Apparatus for rapidly separating blood into filtered fractions

A blood collection and separation system having multi-chamber collection assembly having a longitudinal axis. The assembly in a preferred embodiment is rotatable about its longitudinal axis and an alternate embodiment is rotatable about an axis parallel to its longitudinal axis. A porous separating body at one axial end of one chamber connects with a second chamber and allows flow of the lighter fraction of the blood from the one chamber to the other chamber during centrifugation, but blocks flow of the heavier fraction. Hydrostatic forces are created during centrifugation to cause flow of the lighter fraction through the body into the other chamber. Preferably the surface of the separating body which faces the first chamber slopes away the spinning axis so that centrifugal force tends to dislodge any particles of the heavier fraction which might be lodged on the surface. The assembly of the present invention affords handling of blood for testing or analysis without human exposure to the blood components.

FIELD OF THE INVENTION 
This invention relates to a method and an apparatus for rapidly separating 
blood into red blood cells and filtered serum or plasma, and performing 
examination therewith, and has particular application to separation using 
a centrifuge and a separating device. 
DESCRIPTION OF THE PRIOR ART 
Much of modern analytical medicine relies upon the examination of blood and 
blood components. Blood is commonly drawn by syringe, or into an evacuated 
tube as in FIG. 1, such as a Becton Dickenson Vacutainer.RTM. tube. Many 
specimens are drawn remotely or in physicians offices and are then 
transported to a central analysis site, such as a reference laboratory. 
Others are essentially processed and examined on site in clinics or 
hospitals. In all cases, it is desirable to minimize human contact with 
the sample in order to reduce the risk of infectious disease transmittal. 
The sensitivity of modern analysis equipment also makes it imperative that 
only totally inert materials contact the blood, and that misdiagnosis 
through cross contamination between samples is totally eliminated. 
Commonly used thixotropic gels, as well as fibrin strands in blood 
components can act to compromise the reliability and accuracy of these 
automated analyzers. Further, samples must be prepared for analysis as 
rapidly as possible, particularly in cases of medical emergency (or stat 
processing). 
Separation of the blood into phases is usually a necessary part of the 
analytical procedure. One method of examining blood samples involves 
coagulating of the blood sample and subsequently separating the sample by 
conventional centrifugation into components consisting primarily of 
heavier phase red blood cells and a lighter phase liquid called serum. A 
second method prevents coagulation through the addition of anticoagulants 
to the blood. The blood is then usually separated by centrifugation into 
the heavier red blood cell components and lighter blood plasma. It is 
generally considered important to recover as much of the available 
serum/plasma component as possible for analysis. This is particularly the 
case with pediatric or geriatric patient samples, where frequently only a 
small amount of patient sample can be obtained. In all cases, it is 
critical to the desired examinations that red blood cells are totally 
separated and are not present in either the serum or plasma. It is also 
desirable that the specimen be analyzed as soon as is practical after the 
separation has occurred. 
Conventionally, the process of separation is accomplished in a centrifuge 
which spins the entire sample, contained in a tube, around an axis of 
rotation for approximately 10 to 15 minutes and subjects it to a 
centripetal acceleration of approximately 1200 times gravity. These 
devices require counterbalanced loading, and frequently generate 
considerable amounts of energy since the sample must be cradled in a rotor 
of significant mass which is subject to the same gravitational force as 
the sample. These devices occasionally fail, potentially exposing the user 
to hazardous aerosols generated by the sample. The significant amount of 
spin time required by these devices furthermore generates frictional 
heating of the rotor chamber, which must be overcome either by an 
expensive refrigeration system, or by air cooling of the chamber, which 
again potentially exposes the user to said hazardous aerosols, 
particularly in the event of a rotor failure or tube breakage. 
Once the serum or plasma has been separated, great care must be taken to 
avoid the reintroduction of red blood cells, since this could invalidate 
the examination process. In those cases where blood components are 
analyzed remotely, as with a reference laboratory service, a permanent 
barrier must be established between the separated phases. To address this 
difficulty, a number of methodologies have been devised. On method 
consists of carefully pouring the serum or plasma from the primary 
collection tube into a secondary transport tube. This method exposes the 
clinician to potentially hazardous aerosols of the serum or plasma, does 
not yield all of the available serum or plasma, and risks re-mixing during 
the handling and pouring process. A second method relies on the movement 
of a material with density specifically between that of serum and the 
heavier cell components. This viscous thixotropic gel is specifically 
configured as part of a blood collection tube system. During 
centrifugation of this gel in a blood filled-tube, it migrates to a 
position between the serum (or plasma) and red blood cells (See U.S. Pat. 
Nos. 3,647,070; 3,852,194; 3,986,962; 4,012,325; 4,055,501; 4,083,784; 
4,189,382; and 4,350,593). Since the gels, however, perform no significant 
wiping or filtering action on the sample, fibrin and residual cells (which 
can cling to the tube wall during centrifugation) may remain in the serum 
(or plasma) layer. Furthermore, particles of the gel itself can remain in 
the sample. Modern automated analysis equipment can be caused to 
malfunction through the presence of fibrin or gel particles. These gel 
particles, and in particular the presence of red blood cells can 
furthermore lead to incorrect or misleading test results. In the interest 
of convenience, and because of the need to achieve relatively effective 
barriers between red blood cells and serum or plasma, in spite of their 
shortcomings, gel based serum separation tubes now account for 
approximately 25% of the total blood collection market. 
A further centrifugally activated serum separating concept consists of a 
piston having a specific gravity between serum and red blood cells which 
is fitted into a centrifuge tube. Such devices, some of which include 
combinations of pistons and gels and/or filters, are described by U.S. 
Pat. Nos. 3,909,419; 3,919,085; 3,920,557; 3,926,646; 3,931,018; 
3,951,801; 3,957,654; 4,001,122; 4,088,582; 4,152,270; 4,14,690; 
4,202,769; 4,417,981; 4,425,235; 4,443,345; and 4,492,632. These devices 
are all designed to function in standard centrifuges, and in order to 
effectively perform their wiping action require tight tolerances between 
piston and tube, resulting in relatively high costs. Indeed, these devices 
have found only very modest market acceptance. 
Other methods, such as described by U.S. Pat. No. 4,021,352 attempt to use 
a filter medium to directly achieve the separation of blood into its 
components. The medium described, however, is unable to maintain a 
separation barrier over time since the channel size described permits the 
passage of red blood cells, and the process described in both cumbersome 
and technique-dependant. U.S. Pat. No. 4,639,316 describes a device 
utilizing vacuum pressure preapplied in manufacturing of the blood drawing 
tube to directly filter and separate red blood cells from plasma as part 
of the blood drawing procedure. While the device does not require 
centrifugation, it cannot be used to examine blood serum, and has the 
practical limitation of requiring the blood drawing tube to be attached to 
the patients vein for approximately 30 seconds. Access to the filtered 
plasma would also require greater care than currently necessary in order 
to avoid dripping plasma as the filtering element is removed from the 
processing tube. U.S. Pat. No. 4,946,603 also does not require 
centrifugation, but is described as practical only for separating 0.5 ml 
of blood, too small an amount to be useful for the broad range of 
examinations usually performed. 
U.S. Pat. No. 4,492,634 describes still another method of filtration which 
again relies on conventional centrifugation, but has the added expense of 
a double-stoppered tube, and makes no provision for filter clearing. 
A number of concepts have also been described which aim to achieve filtered 
serum or plasma from separated blood. U.S. Pat. No. 4,369,117 combines the 
previously described idea of a piston with a filtering element. This 
device also functions only in a conventional centrifuge, and is useful 
only for serum separation. In order to minimize clogging problems common 
with filtering devices used to separate blood components, it has a filter 
pore size greater than that of red blood cells. This, however, also allows 
red blood cells to mix with serum, therefore substantially reducing its 
utility. U.S. Pat. No. 4,522,713 describes a similar but more complex 
device, which also requires conventional centrifugation, and has not found 
widespread market acceptance. Among its practical limitations are the 
requirement of separating, by centrifugation, the blood into fractional 
components prior to filtration. At that point, the device must be 
introduced to the centrifuge tube, respun, and with the further constraint 
of a practical limitation of recovering only 50% or less of the available 
fluid (and that only with flat bottom tubes, which are not conventionally 
in use). 
Still other filtration devices such as described by U.S. Pat. Nos. 
4,464,254, and 4,602,995 require separated blood fractions prepared and 
layered by conventional centrifugation and are usually not designed to act 
as permanent barriers between the fractions or to recover all available 
blood serum. An exception is described in U.S. Pat. No. 4,957,637, which 
does claim to create a permanent barrier, but still requires conventional 
centrifugation prior to a separate filtering step. 
U.S. Pat. Nos. 4,828,716 and 4,846,974 describe a system wherein the blood 
collection chamber is rotated about its own axis to effect the separation 
of blood into its components. Such axial separation can reduce the 
processing time to less than 1 minute as compared to the aforementioned 10 
to 15 minutes required by conventional centrifugation. The difficulty with 
this process, however, is the method of achieving phase separation once 
the system comes to rest. In one case, the sample must first be 
transferred from the collection tube into a special, and relatively 
expensive secondary processing cassette, where a gel substance is used to 
create the separation barrier. In the other, a probe is inserted directly 
into the sample chamber, and an elaborate sensing system is employed to 
determine when the separation process has been completed. The probe, of 
course, is a potential source of sample contamination and 
cross-contamination between samples. This has been anticipated by the 
authors, and a further embodiment claims to address this concern with an 
elaborate construction of dual tubes, one way valves, filters, and a 
syringe like action. Both embodiments, however, rely on mechanically 
changing the chamber volume, thereby expressing one of the phases into a 
secondary chamber component, and sensing when the separation interface has 
been reached in order to terminate the process. This procedure is 
inherently unreliable, requires expensive hardware, as well as a new, 
unique, and also expensive blood collection tube. 
Beyond the mechanical elements of blood processing and their inherent 
shortcomings, the current methodologies are also largely labor-intensive, 
and fraught with high potential for error. Modern analyzers have the 
capability to process a very broad range of clinical data on a single 
patient sample in a matter of a few minutes. Current practice, however, is 
to draw substantially more patient sample than is required by these 
analyzers. The samples are then divided into a number of separate aliqots, 
each of which must be separately labelled, often by hand, as well as 
manually transferred into separate and open containers by pipetting. This 
labelling step can lead to human error, resulting in misdiagnosis, while 
the aliquotting step exposes a laboratory technician to the hazard of 
infection from the patient sample. Furthermore, these steps add additional 
processing time and cost. 
There are currently methodologies which propose to utilize the originally 
drawn patient sample tube directly by the analyzer after centrifugation. 
This method, however, still requires drawing substantially more patient 
sample than required for analysis. Furthermore, a method of stopper 
removal or stopper piercing is required in order to access the serum or 
plasma. Once accessed, there is the further complication of avoiding the 
red cell, or gel interface, and subsequent disposal or washing of the 
piercing needle. Finally, a method to avoid spillage or the formation of 
aerosols within the analyzers must be developed. 
SUMMARY OF THE INVENTION 
The invention embodies a separator that can be mounted on a standard blood 
collection tube or syringe, or configured integrally with such a device, 
in order to rapidly achieve filtered and permanently separated blood 
components under the influence of centrifugal acceleration, preferably 
axially-oriented. 
In one embodiment, the stopper is first removed from a standard, blood 
filled collection device, and the separator installed in its place. This 
can be accomplished manually, or automatically by machine in those 
instances when it is desirable to eliminate human exposure to the blood 
sample. The tube and separator assembly is then simply inserted into a 
centrifuge which spins the entire assembly about its own axis, or a remote 
or offset axis substantially parallel to the tube axis, for approximately 
one minute. Radial forces within the system separate the heavier red blood 
cells and move them to the outer tube wall, leaving the lighter serum or 
plasma near the tube's center. These same radial forces also set up 
axially oriented hydrostatic pressure forces which push fluid against the 
separator. 
The separator is a body of a porous material, such as a filter, a membrane 
or a flow restricter, which exhibits a pore size or opening sufficient to 
permit passage of particles of the desired lighter phases, yet restricting 
passage of the heavier red cell components, as well as fibrin and other 
undesired blood components. The shape of the separator can be configured 
so that it has an inclined surface exposed to the collection chamber. The 
more powerful radial forces act to remove red blood cells and fibrin from 
its inclined surface, thereby clearing a path for the hydrostatically 
driven lighter phases to pass through into a secondary collection chamber. 
By utilizing a hydrophobic material, or an appropriately channeled 
geometry within the separator, fluid will only pass through the separator 
under pressure, such as hydrostatic or centrifugally generated, and a 
permanent barrier between the separated and filtered phases can be 
achieved. 
Advantageously, this concept eliminates the need for probes, valves, 
sensors or gels, which can compromise sample integrity and add complexity 
and cost. It is thereby also capable of recovering all available serum or 
plasma. The separator is further capable of acting as a transport tube, as 
well as a self contained dispensing device. The present invention can 
therefore fully accommodate the advantages of today's sophisticated modern 
analyzers by rapid centrifugation (integral to the analyzer if desired), 
by eliminating the need for aliquotting, relabeling, and additional 
handling, and by capturing all available patient serum or plasma and 
presenting it to the analyzer in filtered, pre-measured and easily 
accessible form. This fully integrated system thereby totally automates 
the processing of blood, significantly speeding up the process, while 
eliminating the potential for sample labelling error as well as infection 
of the processing staff.

DETAILED DESCRIPTION 
The present invention relates to a separating device that can be assembled 
with a collection container for use in a centrifuge. When assembled, the 
device provides a pair of chambers within the assembly. Whole blood is 
collected in the first chamber and during the centrifuging, one fraction 
of the blood, for example the serum or plasma passes through the 
separating device into the other chamber. When whole blood has been drawn 
into the blood collection chamber, it can either be allowed to clot 
naturally by waiting approximately 30 minutes, it can be induced to clot 
more rapidly through the addition of clot activators, or it can be 
prevented from clotting through the addition of clot inhibitors. Clotted 
blood yields serum, and unclotted blood yields plasma after separation. 
In the embodiment of the invention illustrated in FIGS. 1 through 8, a 
separating body 7 is mounted in one end of an attachment 8 adapted to fit 
on the open end of a standard collection tube after removal of the stopper 
closure 3. After removing the stopper 3, one end of the attachment 8 may 
be inserted in its place to form an assembly of the tube 2 and the 
attachment 8. 
At its one end, the attachment 8 has a seal 4 into which the open end of 
the tube 2 fits to assure that the blood will not leak from the tube 
during processing. Above the seal 4 the attachment has an outer wall 5 
forming a collection chamber 5a which is closed by a cap 6 fitted on the 
opposite end of the wall 5. Centrally of the seal 4, a porous partition 
body 7 is provided to serve as a separation device between the chamber 5a 
above the seal and the interior chamber 2a of the collection tube. The 
separator 7 is operable to selectively pass fluid fractions with particles 
below a given threshold size. When assembled as shown in FIG. 3, the 
assembly provides a sealed container for the blood 1 collected in the tube 
2. 
It should be noted that in most blood laboratories, the collection tubes 2 
are of standard diameter and thickness so that the attachments 8 for the 
tubes may be interchangeably used with the collection tubes, and adoption 
of the present invention will not require modification of the existing 
blood collection techniques, avoiding the necessity for substantial 
replacement of supplies as is required by the prior art systems described 
above. 
In the preferred embodiment of the invention, the assembly shown in FIG. 3, 
consisting of the collection tube 2 and the attachment 8, is inserted into 
a specially constructed centrifuge as shown diagrammatically in FIG. 4. 
The centrifuge has a drive motor 9 with a central rotor adapted to 
accommodate the assembly of the collection tube 2 and the attachment 8. 
Energization of the motor 9 rotates the assembly and spins the assembly 
about its axis to effect centrifugal separation of the various fractions 
of the blood sample 1 within the center of the tube 2. The speed of 
separation of the fractions is a function of the rotational speed of the 
rotor. The assembly of the attachment 8 and the tube 2 is symmetric about 
its longitudinal axis, and does not require balancing as do tubes spun in 
conventional centrifuges. 
As shown in FIG. 5, as the rotor and the assembly are accelerated, the 
heavier blood components 10 are forced to the outside wall of the blood 
collection tube 2 and the lighter plasma or serum 11 is displaced towards 
the center of the tube. The threshold porosity of the separating body 7 is 
selected to pass the cells of the lighter fraction but to block passage of 
the heavier cells so that the lighter fraction 11 is free to pass through 
the separation device 7 and into the chamber 5a defined by the outer wall 
5 of the attachment 8. The radius of the standard collection tube is on 
the order of 5 mm as compared to a length of approximately 70 mm, radial 
separation of the fractions of the blood samples requires a short path 
length as opposed to the long path length provided when the separation is 
axially of the chamber. Due to the high acceleration and short path 
length, separation is effected in one minute or less. This rapid 
separation process makes the invention ideal for situations when tests 
must be performed very rapidly, such as in stat or emergency situations. 
It should be noted that the wall 5 may be offset outwardly from the wall 2, 
so as to insure that the wall is greater in diameter than the inside 
diameter of the sample in the chamber 2a, so that the centrifugal force on 
the blood sample generates a hydrostatic pressure differential between the 
chambers 2a and 5a, which can act to drive the serum fraction 11 through 
the porous separating body 7 from the chamber 2a into the chamber 5a. This 
is illustrated in FIG. 5. 
As shown in FIG. 5, the porous body 7 has a downwardly facing surface 
facing the chamber 2a in the collection tube. The surface extends across 
the full width of the tube and merges into the seal 4 at the outer wall of 
the collection tube. As shown, the surface 13 is substantially conical and 
starts at the wall of the collection chamber and is inclined relative to 
the radial direction toward the central axis of the collection chamber 2a. 
The inclination of the surface 13, when spun in the centrifuge about its 
axis, throws outwardly any particles of the heavier fraction 10 which are 
above the threshold size of the body 7 and may lodge on the surface 13 as 
the lighter fraction Il flows through the pores into the chamber 5a. This 
self-clearing feature eliminates the clogging problems associated with 
previous attempts to effect simultaneous filtration and separation. Also, 
since the lighter phases are drawn out of the original collection tube, 
the need for wiping red cells, which potentially can create cell damage, 
from the tube walls, as described in prior patents and publications, is 
entirely eliminated. 
FIG. 6 shows how the assembly of the attachment 8 and the tube 2 after 
separation has been completed and just prior to deceleration and stopping 
of the centrifuge. Sensing of the separated phases is not necessary, since 
only light phases such as plasma or serum can pass through the separation 
device. Previously described inventions that rely upon sensing of the 
blood phase interfaces critically require specific placement of all labels 
to assure that the sensing window was not obscured by the label. This 
device, on the other hand, may accept labels that completely cover the 
tube, or that are in any manner randomly applied. Also, since these 
lighter phases are passed through the separation device interiorly through 
hydrostatic pressure, the need for mechanical force or vacuum as described 
by previous inventions is eliminated. This overcomes problems of 
hemolysis, which can occur if delicate blood components are forced to 
separate through mechanical pressure. Also, in systems where there is a 
need to mechanically change the separation chamber volume, it is often 
difficult to recover more than 80% of the available serum or plasma 
volume. This is particularly true when only a small amount of blood is 
available, as is frequently the case with pediatric or geriatric patient 
samples. The curved portion of the collection tube base, or the shape 
constraints of the various separator schemes described in previous patents 
and publications, makes these systems notoriously inefficient, as does the 
need of sensing the phase interface between the blood phases. This 
invention, however, is capable of recovering substantially all available 
serum or plasma. 
FIG. 7 illustrates the position of the fractions upon stopping of the 
centrifugal spinning of the assembly. The separated fluids come to rest as 
shown in FIG. 7. By utilizing a hydrophobic material as part of the porous 
body 7, or by appropriately configuring the geometry of the device, i.e. 
through the inclusion of a serpentine fluid trap, plasma or serum 11 will 
not flow back into the original blood collection chamber 2a, thereby 
effecting a permanent separation without the need for valves or gels as 
described in previous patents and publications. The entire assembly, 
including the blood collection tube 2, may now be shipped to a reference 
lab for processing. Alternatively, the cap 6 may be removed to afford 
removal of all or part of the serum or plasma as aliquots. If desired the 
serum or plasma collection attachment 8 may also be removed from the 
collection tube and the end of the attachment with the separation body 7 
may be covered with a second cap 6 as shown in FIG. 8. This allows direct 
access to the heavier blood components still left in the original blood 
collecting tube and overcomes the deficiencies of other previous 
inventions. The resulting serum or plasma transporting assembly of FIG. 8 
is lighter than blood collection tubes with gels or other internal 
barriers thereby reducing shipping and handling costs. The transport 
assembly illustrated in FIG. 8 can also be configured to resemble a sample 
cup that would make it suitable for direct insertion into an automated 
analyzer, thereby eliminating the need for secondary aliquoting and 
potential human exposure, or error, due to mislabeling or handling. 
Through-the-cover sampling by the analyzer may also be readily 
accomplished in such a system. By utilizing an automated device to remove 
the serum or plasma collection attachment 8 from the blood collection 2, 
the need for human exposure to blood components is also eliminated. 
A second embodiment of the invention is illustrated in FIG. 9 in which a 
pipette tip is provided at the opposite end of the chamber of the 
separation attachment in place of the cap 6 described in the first 
embodiment. In other respects, the attachment is similar to the first 
embodiment. In this embodiment, the attachment is designated 28 and has an 
outer wall 25 defining a collection chamber 25a. At one end, the 
attachment has a seal 24 with a central separation body 27 adapted to 
interfit with the open end of a standard collection tube 2. At the 
opposite end, the cylindrical wall 25 of the attachment 28 tapers to form 
a pipette tip 14 which, when inverted as shown in FIG. 9, affords 
dispensing precisely desired volumes of serum or plasma, once separation 
has been completed, avoiding the need for additional transfer or 
aliquoting steps. The attachment 28 may be used as a transport tube as 
shown in FIG. 10 by providing a cap 26 for the sealing end of the 
attachment. 
Since the devices described herein are extremely simple in construction, 
and do not require complex sensing or mechanical controls, they are also 
inherently very reliable, rugged and cost-effective to produce. In 
particular, this method of processing lends itself to the cost-effective 
construction of an automated centrifuge that can spin multiple tubes 
simultaneously, as shown diagrammatically in FIG. 11. Whereas conventional 
centrifuges normally found in the clinical laboratory can batch-process 
about 60 tubes per each 15-minute run, yielding a throughput of about 240 
tubes per hour, a multiple tube device as shown in FIG. 11, even if 
configured to spin only 10 tubes per one-minute run, could process 400 
tubes even if a generous 30-second loading and unloading period is 
allowed. This centrifuge would be much smaller than a comparable 
conventional centrifuge with corresponding throughput, and since balancing 
is not required, and since tube loading location is always constant, the 
multiple tube device of the present invention would be ideally developed 
into a totally automated centrifugation system. Such a system could 
include loading and unloading of tubes, bar code label identification, as 
well as sensing of sample quality in the collection chamber while the 
device is spinning. Referring to FIG. 11, the centrifuge has a drive motor 
29 which is coupled to a plurality of rotors 30 by a common drive 
mechanism, such as a belt 31. Each rotor is adapted to mount an assembly 
of a collection tube 2 with an attachment 8 and the single drive motor 29 
may be coupled to ten rotors without undue loading of the motor or the 
drive mechanism. 
The invention may also be practiced with a prepackaged blood collection 
syringe or collection tube 32, such as shown in FIG. 12. In this 
embodiment of the invention, the collection tube 32 provides a collection 
chamber 32a which is closed at the top by a stopper 33 which is sealed in 
the open end of the tube 32. The stopper is in three parts, consisting of 
a self-sealing core 15, that can be pierced by the collection needle in a 
similar way to current blood collection tube stoppers. Surrounding the 
core at 15 is a porous separation body 16 similar to the separation body 7 
of the previously-described embodiment. The stopper is covered with a foil 
seal 17 which acts as a vacuum-retention barrier. To draw blood, the foil 
17 is pierced, as is the self-sealing core 15. In order to process the 
sample as described in the previous embodiments of this invention, the 
foil is peeled away, and a serum or plasma collection attachment 38 is 
mounted on the tube 32 as shown in FIG. 13. The attachment 38 has a 
cylindrical wall 35 defining a collection chamber 35a. At one end, the 
wall is capped by a cap 36 and at the other end, an internal seal is 
provided at 34 to seal with the upper end of the collection tube 32. With 
the attachment 38 in place, the assembly is now ready for processing, 
significantly without the need for removal of the stopper or other closure 
and within a closed system. 
Since the volume of the serum or plasma collected in the collection chamber 
35a can be limited by the volume of the chamber, it is now also possible 
to create precisely-measured quantities of plasma or serum for 
presentation to the analyzer, or for interaction with pre-measured test 
reagents for specific diagnostic tests. Other embodiments of the invention 
can therefore also include a device to automatically aliquot specifically 
predetermined test volumes from the spinning assembly into analyzer-ready 
sample cups. 
FIG. 14 illustrates a further embodiment of the invention wherein an 
assembly acts as a self-contained closed system, which could fully 
automate the blood processing process. In this embodiment, the blood is 
collected in the upper part 42 of the assembly which provides a collection 
chamber 42a. The top wall of the upper part of the collection chamber 42a 
has a central self-sealing core 46 which is part of a foil overwrap 
closure 47. The lower end of the chamber 42 is defined by a separation 
body 48 similar to the separators 7 described above. The porous separator 
body 48 is disposed between the upper part 42 and the lower part 45 which 
defines a lower chamber 45a. The lower end of the chamber 45 is closed by 
an easily pierceable membrane or foil 47a. Blood is introduced into the 
collection chamber 42a through the core 46 and the assembly may be spun to 
separate the plasma or serum or other light fractions through the porous 
body 48 into the lower collection chamber 45a. The serum and plasma may be 
withdrawn by piercing the closure 47a and the heavier fractions may be 
withdrawn by piercing the closure 47. 
This device can also be configured to be an analyzer, drawing only as much 
patient blood as needed for analyzer processing. With this reduced volume 
need, it is possible to also eliminate the need for a pre-evacuated 
collection tube, and blood collection into the blood collection chamber 
42a may be achieved by replacing the core 46 with an inlet port 49. A 
suction device 50 is mounted at the lower end of the collection chamber 45 
by a closure element 47b. The suction device 50 may be a simple suction 
bulb to evacuate or reevacuate the chamber 42a and/or generate a negative 
pressure within the chambers 45a and 42a. Since the whole blood does not 
flow through the separation device 48, the lower closure 47b with the 
suction device attached may be removed and replaced with the lower closure 
47a as described above before centrifuging. With the closure 47a in place, 
the assembly may then be inserted in the centrifuge and operated as 
described above in connection with FIG. 14. 
A further embodiment of the invention places the collection assembly offset 
from the axis of rotation as shown in FIG. 16. This system has the 
advantage of requiring substantially lower rotational speed than the above 
systems which spin the collection assembly about its own axis. The 
reduction in rotational speed results from the fact that the centrifugal 
force on the red cellsplasma interface is directly proportional to the 
distance 22 of the interface from the axis of rotation 21. The greater 
this distance 22, the lower the speed requirement for separation. The 
lower speed system of this embodiment can have the effect of reducing 
processing noise and component costs, and can speed up processing time. In 
this embodiment, the geometry or shape of the collection assembly may also 
be designed to take full advantage of the centrifugal and hydrostatic 
pressures created within the system. 
In the illustrated example, the collection assembly consists of two 
separable and adjacent chambers whose geometry is essentially flat rather 
than cylindrical as in most conventional blood collection devices. The 
system has a blood collection chamber 52 having an inner wall 53 adjacent 
the axis of rotation 21 and an outer wall 54 spaced outwardly from the 
inner wall 53. Separator bodies 58 are provided between the walls 53 and 
54 to form the side walls of the chamber 52. The inner wall 53 has an 
inlet port 59 for accessing the collection chamber 52. A plasma collection 
chamber 55 is positioned outwardly of the chamber 52 and extends inwardly 
to surround the side walls of the chamber 52 in the area of the separator 
bodies 58. The chamber 55 has an access port 61 adjacent its outer wall 
62. In operation, the whole blood is drawn into the collection chamber 52 
and upon centrifuging of the assembly, the heavier fraction is displaced 
towards the outer wall 54 and the lighter plasma or serum fraction is 
displaced inwardly and flows through the separation bodies 58 into the 
outer chamber 55 by reason of hydrostatic forces and is displaced toward 
the outer wall 62. As shown in FIG. 16, the heavier fraction 10 remains in 
the chamber 52 whereas the lighter fraction 11 is displaced into the outer 
chamber 55. 
A novel method of blood collection with this assembly may be achieved by 
evacuating the inside of the chambers prior to blood collection. The inlet 
port 59 has a valve 24 which may be operated to connect the inlet port 59 
With the evacuated chambers 52 and 55. By placing the inlet port 59 in 
direct proximity to blood resulting from a skin prick, and subsequently 
opening the valve 24, blood is sucked into the chamber 52 for processing. 
This system is advantageous in designing collection devices specific to 
individual tests or analyses. This configuration of the collection 
assembly enables the outer walls 54 and 62 of the collection chambers 52 
and 55 respectively to be manufactured as flat plates or collection dishes 
and visual analysis of the separated components will be enhanced by 
elimination of the curvature created by cylindrical tubes and chambers to 
facilitate examination. The assembly provides independent access to 
individual sample aliquots. 
In order to facilitate the process of separation, it is also possible to 
add external vacuum forces to the chamber 55, thereby assisting the 
naturally created hydrostatic forces within the system. The port 61 in the 
chamber 55 may also be used to effect evacuation of the serum or plasma 
from the chamber into a separate vessel, thereby further eliminating the 
possibility of backflow of serum or plasma into the blood collection 
chamber 52. 
A further embodiment would integrate the assembly directly into an 
automated analyzer. This would permit the analyzer to accept whole blood 
in a closed system and effect all sample separation and analysis steps 
without human exposure to the blood sample under analysis. The invention 
described herein is not limited to the separation of blood but can 
advantageously be used in the separation of any multiple phase liquid or 
other fluid where separation may be enhanced through the benefits 
described herein. Effectiveness can further be enhanced or customized by 
choice of separation material utilized in the separation bodies. Multiple 
filters or membranes may be layered in the separation body to achieve 
specific goals as dictated by the end use, and multiple second chambers 
may be provided to separate the plasma into individual sample aliquots. 
Further modifications and enhancements of the invention will occur to those 
skilled in the art and are intended to be embraced within the invention as 
defined by the attached claims.