U.S. patent number 3,647,070 [Application Number 05/047,495] was granted by the patent office on 1972-03-07 for method and apparatus for the provision of fluid interface barriers.
This patent grant is currently assigned to Technicon Corporation. Invention is credited to Stanford L. Adler.
United States Patent |
3,647,070 |
Adler |
March 7, 1972 |
METHOD AND APPARATUS FOR THE PROVISION OF FLUID INTERFACE
BARRIERS
Abstract
New and improved method and apparatus for the provision of a
satisfactory physical and chemical barrier at a fluid interface in
the nature of that which occurs at the interface of the separated
plasma and packed cells layers in centrifuged blood samples are
provided, and are embodied by barrier means which are of greater
specific gravity than said blood plasma layer but lesser specific
gravity than said blood cells layer and are operable, upon
insertion into a centrifuged blood sample container, to sink
through said blood plasma layer substantially to said interface and
to be wetted and expanded by said blood plasma to expand into firm
contact with each other and with the walls of said container to
automatically form said barrier at said interface.
Inventors: |
Adler; Stanford L. (Monsey,
NY) |
Assignee: |
Technicon Corporation
(Tarrytown, NY)
|
Family
ID: |
21949300 |
Appl.
No.: |
05/047,495 |
Filed: |
June 11, 1970 |
Current U.S.
Class: |
210/789; 210/361;
210/518; 210/516 |
Current CPC
Class: |
G01N
33/491 (20130101) |
Current International
Class: |
G01N
33/49 (20060101); B01d 021/26 () |
Field of
Search: |
;210/78,83,361,362 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Adee; John
Claims
What is claimed is:
1. In a method of effecting the substantial physical and chemical
separation of the respective blood plasma and blood cell layers of
a blood sample, which resulted from the centrifugation thereof, by
the formation of a physical and chemical barrier in the blood
sample container substantially at the interface of said blood
plasma and blood cell layer, comprising the steps of, inserting
barrier means into said blood sample container and through said
blood plasma layer, so as to be located substantially at said
interface, structuring said barrier means to pass freely through
said blood plasma layer and to be ineffective to form said barrier
when initially positioned at said interface, and forming said
barrier means of a material having a greater specific gravity than
said blood plasma layer but a lesser specific gravity than said
blood cell layer, so as to sink through said blood plasma layer to
said interface, said material forming said barrier means
characterized as being expandable when wetted, so as to expand into
firm contact with the walls of said container to define said
barrier at said interface.
2. The method of claim 1, further comprising the steps of, forming
said barrier means of granules of said expandable material, which
upon being wetted expand into firm contact with each other and said
walls of said container to define said barrier at said
interface.
3. In an apparatus for effecting the substantial physical and
chemical separation of the respective blood plasma and blood cell
layers of a blood sample, which result from the centrifugation
thereof, by the formation of a physical and chemical barrier in the
blood sample container substantially at the interface of said blood
plasma and blood cell layers, comprising barrier means for
insertion into said blood sample container, said barrier means
being structured to pass freely through said blood plasma layer, so
as to be located substantially at said interface and to be
ineffective to define a barrier when initially located at said
interface, said barrier means comprising a material having a
greater specific gravity than said blood plasma layer and a lesser
specific gravity than said blood cell layer, so as to sink through
said blood plasma layer to said interface, said material
characterized as being expandable when wetted, so as to expand into
firm contact with the walls of said container to define said
barrier at said interface.
4. In apparatus as in claim 3 wherein, said barrier means comprises
granules of said expandable material, said granules, when wetted,
expanding into firm contact with each other and with the walls of
said container to define said barrier at said interface.
5. In apparatus as in claim 3 wherein said barrier means is formed
of a single body of said material, said body, when wetted,
expanding into firm contact the walls of said container to define
said barrier at said interface.
6. In an apparatus as in claim 3 wherein, said material is an
nonionic, hydrophylic polymeric material selected from the group
consisting of polyhydroxyethylmethacrylate and polyacrylamide
hydrogel.
7. In apparatus as in claim 3, wherein said material is an
insoluble cellulose spongelike material having one or more coatings
of a nonionic, hydrophylic polymeric material applied thereto to
delay the wetting and separation thereof until said body is located
substantially at said interface.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to new and improved method and apparatus for
the provision of a satisfactory physical and chemical barrier at a
fluid interface in the nature of that which occurs at the interface
of the separated plasma or serum and packed cells layers in
centrifuged blood samples.
2. Description of the Prior Art
In the automatic analysis of blood samples through the use of
improved versions of automated analysis apparatus in the nature of
those described in U.S. Pat. No. 3,241,432, issued Mar. 22, 1966,
to Dr. Leonard P. Skeggs, et al. and assigned to the assignee
hereof, and marketed for example as the "SMA 12/60 Auto-Analyzer"
by said assignee, it may be understood that a not insubstantial
period of time may elapse between the removal of the blood sample
to be analyzed from the patient in question and the automated
processing and analysis of said blood sample by said analysis
apparatus. As a result, it may be understood to be standard
laboratory procedure, following the suitable centrifugation of each
of said blood samples to separate the blood sample plasma or serum
and blood sample cells into contiguous layers (it being the plasma
or serum which is to be analyzed), to manually decant or otherwise
remove the plasma or serum from the packed cells portion of a
centrifuged blood sample prior to the analysis thereof to prevent
unwanted changes in some of the blood sample constituents of said
plasma or serum for which said automated analysis is to be
effected. More specifically, it may be understood that such
constituents may, for example, include serum potassium, glucose,
and certain blood enzymes, and that said unwanted changes therein
would occur as a result of ionic or other contaminant diffusion
from said cells to said plasma or serum layer at the interface
thereof.
The significant disadvantages of this manual plasma/cells
separation technique insofar as the tediousness and time consuming
nature thereof are believed readily apparent. Of even more
significant disadvantage, however, is the fact that the same gives
rise to the basically unacceptable risk of the loss of blood sample
identification that can occur as a result of the transfer of a
portion (here the separated plasma or serum) of a blood sample from
the original container bearing the blood sample identification
information to another container, and the necessity for accurate
transcription of the blood sample identification information along
to said other container. Thus, and although barrier devices are
known in the prior art which may be inserted or added to the
container of a blood sample which has been separated by
centrifugation into a plasma or serum layer and a packed cells
layer, it may be understood that such devices will not, in general,
be found to provide both the requisite satisfactory physical and
chemical separation that is required in order to enable the
respective plasma and packed cells layers to remain in the same
container, to render loss of identification of the former
impossible, while substantially preventing adverse effects upon the
subsequent automated quantitative analysis of said separated
plasma.
OBJECTS OF THE INVENTION
It is, accordingly, an object of this invention to provide new and
improved method and apparatus for the satisfactory physical and
chemical separation between separated fluid layers of differing
densities within the same container.
Another object of this invention is the provision of apparatus as
above which are automatically and accurately operable upon the
insertion thereof into said separated fluid layers within said
container.
Another object of this invention is the provision of apparatus as
above which are of particularly low cost.
Another object of this invention is the provision of method and
apparatus as above which are particularly adapted for use in
conjunction with automated fluid processing and testing
equipment.
A further object of this invention is the provision of method and
apparatus as above which are particularly adapted for use in
providing for the satisfactory physical and chemical separation in
the same container between the respective plasma or serum and
packed cells layers of centrifuged blood samples.
SUMMARY OF THE DISCLOSURE
As disclosed herein, the new and improved method and apparatus of
the invention comprise the addition of barrier means to the
tubelike container of a centrifuged blood sample which has been
separated into a plasma or serum layer and a more dense packed
cells layer. Said barrier means may, for example take granular,
ellipsoidal, disclike or spherical form, and may be made from a
readily wettable and expandable material in the nature of a
nonionic hydrophilic polymer, or a synthetic sponge. The specific
gravity of said barrier means is predetermined to be greater than
that of said plasma and less than that of said packed cells. Upon
addition to the centrifuged blood sample, said barrier means will
sink through said plasma layer for suspension in the same at the
plasma/packed cells interface, will be wetted by said plasma and
expanded for adhesive and cohesive formation of a barrier at said
interface in said container to physically and chemically separate
said plasma and packed cells layers and prevent cellular diffusion
from the latter to the former. In other disclosed forms, said
barrier means comprise sleeve and stopper means which are
operatively associated with said centrifuged blood container and
are automatically operable upon appropriate insertion thereinto to
form the desired physical and chemical barrier between said plasma
and packed cells layers.
DESCRIPTION OF THE DRAWINGS
The above and other objects and significant advantages of this
invention are believed made clear by the following detailed
description thereof taken in conjunction with the accompanying
drawings wherein:
FIG. 1 is a perspective view of a first form of barrier means
constructed in accordance with the teachings of this invention;
FIGS. 2 and 3 illustrate the application of the barrier means of
FIG. 1 to a centrifuged blood sample;
FIG. 4 is a perspective view of a second form of barrier means
constructed in accordance with the teachings of this invention;
FIGS. 5 and 6 illustrate the application of the barrier means of
FIG. 4 to a centrifuged blood sample;
FIG. 7 is a perspective view of another form of barrier device
constructed in accordance with the teachings of this invention;
FIG. 8 is a perspective view of still another form of barrier means
constructed in accordance with the teachings of this invention;
FIG. 9 is a cross-sectional view of automatic, barrier means
dispensing means;
FIG. 10 illustrates the barrier means dispensing means of FIG. 9 in
operative relationship with blood sample processing equipment;
FIGS. 11 through 14 illustrate another form of the barrier means of
the invention; and
FIG. 15 illustrates a modification of the form of the barrier means
of the invention of FIGS. 11 through 14.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIG. 1, a form of the new and improved
plasma/cells barrier means of the invention is indicated generally
at 10 and comprises a plurality of granules 12 of a suitable
material in the nature of a nonionic, hydrophylic polymer, or other
material, that would function in a similar manner in the presence
of a plasma liquid. More specifically, the granules 12 may, for
example, be formed from the nonionic, hydrophylic polymers
identified as polyhydroxyethylmethacrylate, or polyacrylamide
hydrogel, and, as such, would of course have a substantial affinity
for water and would be expandable in all directions upon the
wetting thereof by a plasma or serum liquid.
For use in accordance with the teachings of this invention in
providing for a satisfactory barrier between the separated plasma
or serum and packed cells portions of a blood sample as illustrated
in FIGS. 2 and 3, it may be understood that the specific gravity of
the granules 12 is controlled in the formation thereof to insure
that the same will be denser than blood plasma or serum, but less
dense than the packed blood cells so that said granules will float
substantially at the interface of separated plasma and cells.
More specifically, and as best seen in FIG. 2 wherein a suitable
blood sample container or tube which may, for example, take the
form of a Vacutainer, is indicated at 14 and includes therein a
blood sample which has been separated by appropriate centrifugation
into a packed cell layer 18 and a plasma or serum layer 16 having
an interface 20, the introduction as illustrated of a plurality of
the granules 12 into the centrifuged blood sample container 14 will
result in the said granules sinking through the less dense plasma
layer 16 to float at or assume the depicted position thereof in
said plasma layer substantially at the interface 20 of the same and
the more dense packed cells layer 18. As this occurs, it may be
understood that the wetting of the granules 12 by the plasma liquid
will, of course, soon commence the expansion of the former
substantially in all directions with the result that the said
granules will expand into firm cohesive and adhesive contact with
each other and with the inner wall surface of the tube 14 to
ultimately form a substantially integral plug 22 as depicted in
FIG. 3 at the plasma/cells interface 20. The length of time
required for the information of plug 22 will be dependent, in part,
upon the compacting pressure utilized in the formation of the
granules 12 and may, for example, be arranged to occur within three
to ten minutes as desired.
The extent of this expansion of the granules 12 will be sufficient
to actually give rise to an outwardly directed physical pressure on
said inner wall surface of the tube 14, whereby may be understood
that the thusly formed plug or barrier 22 will provide a firm and
not readily displaceable physical barrier between the plasma layer
16 and packed cells 18, which barrier will be capable of
withstanding substantial vibration without fracture, and will be of
sufficient strength to enable the turning over of the tube 14
without packed cells spillage or runoff into said plasma layer.
In addition to providing for an excellent physical barrier between
the plasma layer 16 and the packed cells layer 18, it may be
understood that the plug 22 will be effective to prevent ionic
and/or other cellular contaminant diffusion between the packed
cells layer 18 and the plasma or serum layer 16 to thus prevent
changes that might otherwise occur in some of the blood
constituents, such as serum potassium, glucose and certain enzymes,
for which subsequent quantitative analyses may be performed on said
plasma or serum layer. Accordingly is believed made clear that the
actual physical and chemical separation provided by the plug 22
between the plasma or serum layer 16 and the packed cells layer 18
will, under normal use and environmental conditions, be the
substantial equivalent of that which would be provided by
independent tubes or containers therefor.
Referring now to the form of the plasma/cell barrier means of the
invention as depicted in FIG. 4, the same may be seen to take the
shape of a disc 24 which may, for example, be made from the same
nonionic, hydrophilic polymeric materials referred to hereinabove
with regard to the granules 12 of FIG. 1. The specific gravity of
the disc 24 is again controlled in the formation thereof as through
variation in the amount of compacting pressure utilized in disc
formation to provide a disc which is more dense than the plasma or
serum and less dense than the packed cells. In this regard, it may
be understood that something in the range, for example, of 500 to
10,000 p.s.i. compacting pressure has proven particularly suitable
in providing a disc 24 of lesser density than the packed cells
layer 18 but of greater density than the plasma or serum layer
16.
For use in accordance with the teachings of this invention in
providing for a satisfactory chemical and physical barrier between
the respective separated plasma or serum and packed cells layers 16
and 18 of a Vacutainer or like tube 14 containing an appropriately
centrifuged blood sample as depicted in FIGS. 5 and 6, it may be
understood that the disc 24 would initially be dimensioned so that
the same would fit with suitable clearance as indicated at 26
within the tube 14, whereby is believed made clear that insertion
of said disc thereinto will, of course, result in said disc sinking
through the plasma layer 16 and coming to rest substantially in the
latter at the plasma/cells interface 20 substantially as depicted
in FIG. 5.
Following this, it may be understood that the wetting of the disc
24 by the plasma liquid will result in the expansion of the disc
polymer as described into firm cohesion, and into firm adhesive
contact with the inner wall surface of the tube 14, to the relative
size and position of the disc 24 as depicted in FIG. 6 to form the
desired physical and chemical plasma/cells barrier. Again, as
discussed hereinabove with regard to the granules 12, it may be
understood that the plug or barrier formed by the expanded disc 24
will actually exert physical pressure against the inner wall
surface of the blood sample container 14 and will be effective to
maintain the desired plasma/cells separation despite reasonable
container vibration and/or turning over of the latter.
Another form of the plasma/cells barrier means of the invention is
illustrated in FIG. 7 and may be seen to take the form of an
elipsodial member 28 which may again, for example, be made from the
nonionic, hydrophilic polymeric materials discussed hereinabove and
will, of course, function in the nature of the disc 24 of FIG. 4 to
provide the desired physical and chemical barrier between the
plasma or serum layer 16 and the packed cells layer 18. More
specifically, it is believed clear that the elipsoid 28 would be so
dimensioned that the diameter D (FIG. 7) thereof would be somewhat
less than the internal diameter of the blood sample container or
tube 14 whereby the elipsoid 28 may be oriented as depicted in FIG.
7 and inserted with clearance into the tube 14, in the manner of
the disc 24 as depicted in FIG. 5, sink through the plasma layer 16
substantially to the plasma/cell interface 20, and expand through
the wetting thereof by the plasma liquid into firm surface contact
with the inner wall surface of the tube 14 to form the desired
physical and chemical plasma/cells barrier.
Another form of the plasma/cell barrier means of the invention is
indicated at 30 in FIG. 8 and, as depicted therein, may be seen to
again take the shape of a disc which, in this instance, is
preferably made from a compressed synthetic sponge material in the
nature of an insoluble cellulose sponge material which is compacted
under suitable pressure to provide for the desired density thereof
relative to the respective plasma or serum and cells layers as
discussed hereinabove, and which may, in addition, be coated with
one or more layers of a solution of the nonionic, hydrophilic
polymeric materials referred to hereinabove to delay the wetting
thereof by the plasma liquid. More specifically, it may be
understood that the use of a number of coatings of such polymeric
materials of the disc 30 as may be applied, for example, by the
dipping of the said disc in a solution of said polymeric materials,
will function to provide for a time delay to delay the wetting and
attendant expansion of the synthetic sponge material until the disc
30 has assumed the proper level in the blood sample container 14
just above the plasma/cells interface 20 in the manner clearly
illustrated for the disc 24 in FIGS. 5 and 6. The function of the
synthetic sponge material disc 30 is, of course, quite analogous to
that of the nonionic, hydrophillic polymeric material disc 24 of
FIG. 2 in that the wetting of the former by the plasma liquid will,
of course, effect the expansion thereof against the inner wall
surfaces of the tube 14 to thus provide the desired physical and
chemical plasma/cells separation.
Automatic dispensing apparatus for the automatic dispensing of
discs in the nature of 24 or 30 into Vacutainers or other
containers 14 which contain centrifuged blood samples including a
plasma or serum layer 16 and a packed cells layer 18, are indicated
generally at 31 in FIG. 9 and, as depicted therein, may be seen to
comprise a generally elongated, cylindrical container 32 having a
base plate 34 and within which are stacked as shown a plurality of
said discs as here indicated at 36. A disc dispensing slot is
indicated at 37 and is formed as shown at the lower extremity of
the disc container 32.
A leafspring is indicated at 38 and is affixed as indicated to the
disc container 32 by attachment means 40. A slot 42 is provided in
the container 32 adjacent the lower extremity thereof and the
adjacent end 44 of the leafspring 38 is extendable therethrough as
shown. A cam is indicated at 46 and is drivingly rotatable about an
axis 48. The cam 46 and leafspring 38 are cooperatively associated
as depicted in such manner that each rotation of the former will be
effective to move the latter from the position thereof depicted in
solid lines to the position thereof depicted in dashed lines within
the container and enable the return thereof to the former position.
A cap 50 is provided for the container 32, and a coilspring 52 is
operatively associated therewith and with plunger means 54 to
maintain a substantial downward pressure of the stack of discs
36.
With the respective components of the plasma/cells barrier means
dispenser 31 arranged and operative as described, and a container
14 of a centrifuged blood sample arranged relative thereto as
shown, it is believed clear that each complete, driven rotation of
the cam 46 will be effective to dispense one of the discs 36 from
the container 42, under the action of the end 44 of leafspring 38
thereon, into the adjacent container 14 of a centrifuged blood
sample in the manner and along the general trajectory as indicated
by the just-dispensed barrier disc 36a and the dashed lines drawn
therewith. For purposes of preventing entrapment of air by the said
disc as the same enters the plasma layer 16 in the tube 14, it may
be understood that the disc dispenser 31 and tube 14 are preferably
arranged in such manner that the disc 36a will enter the said
plasma layer substantially edge-first to thus substantially prevent
or inhibit such entrapment of air.
Following such dispensing of the disc 36a in the manner described,
it is believed clear that the same will, of course, sink through
the plasma layer 16 to the desired position thereof just at the
plasma/packed cells interface 20 and, after the expiration of the
predetermined period of wetting time, will expand into firm contact
with the inner surface wall of the tube 14 to thus provide the
desired physical and chemical barrier as described in detail
hereinabove.
An application of the automatic disc dispenser 31 to the insertion
of a barrier disc in each of a plurality of tubes 14 as are
supported in a generally circular array thereof on the blood sample
tray of a sample tray centrifuge is depicted in FIG. 10, and as
seen therein, comprises said sample tray as indicated at 56 which
is rotatable at high speed from drive motor 58 through drive shaft
60. For centrifugation of the respective blood samples which are
contained in the tubes 14, it may be understood that the sample
tray 56 would be rotated by drive motor 58 at high speed while the
respective blood sample containers 14 would be allowed to pivot
radially outwardly from the respective upper portions thereof as
well known to those skilled in this art to effect the centrifuging
of the respective blood samples contained therein.
Following this, and after the sample tray 56 has come to a halt,
the disc dispenser means 31 would be operatively positioned
relative thereto as shown and operated, through rotation of cam 46
in synchronism with the indexing of the sample tray 56 through each
individual blood sample tube position thereof, to automatically
dispense a barrier disc as again illustrated by disc 36a into each
of said blood sample tubes to effect the provision of a
satisfactory physical and chemical barrier between the respective,
separated plasma or serum and packed cells layers as are now
contained in each of said tubes. Subsequently, the sample tray 56
may, if desired, be readily and conveniently operatively positioned
on automated blood sample supply, treatment and analysis means of
the nature disclosed, for example, in said U.S. Pat. No. 3,241,432,
for the subsequent, automated quantitative analysis of the
separated plasma or serum portion of each of said blood samples
with regard to a plurality of constituents thereof.
Of particularly significant advantage here, however, is the fact
that the new and improved plasma/cells barrier means of the
invention provides a satisfactory physical and chemical barrier
between the respective separated plasma and packed cells layers of
each of said blood samples to thus prevent changes in the former as
might otherwise occur to inhibit the accurate quantitative analysis
thereof while, at the same time, rendering substantially impossible
any loss of identification of a said blood sample by insuring that
the respective separated plasma and packed cells layers thereof are
maintained in the same tube. Thus, loss or mixup in blood sample
identification insofar as confusion of the separated plasma and
packed cells from the same blood sample is concerned, are rendered
substantially impossible.
A further form of the new and improved plasma/cells barrier means
of the invention is indicated generally at 62 in FIGS. 11 through
14 and, as best seen in FIGS. 11 and 12, comprises a container
assembly 63 including a Vacutainer or like tube 64 having a sleeve
66 insertable thereinto as shown in generally fluidtight manner as
provided by annual stop 68 and generally wedge-shaped soft plastic
sealing ring 70.
The sleeve 66 terminates as shown in a generally truncated
cone-shaped end portion 72 having an opening 74 formed centrally
thereof and screw threads 76 formed on the exterior surface
thereof. A sample sleeve cap 78 (FIG. 11) is provided, as is a
sleeve cap 80 (FIG. 12) which includes a glass or plastic rod 82
extending therefrom as shown and terminating in a plug or stopper
84 which is effective to substantially plug the opening 72 as
illustrated in FIG. 42. An end portion cap 86, which is screw
threaded as indicated at 88, is also provided and is effective to
screw over the sleeve end portion 72 to seal the same as
illustrated in FIG. 13.
In use, the container assembly 63 which may, for example, contain a
suitable anticoagulant, is filled with a whole blood sample and
mixed, following which the cap 78 is removed. The said container
assembly is then centrifuged to result in the separation of said
blood sample into a plasma or serum layer 90 and a packed cells
layer 92 having an interface 94, and it may be understood that the
distance between the upper end of sleeve opening 74 and the bottom
of container 64 is predetermined, in accordance with the largest
anticipated volume of the packed cells after configuration, to
insure that said interface 94 falls as shown below the upper end of
the opening 74. Knowledge that the volume of packed cells will
rarely, if ever, exceed 60 percent of the total blood sample volume
will, of course, be a principal factor in such distance
determination.
Following this blood sample centrifugation, cap 80 containing rod
82 and stopper 84 is inserted as shown into sleeve 66 with
resultant substantial sealing of the opening 74 by stopper 84 and
attendant containment of plasma or serum, only, from plasma or
serum layer 90 in the now completed sleeve assembly. Subsequently,
said plasma-containing completed sleeve assembly is removed from
the tube 64 in obvious manner and the threaded cover 86 is attached
as illustrated in FIG. 13 to the sleeve end portion 72 to insure a
leakproof blood plasma or serum container for plasma shipment if
desired. Removal of the cap 80 from the covered sleeve 66 will, at
this point, of course render the latter suitable for direct use as
the blood plasma container on the sample tray of automated blood
analysis apparatus as discussed above. If desired, the now distinct
packed cells layer 92 remaining as shown in FIG. 14 may be stored
through the simple utilization of the cap 17 as illustrated in said
FIG.
Of particular significance with regard to the sleeve 66 and tube 64
is the face that the same originate as the same container assembly
63 and would be so marked by appropriate blood sample
identification information formed on each prior to separation
thereof, whereby loss of identification, for example, of the
separated plasma or serum layer removed therefrom as described is,
of course, rendered impossible.
Referring now to FIG. 15, it may be seen that cap 80 including rod
82 and stopper 84 may be eliminated and far simpler sleeve-opening
closure means substituted therefor. More specifically, such
sleeve-opening closure means may be seen to take the form of a
simple metal or plastic ball 94 of suitable density which, when
dropped into the plasma or serum layer 90, will sink therethrough
to occupy and close the sleeve opening 74 and substantially prevent
the flow of said plasma or serum layer therefrom upon removal as
described of the sleeve 66 from the tube 64. More sturdy closure of
the opening 74 may, of course, be readily effected by attachment as
described of the threaded cover 86 to the lower end of the sleeve
66.
Although disclosed hereinabove by way of illustration as directed
to the provision of a satisfactory physical and chemical barrier
between the respective separated plasma or serum and packed cells
layers of centrifuged blood samples as an adjunct to the automated
analysis of the latter, it is believed clear that the method and
apparatus of the invention would be equally applicable to the
provision of such barrier in a wide variety of fluids having one or
more relative sharp density gradients.
While I have shown and described the preferred embodiment of my
invention, it will be understood that the invention may be embodied
otherwise than as herein specifically illustrated or described, and
that certain changes in the form and arrangement of parts and in
the specific manner of practicing the invention may be made without
departing from the underlying idea or principles of this invention
within the scope of the appended claims.
* * * * *