,
said port having a length extending in the direction of flow
through said passage, whereby said length of said port is greater
than the length of said element, and having a width extending
transverse to the direction of flow in said passage, whereby said
port width is less than the width of said element said port length
being greater than said port width, and a discharge conduit
connected with said port for conducting eluate to said flow cell,
whereby the length of the elements introduced into said eluate
stream are shorter than the length of said port to allow eluate to
be drawn into said discharge conduit while surface tension in said
elements prevents entry of said element fluid into said discharge
conduit and said elements move continuously from said upstream
region to said downstream region while eluate liquid is withdrawn
through said discharge conduit.
5. The apparatus according to claim 4 wherein the width of said
port is of capillary size and is in the form of a continuous
slot.
6. The apparatus according to claim 4 including chamber means
between said port and said conduit for collecting said fluid.
7. The apparatus according to claim 5 including a plurality of
bridge members extending transversely across said port, said bridge
members being spaced apart from each other along the length of said
port.
8. The apparatus according to claim 5 including chamber means
between said port and said discharge conduit for collecting eluate
fluid.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings represent by way of example several
embodiments of the apparatus according to the invention.
FIG. 1 is a more or less diagrammatic view of a known laboratory
equipment in which the new method and apparatus for the separation
of segmentation elements is used,
FIG. 2 shows a diagrammatic longitudinal section through a simple
embodiment of the new apparatus, illustrating the principle of its
operation,
FIG. 3 is the corresponding cross-sectional view taken along the
line A--A of FIG. 2,
FIG. 4 is a longitudinal section through a modified embodiment of
the new apparatus, in a diagrammatic representation,
FIG. 5 is a longitudinal section through the new apparatus combined
into one unit with the flow cell of a measuring instrument, the
section being taken along the line B--B of FIG. 6,
FIG. 6 is a cross-sectional view of the apparatus shown in FIG. 5
and taken along the line C--C of FIG. 5,
FIG. 7 shows a longitudinal sectional view of the new apparatus of
a simple design, enabling an easy manufacture thereof,
FIG. 8 is the corresponding cross-sectional view, taken along the
line D--D of FIG. 7.
FIG. 9 shows another embodiment of the apparatus in a longitudinal
section,
FIG. 10 is the corresponding cross-sectional view taken along the
line E--E from FIG. 9,
FIG. 11 illustrates a further modification of the apparatus,
FIG. 12 is the corresponding cross-sectional view,
FIG. 13 shows the new apparatus combined with a flow cell in a
longitudinal section therethrough,
FIG. 14 a modified embodiment of the apparatus as combined with a
flow cell, in a longitudinal sectional view.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings in detail, FIG. 1 represents
diagrammatically an example of a laboratory appliance employing the
apparatus according to the invention. It has to be noted that this
appliance is not the subject of the present invention, it being
disclosed only for the purpose of assisting in a clear
understanding thereof. Further it has to be pointed out, that the
invention can be used in a great variety of combinations and in
connection with various appliances serving numerous purposes and
that the disclosure of this particular example of use should under
no circumstances be considered as limiting the scope of the
inventive idea.
FIG. 1 represents by way of example a chromatographic column 1,
which through a piping 2 supplies a pump 3 with a continuous stream
of eluate, carrying components, such as amino acids, separated by
the chromatographic action of the column. This stream will
hereinafter be termed "stream of the main fluid." The main fluid
(i.e., the eluate with components distributed therein in a definite
pattern), has to be measured, for instance by colorimetric means.
If no provision were made, it would happen that along the
relatively long path which the main fluid has to traverse, before
reaching the colorimeter, the individual separated components would
to a certain extent intermingle again, so that the result of the
separation of the components achieved by the chromatographic
process and therefore also the result of the analysis would be
greatly distorted.
This is why the stream of the main fluid is segmented, which means
that so-called "segmentation elements" are introduced into it
(preferably at predetermined spacings), said segmentation elements
consisting of bubbles of gas or drops of liquid, which are
substantially immiscible with the main fluid. The stream of the
main fluid is thereby divided into individual segments, which can
then traverse even a fairly long pipeline, without the contents of
the individual segments becoming intermingled to an undesirable
degree. This ensures that the measuring instrument is supplied with
the main fluid, in which the various components are distributed
substantially in the same pattern in which they left the
chromatographic column. In other words, the degradation of
concentration gradients, which would be unavoidable, if the stream
of main fluid were not segmented, is thereby to a high degree
eliminated.
The segmentation elements are introduced into the stream of main
fluid at required spacings by an apparatus, sometimes called
"bubbler" and marked in the example shown by the reference numeral
4, said bubbler being connected to a discharge pipe 5 of the pump
3. A gas (air, nitrogen or the like) is admitted into the bubbler 4
through a pipe 6 from a source 7, or, if air is used as the
segmentation medium, directly from the atmosphere. Alternatively
the bubbler 4' can be arranged immediately below the
chromatographic column and in this case the pipe 6' leads from the
pump 3 to the bubbler 4', as shown in dotted lines in FIG. 1. The
bubbler is a device well known in the art and will therefore not be
described in detail. Instead of a gas it is of course possible to
introduce into the stream of the main fluid a segmentation liquid,
such as mercury, oil or the like, in the form of drops, which are
likewise introduced into the main fluid stream by a known device
similar to the bubbler 4.
The segmented stream of the main fluid proceeds from the bubbler 4
through a pipe 8 to a heating bath 9, in which it is heated in a
coil 10 to the required temperature.
Before the stream of the main fluid is admitted to the measuring
instrument, it has to be freed from the segmentation elements
which-- as said above-- consist of a segmentation medium differing
from the main fluid to be measured. The presence of this
segmentation medium in the measuring instrument would interfere
with its operation and lead to incorrect results.
The segmentation elements are eliminated from the stream of main
fluid by a method forming the subject of the present invention and
for performing the method an apparatus is used, which forms
likewise a part of the present invention and is marked generally
with the reference numeral 11 in FIG. 1. The method as well as the
apparatus for the elimination of segmentation elements according to
the invention will be described in detail here below.
The segmented main fluid is admitted into the apparatus 11 through
a tubing 12. The apparatus 11 is provided on the one hand with a
tubing 13 leading to the drain or to a place of further treatment
and, on the other hand, with a tubing 14 (which hereinafter will be
called "branch line"), connected to a measuring instrument, in the
present example a colorimeter 15. The latter is connected to a
recorder 16, serving to record the results of the measurement. A
flow cell (not shown in FIG. 1) of the colorimeter 15 is attached
to a takeoff tube 17, which in the example shown leads to a suction
pump 18 forming preferably one unit with the pump 3. The discharge
side of the pump 18 is provided with a pipe 19 leading to the
waste.
In a preferred embodiment the pump 3 is of the so-called
peristaltic type. Such pump conveys a liquid, contained between
resilient walls of a rubber tube or diaphragm, by a successive
compression of said resilient walls by means of pressure members,
such as a system of rollers rolling forward along the outside of
the resilient wall, thereby forcing forward the medium enclosed
between the resilient walls. The operation of the peristaltic pump
3 and the bubbler 4 can be synchronized in any suitable way, to
make the bubbler 4 inject the segmentation elements in accordance
with the individual batches of liquid, supplied by the pump 3.
The operation of the device shown in FIG. 1 may be already clear
from the preceding description, but for the sake of completeness it
will be summed up as follows:
A continuous stream of the main fluid emerging from the
chromatographic column 1 is dosed by the pump 3 into the bubbler 4,
where it is segmented by the injection of gas bubbles (or drops of
liquid), forming segmentation elements. The segmented stream
proceeds through the heating bath 9 to the apparatus 11 serving for
the elimination of segmentation elements; a continuous stream of
the main fluid is taken off the apparatus 11 through the branch
line 14 and fed to the colorimeter 15, where it is measured and the
result recorded in the recorder 16. The segmentation medium,
together with the remainder of main fluid, proceeds to the tubing
13 either to further treatment or to the waste. The main fluid is
taken off by the pump 18 through the flow cell of the colorimeter
15 and, after the measurement has been effected, it advances
through the tube 17 and pump 18 to the waste pipe 19.
FIGS. 2 to 14 illustrate embodiments of the apparatus according to
the invention. As shown in FIG. 2, the apparatus 11 is supplied
with a stream of the main fluid 21, segmented by elements 22, which
advances through a main tubing 23 in the direction of the arrow M.
Provided in the main tubing 23 is a capillary slot 24, which is
connected either directly or via a relatively small collecting
space 25 to a branch line 26 (corresponding to the branch line 14
in FIG. 1), which is connected to a source of suction either
directly or through a measuring instrument, as shown in FIG. 1,
where the source of suction is represented by the suction pump
18.
The element 22 contacts the wall of the main tubing 23 in axial
direction along a length, marked L in FIG. 2. This length is called
"contact length" throughout this specification.
The length of the slot 24, in the flow direction of the segmented
stream, exceeds the maximum contact length of a segmentation
element in this direction. The width of the slot 24 has capillary
dimensions, which means that its dimensions are such as to produce
capillary effects between the segmentation medium (elements) and
the material of the main tubing 23, said effects being usually
described as capillary ascension and capillary depression.
The apparatus described operates as follows:
The segmented stream of the main fluid advances through the main
tubing 23 along the capillary slot 24. As long as the slot 24 is in
contact with the main fluid 21, the latter is sucked (or conveyed
by another action) through this slot into the collecting space 25
and further through the branch line 26 for further use. If a
segmentation element 22 comes into contact with the slot 24, it
does not pass through the slot 24, but proceeds further through the
main tubing 23 in the direction of the arrow M for the following
reasons:
A segmentation element 22 is actually a bubble of a gas or a drop
of a liquid enclosed in another medium, with which it does not mix;
the surface of the bubble or drop shows a surface tension on the
curved surface, the resulting force being directed towards the
interior of the bubble and tending to shape it into a ball of the
smallest volume. If no outer influences acted on the bubble, this
surface tension would prevent any deformation of the bubble, which
therefore would be unable to penetrate through the capillary slot
24, whose lateral (capillary) dimension is far smaller than the
diameter of the bubble.
The bubble could pass through the capillary slot 24 only then, if
the combined effect of all outer influences, to which the bubble is
subjected, would overcome the resistance resulting from its surface
tension and capillary forces acting against deformation to a
dimension equaling the width of the capillary slot. Only in this
case would the bubble be forced into and through the slot 24. The
bubble is subject particularly to the hydrodynamic pressure
occuring during the flow of the fluid, hydrostatic pressure of the
fluid, which causes the flow, further to the capillary effect of
the slot 24 and further to the take off (suction) effect in the
slot 24, produced by the takeoff branch line 26. A decisive part
plays further the surface affinity of the segmentation medium to
the material of the tubing 23 in which the slot 24 is provided.
According to the invention this combined effect of the outer
influences acting on the bubble is maintained at a value lower than
the resistance of the capillary forces and surface tension of the
bubble against deformation to a dimension equaling the width of the
capillary slot 24 (so-called "critical resistance against
deformation"). In this way the entry of bubbles (or drops) of the
segmentation medium through the slot 24 and thereby to the branch
line 26 is positively avoided, so that it is only the main fluid
that flows in a continuous stream through the branch line 26.
These outer influences are controlled by the regulation of
pressures under which the segmented stream is passed through the
main tubing 23, further by the take off forces in the branch line
26 and, in particular, by the dimension of the slot 24 in
transverse direction, which has a decisive influence on its
capillary effect. This dimension is chosen according to given
conditions and, as mentioned above, depends to a considerable
degree on the character of the materials used (segmentation medium
and material of the wall in which the slot 24 is arranged).
Under the effect of outer pressures to which the segmentation
element is subject, the boundary or outer surface of the
segmentation element penetrates slightly into the slot 24, in which
it assumes a considerable curvature (meniscus) in transverse
direction, as indicated by 27 in FIG. 3; however, the element does
not pass through the slot 24, but advances further through the main
tubing 23 in the direction of the arrow M.
In order to take off the main fluid from one single or not more
than two adjacent segments of the main fluid, the length of the
slot 24 is chosen such, as to exceed the maximum contact length of
a segmentation element, but shorter than, or equal to, the distance
between the removed surfaces of two neighboring elements.
The main fluid will be taken off through the slot 24 under all
circumstances without running the risk, that the segmentation
element could interrupt the flow of main fluid into the slot. From
FIG. 2 it is also evident that the main fluid will flow into the
slot 24 either from a single or from not more than two adjacent
segments, with the result that contamination by the contents of a
greater number of segments is practically eliminated but not from
an indefinite number of segments-- which danger occurs in the known
debubblers.
In some cases, where accuracy is not the primary consideration, and
where emphasis is placed on a certain degree of smoothing or
levelling the differences in quality of the individual segments or
on a high flow rate of the main fluid, the slot 24 may be extended
over a number of segments of the main fluid, so that the latter is
taken off from a greater number of segments simultaneously. This
results, of course, in a levelling effect on the concentration
gradients etc., and smoothing in a certain degree the resulting
record line.
The area of the slot 24 or the collecting space 25 is so small,
that the stagnation of the liquid occuring therein and therefore
the undesirable mixing, are completely negligible and practically
do not influence the accuracy of measuring at all.
In a practical embodiment the diameter of the main tubing may be
e.g., 1 mm. or less and the transverse dimension of the capillary
slot 0,3 to 0,5 mm. If the diameter of the main tubing is larger,
the transverse dimension of the slot 24 may be larger as well, such
as 1 mm., which is sometimes preferable for technological
reasons.
FIG. 4 represents a modified embodiment of the new apparatus. The
capillary slot in this case consists of a plurality of partial
channels 28, opening into a main tubing 29 through capillary
openings 30. The channels 28 communicate with a collecting conduit
or space 31, attached through a branch pipe 32 to a source of
suction. The total length of the system of partial channels 28 in
the direction of the axis of the main tubing 29 is larger than the
maximum contact length of a segmentation element 33 and preferably
smaller than, or equal to, the distance between the remote surfaces
of two neighboring elements. If necessary, however, this dimension
can be even larger for reasons indicated in connection with the
embodiments shown in FIGS. 2 and 3.
Under the influence of outer pressures, the outer surface of the
segmentation elements 33 is pressed slightly into the openings 30
of channels 28, where it becomes considerably curved, both in a
plane perpendicular to the axis of the main tubing as well as in a
plane containing this axis, but it does not penetrate through the
partial channels and advances further through the main tubing in
the direction of the arrow N.
In the embodiments according to FIGS. 2 and 3, as well as FIG. 4 a
considerable portion of the main fluid may be taken off from the
main tubing 23 or 29 during the passage of the various segments
over the slot 24 or channels 28, so that in the main tubing 23 or
29 there may remain a small residuum of the main medium, for
instance not more than 10 percent, between the various elements of
the segmentation medium (which of course has not been withdrawn
into the branch line).
The main fluid can be fed into the branch line 26 or 32 either by
the effect of suction produced by a suction pump (as indicated in
FIG. 1), or in any other suitable way.
FIGS. 5 and 6 show a practical embodiment of the new apparatus in
combination with a flow cell. In a block 34, with an attachment 35,
made e.g., of transparent organic glass or any other suitable
material, the main tubing is produced by a boring 36 (see
particularly FIG. 6). Attached to the boring 36 at one side is a
supply tubing 37 and at the other side a discharge tubing 38. A
capillary slot 39 is provided in the block 34 and, as near as
possible to the slot 39 a flow cell 40 is arranged and covered from
both sides with covers 41, 41' made of a transparent material. The
capillary slot 39 communicates with the flow cell 40 over a channel
42, which is relatively short and opens to one side of the flow
cell 40. The other side of the flow cell 40 communicates with a
hollow needle 43, attached to the branch line for the takeoff.
The capillary slot 39 is rounded or tapered at its ends, in order
to eliminate sharp corners, however slight, which might adversely
affect and perhaps interfere with the operation of the
apparatus.
The embodiment shown in FIGS. 5 and 6 has the advantage that the
stream of main fluid enters the flow cell 40 along a very short and
narrow path, with the result that a possible degradation of the
concentration gradients is restricted to a minimum (it has to be
noted that in the slot 39 and channel 42 the main fluid is not
segmented any more). The block 34 with the flow cell 40 is inserted
in a measuring instrument of a known type, of which only the
diaphragm 44,45 are shown for the sake of completeness.
FIGS. 7 and 8 show another simple embodiment of the new apparatus.
The main tubing consists of a tube 46, in which a capillary slot 47
is cut. The tube 46 is inserted in the boring of a bushing 48.
Coaxially attached to the tube 46 is a supply tube 49 and a
discharge tube 50. Opposite the slot 47 and in open communication
therewith is a hollow needle 51 arranged in the bushing 48 and
connected to a takeoff device. The slot 47 is tapered at both ends
of the tube 46 by inlays 52 of any suitable material, secured in
these places and serving to eliminate any sharp corners.
FIGS. 9 and 10 show another modification of the new apparatus. Cut
in a tube 53 is a circular groove 54 extending diametrically
through the tube, as shown in FIG. 9, so that at the point 55 there
is produced a capillary slot of the desired shape, whose ends are
already rounded. The portion 56 of the slot in the opposite wall of
the tube 53 is closed by means of a seal 57, blending with the wall
of the tube 53, which is inserted into the boring of a bushing 58.
A hollow needle 59, attached to a takeoff device, is inserted in
the bushing 58 opposite the slot 55 and in open communication
therewith.
FIGS. 11 and 12 are illustrations of another simple arrangement. A
slot 60 is cut in a tube 61 from one side only and inlays 62, 62'
are fitted at both ends thereof, to impart the desired tapered or
rounded shape to the slot 60, as indicated in FIG. 7. The tube 61
is then inserted into a boring in a block 63 housing a hollow
needle 64, which communicates with the slot 60.
FIGS. 13 and 14 represent a combination of an apparatus, designed
as above, with a flow cell into one unit, similar to the
arrangement shown in FIGS. 5 and 6, the only difference being, that
according to FIG. 13 a block 65 housing a flow cell 66 carries a
block 67 corresponding substantially to the block 63 according to
FIGS. 11 and 12, a tube 68 and a slot 69 being provided in the
block 67. According to FIG. 14 the block 70, housing a flow cell
71, carries a cylindrical bushing corresponding substantially to
the bushing 48 shown in FIGS. 7 and 8 or to the bushing 58 shown in
FIGS. 9 and 10.
In an alternative embodiment of the invention it is possible to
change the characteristics of the process in such a way that the
tapped stream has not the form of a continuous stream (of main
fluid) but likewise of a segmented stream. The conditions, i.e.,
pressures etc., are chosen such that in addition to the main fluid
a part of the segmentation medium penetrates through the capillary
slot, with the result, that in the branch line a segmented stream
is obtained as well. This may be advantageous in some special
cases.
* * * * *