A DEVICE FOR THE SEPARATION OF THE LIGHTER FRACTION FROM THE HEAVIER FRACTION OF A LIQUID SAMPLE

Abstract: A device for the separation of the lighter fraction from the heavier fraction of a liquid sample for use with two evacuated receptacles includes a housing having an interior cavity and a membrane separator dividing this cavity into a first portion and a second portion. The membrane separator has a porosity selected for the desired separation thereacross. An inlet struc­ ture is provided for fluid communication between the first por­ tion of the interior cavity and the source of the liquid sample. First structure is provided to allow fluid communication between the first portion of the interior cavity and the first evacuated receptacle. This first structure is opposed from the inlet structure so that liquid passing from the inlet to the first structure travels in a direction along the surface of the mem­ brane. Further structure is provided to allow fluid communica­ tion between the second portion of the interior cavity and the second evacuated receptacle.

Description: The present invention relates to a device for the separation of the lighter fraction from the heavier fraction of a liquid sample according the preamble of claim 1. More particularly this invention relates to a self-contained device for the separation of the liquid component from the cellular component of a blood sample without the use of a centrifuge, an auxiliary circulating system, an auxiliary pump or the like. A common method of obtaining a blood sample involves the use of a two-cannula needle assembly and an evacuated glass tube having a pierceable stopper. The method involves inserting one cannula of the needle assembly into the subject's vein and piercing the stopper of the evacuated glass tube with the other cannula of the needle assembly, thereby establishing fluid communication between the vein and the interior of the glass tube. Due to the lower pressures within the evacuated glass tube blood is drawn from the subject into the tube. Evacuated tubes and needle assemblies for use therewith are described in U.S. Patent No. 3,469,572. Such devices are commercially available under the VACUTAINER Brand name from Becton, Dickinson and Company, Paramus, New Jersey. The blood sample, in the evacuated glass tube, may then be placed in a centrifuge and centrifuged until the more dense cellular component of the blood sample is driven to the bottom of the tube and the less dense plasma is positioned at the top of the sample. The stopper from the tube may then be removed and the plasma sample poured off for subsequent testing. If serum is desired the blood sample is allowed to clot before centrifuging the blood sample. U.S. Patent No. 4,057,499 to Buono teaches the collection of a plasma or serum sample using a sampling member having a hollow interior for the collection of liquid and a piston connected to one end of the sampling member. The piston includes a lip for forming a seal with the interior walls of the sample containing glass tube and an interior portion contains a filter and a one-way valve. In use, a blood sample, in a glass tube, is centrifuged to separate the liquid and the cellular phases and then the device of Buono is placed in the tube and forced along the inner tube surface so that the piston passes through the liquid portion of the sample forcing the liquid portion through the filter and through the valve into the hollow interior of the device. The device containing a portion of the liquid sample is then removed from the glass tube. Buono teaches that it is desirable to physically separate the liquid phase of the sample from the cellular phase to prevent deleterious chemical interaction between the two. Accordingly, Buono teaches the use of a centrifuge and a separate filtering apparatus to obtain the plasma or serum sample. It is believed that forcing a filter membrane through a blood sample, without the use of a centrifuge, is not a practical method of separating the liquid and the cellular components because the filter membrane would soon become caked with the cellular components and unable to perform its task as a filter. Accordingly, it is believed that if the liquid phase of the blood sample is to be filtered from the cellular portion of the blood sample, without the use of a centrifuge, a cross-flow filter arrangement should be provided. In a cross-flow arrangement, the blood sample flows across the surface of the filter membrane in a direction parallel to the major axis of the membrane while a secondary force provides a pressure differential between the blood side of the membrane and the liquid side so that the liquid phase will pass through the membrane. The cross-flow method of filtration is superior because when the blood sample is caused to flow in parallel relationship across the filter membrane there is substantially less tendency for the membrane to be clogged by the cellular portion of the blood sample and therefore allowing the blood to be filtered without the use of a centrifuge. U.S. Patent Nos. 3,211,645; 4,191,182; 4,212,742 and 4,343,705 teach various devices for the filtration of liquid using a cross-flow technique. In each of these patents, the devices utilized require an applied pressure driving force from a separate source across the membrane filter in order to bring about the proper separation. That is, a separate pumping and/or circulating device must be used in conjunction with the cross-flow filter of the known devices. From US-A-3 705 100, from which claim 1 starts, there is known a blood fractionating apparatus of the cross-flow filter type comprising two receptacles for collecting the different blood fractions. The apparatus includes a housing with an interior cavity divided by a separator (filtering) membrane into a first portion and a second portion. The liquid sample is stored in a syringe attached by means of a Luer lock fastening means to the housing for providing fluid communication via an inlet port between the first portion of the cavity and the liquid sample. Outlet ports or first and second communication means, respectively, are provided for fluid communication between the first and second portions of the cavity and the first and second receptacles. The liquid sample to be fractionated under pressure flows along and through the filtering membrane in order to filter the liquid. The fractions flow via the outlet ports out of the portions of the cavity of the housing into the first or second receptacles, respectively. Blood fractionating by means of the known apparatus is rather fussy since the liquid sample at first must be sucked into the hypodermic syringe and, thereafter, injected into the housing for fractionating the blood. This can consume valuable time in emergency situations wherein the liquid phase of the patient's blood sample must be analysed properly in order to diagnose the problem and/or to provide proper emergency treatment. In these situations, it is desirable to provide a device for the separation of the liquid phase of the blood sample from the cellular phase immediately upon the drawing of the blood sample without further steps. Furthermore, in the known apparatus the common evacuated blood collection receptacles can not be used. From EP-A-0 184 852 the priority date of which is prior to while the publication date is later than the priority date of the instant application, a device for fractionating blood is known which includes a receptacle with two evacuated chambers. Within the receptacle there is provided a separation assembly consisting of two spaced opposed walls and a cavity therebetween devided by a separator membrane into two portion. Each evacuated chamber is connected to one portion of the cavity. The receptacle is closed by a pierceable stopper also closing an inlet means of the cavity. When piercing the stopper by means of a twocannula blood connection needle assembly, the blood is sucked into the cavity with the plasma being collected in the one evacuated chamber while the cellular components being collected in the other chamber. It is the object of the invention to provide an operable device for the separation of the lighter fraction from the heavier fraction of a liquid sample, in which device isolated quantities of the separated fractions of the liquid are promptly produced in a simple manner. According to the invention this object is solved by the device comprising the features mentioned in claim 1. Preferred embodiments of the invention are characterized by the features of the subclaims. In accordance with the present invention the device includes two rigid evacuated receptacles each receptacle comprising an open end and a pierceable stopper sealing the open end. Furthermore, the device includes a housing having an interior cavity and a membrane separator deviding the cavity into a first portion and a second portion. Also included are an inlet means for providing fluid communication between the first portion and the source of liquid sample and a first communication means for providing fluid communication between the first portion and the first evacuated receptacle. The first communication means is opposed from the inlet means so that liquid passing from the inlet means to the first communication means travels in a direction along the surface of the membrane. Second communication means for providing fluid communication between the second portion and the second evacuated receptacle are also provided. The two receptacles are held in a fixed relationship with respect to each other by means of a holding means. The holding means cooperates with a coordinating means located between the housing and the holding means in order to facilitate the controlled movement of the evacuated receptacles into engagement and fluid communication with said first communication means and said second communication means. When the inlet means is in fluid communication with the source of liquid sample and the first communication means is in fluid communication with the first evacuated receptacle, and the second communication means is in fluid communication with the second evacuated receptacle, the liquid flows through the inlet means along the membrane through the first communication means into the first evacuated receptacle, and, simultaneously, the lighter fraction is drawn through the membrane and the second communication means into the second evacuated receptacle. The holding means and the coordinating means facilitate simultaneous establishment of the fluid connections between the two evacuated receptacles and the two communication means. Therefore, the possibiliy is avoided that one evacuated receptacle, inserted without the other, will loose a small portion of its vacuum force by drawing some environmental air through the membrane out of the other portion of the cavity before the blood covers the membrane. In case of using the device according to the invention for separating plasma from a blood sample, due to the vacuum forces of the evacuated receptacles, blood is drawn through the inlet means along the membrane through the first communication means into the first evacuated receptacle, while, simultaneously, the plasma is drawn through the membrane and second communication means into the second evacuated receptacle. Therefore, in the second evacuated receptacle plasma is collected, while in the first evacuated receptacle the heavier cellular component of the blood is collected. In accordance with the principles of the present invention, a number of advantages are achieved. Primarily, the present invention provides a simple, straightforward, reliable, easily fabricated device for the separation of the lighter fraction from the heavier fraction of a liquid sample which will operate without the use of additional equipment such as centrifuges and pumps, to promptly produce an isolated quantity of the lighter fraction of the liquid sample. Also, the present invention provides greater flexibility in optimizing the efficiency of the separation process by allowing the use of two evacuated receptacles which may be varied as to size and degree of evacuation. Hereinbelow preferred embodiments of the invention will be described in detail in connection with the Figures attached hereto. Fig. 1 is a side elevation view representing a known blood collection needle assembly; Fig. 2 is a partial cross-sectional view of the needle assembly of Fig. 1 illustrating the second cannula and the internal structure of the resilient sleeve; Fig. 3 is a side elevation view of a known and used evacuated blood collection tube; Fig. 4 is a cross-sectional view of the evacuated tube of Fig. 3 taken along line 4-4; Fig. 5 is a partial cross-sectional view illustrating the interaction between the needle assembly of Fig. 1 and the evacuated tube of Fig. 3 when the second cannula of the needle assembly pierces the stopper of the evacuated tube; Fig. 6 is a perspective view of a device for separation of plasma from a blood sample by means of which the inner structure of a preferred embodiment of the invention is explained in detail; Fig. 7 is a top plan view of the device of Fig. 6; Fig. 8 is a side elevation view of the device of Fig. 6; Fig. 9 is a cross-sectional view of the device of Fig. 7 taken along line 9-9; Fig. 10 is a cross-sectional view of the device of Fig. 7 taken along line 10-10; Fig. 11 is a cross-sectional view of the device of Fig. 8 taken along line 11-11; Fig. 12 is a bottom plan view of the upper housing portion of the device of Fig. 6 illustrating the membrane separator attached to the upper housing portion; Fig. 13 is a bottom plan view of the upper housing portion of the device of Fig. 6, similar to the view of Fig. 12 but without the membrane separator; Fig. 14 is a cross-sectional view of the device of Fig. 8 taken along line 14-14; Fig. 15 is a top plan view of the device of Fig. 6 in use with evacuated tubes, taking a blood sample; Fig. 16 is a side elevation view of the device or Fig. 15, in use taking a blood sample; Fig. 17 is a partial cross-sectional view of the device of Fig. 15 taken substantially along line 17-17; Fig. 18 is a cross-sectional view of the device of Fig. 15 taken along line 18-18; Fig. 19 is a perspective view of the preferred embodiment of the device for separation of plasma from a blood sample whose inner structur is shown in Figures 6 to 18; Fig. 20 is a perspective view of a holding clap, with two evacuated tubes, for use with the device of Fig. 19; Fig. 21 is an end elevation view of the holding clamp of Fig. 20 illustrated without the evacuated tubes; Fig. 22 is an end elevation view of the holding clamp of Fig. 21 illustrated in an open position; Fig. 23 is a perspective view of another alternative embodiment of the preferred device for separation of plasma from a blood sample; Fig. 24 is a side elevation view of the device of Fig. 23 partially cross-sectioned to illustrate the structure surrounding the second needle cannula; Adverting to Figs. 1-5, known prior art blood collection devices include a blood collection needle 30 and a blood collection evacuated glass tube 31. The blood collection tube includes a cylindrical glass body 32 with closed end 34 and neck portion 35. The neck portion is sealed by a resilient pierceable stopper 37 which is applied to the tube while both components are in a reduced pressure environment so that the interior portion 38 has an absolute internal pressure less than atmospheric pressure. The blood collection needle includes a hub 36, a first cannula 39 adapted to pierce a patient's flesh and enter a blood containing vein therein. Second cannula 40 is adapted to pierce stopper 37 to establish fluid communication between the patient's vein and the interior of the evacuated glass tube so that a blood sample is drawn from the patient into the tube. The first cannula and second cannula of the blood collection needle may be separate cannulas in fluid communication with each other through the hub or they may be part of one cannula which passes through the hub. Some blood collection needles include a resilient sleeve which prevents blood from leaving the blood collection needle after venipuncture. A resilient sleeve 41 includes a closed end 42 which is adapted to be pierced by second cannula 40 upon the application of external force to the sleeve in the direction along longitudinal axis of cannula 40. This force can be applied by forcing the blood collection tube stopper onto the second cannula, as best illustrated in Fig. 5. After the blood sample is taken, the evacuated tube is removed from the blood collection needle and the resilient sleeve returns to its original position which allows it to prevent further blood from leaving the blood collection needle. It can be seen that this type of needle assembly will allow several tube samples to be taken from the same venipuncture because the second cannula is sealed after each tube is removed therefrom. Blood collection needle hubs commonly have external threads (not shown) to interact with a tube holder (not shown) to facilitate guiding the tube toward the second cannula so that the cannula pierces the central, thinner, portion of the stopper. The blood sample, in the evacuated tube, may be placed in a centrifuge (not shown) and spun until the more dense cellular component of the blood sample is driven to the closed end portion of the tube and the less dense plasma is positioned above the cellular component closer to the neck portion. The stopper from the tube may then be removed and the plasma poured off for subsequent testing. Also, serum may be obtained by allowing the blood sample to coagulate before centrifuging the blood sample. The serum or plasma produced is used in various types of blood testing equipment which analyze the contents thereof to provide data with respect to the state of the patient's blood. In Figs. 6-14 the construction of the housing of the preferred device 90 for separation of plasma from a blood sample (Fig. 19) for use with two evacuated receptacles, such as the blood collection evacuated glass tubes hereinabove described, is shown. The housing 47 comprising upper housing portion 48 and lower housing portion 49 joined along line 50 to form an interior cavity 51. The housing of Figs. 6-18 is provided with co-ordinating means, as described in detail in Fig. 19, for cooperation with a holding means for the receptacles, as is described in Figs 20-22. A membrane separator 52 divides interior cavity 51 into a first blood receiving portion 54 and a second plasma receiving portion 55. Membrane separator 52 is attached to upper housing portion 48 along sealing area 57 of the upper housing portion, via heat sealing, ultrasonic welding, solvent adhesive or other suitable means, so that fluid passing from blood receiving portion 54 to plasma receiving portion 55 must pass through membrane separator 52. It will be apparent to one skilled in the art that there are numerous constructions which will allow the separation of housing portions by a membrane, for example, clamping the membrane between the housing portions, and that the structure recited hereinabove is exemplary of these many possibilities. An injection cannula 58 having a lumen 59 therethrough is attached to a hollow hub portion 60 of the lower housing portion via adhesive or other suitable means. Lower housing portion 49 also includes an inlet conduit 6; providing fluid communication between lumen 59 and blood receiving portion 54. The injection cannula includes a sharpened distal tip 66 adapted to pierce the subject's flesh and enter a vein therein to provide the blood sample. It is within the purview of the present invention to include a structure wherein the injection cannula is separated from the housing portion by a length of flexible tubing so that the housing portion need not be positioned at the injection site but may be conveniently placed closely thereto. A blood communication conduit 62 communicates between blood receiving portion 54 and upper housing portion 48. The blood communication conduit is opposed from inlet conduit 61 so that blood passing from the inlet conduit to the blood communicating conduit travels in a direction along the length of membrane separator 52 to establish a cross-flow relationship between the blood and the membrane. A first needle cannula 63 is mounted in the upper housing portion at hub 64 via adhesive or other suitable means. Cannula 63 includes lumen 65 which is in fluid communication with blood communication conduit 62. First needle cannula 63 also includes sharpened tip 67 adapted to pierce the stopper of an evacuated blood collection tube. A second needle cannula 69 having a lumen 70 therethrough is attached to a second hub portion 71 of the upper housing portion via adhesive or other suitable means. The second needle cannula includes a sharpened tip 72 adapted to pierce the stopper of an evacuated blood collection tube. The upper housing portion 48 also includes a plasma communication conduit 68 which allows fluid communication between the lumen of the second needle cannula 69 and plasma receiving portion 55 of the housing. In order to support membrane 52 when vacuum forces are applied, as will be explained in more detail hereinafter, support ribs 74 are provided in plasma receiving portion 55 of the upper housing. In the preferred embodiment these ribs are arranged in a parallel arrangement with recesses 75 adjacent to the support ribs for allowing the flow of plasma from the membrane to plasma communication conduit 68. In the preferred embodiment the ribs are formed integrally with the upper housing portion. It is within the purview of the present invention to include other structures to support the membrane against the vacuum forces. These other structures include, but are not limited to: a separate panel, having raised surfaces, inserted in the upper housing portion; a structural screen supporting the membrane; and structural material laminated to the membrane and heat sealed to the housing portion. Figs. 15-18 depict the device for the separation of plasma from a blood sample in use. Initially, injection cannula 58 is inserted through the skin S of a mammalian body M so that lumen 59 thereof is in fluid communication with the blood B in vein V. Immediately after the fluid communication with the vein is established, a rigid evacuated blood collection tube 77 having a pierceable stopper 78 is guided along upper housing portion 48 so that firsk needle cannula pierces stopper 78 so that there is fluid communication between interior 79 of the blood collection tube and the lumen of cannula 63. Simultaneously, a rigid evacuated collection tube 80 is guided along upper housing portion 48 so that second needle cannula 69 pierces a stopper 81 of the evacuated collection tube and there is fluid communication between interior 82 and the lumen of cannula 69. It should be noted that it is desirable that evacuated blood collection tube 77 and evacuated blood collection tube 80 should be guided onto the device substantially simultaneously so that fluid communication between the respective cannulas and tubes is substantially simultaneous. When using a membrane having large pores, the simultaneous connection of the tubes avoids the possibility that one tube, inserted without the other, will lose a small portion of its vacuum force by drawing some environmental air through the membrane before the blood covers the membrane. This potential problem can also be avoided by pre-wetting the membrane with glycerol, saline solution or the like. With the evacuated tubes connected to the device, as best illustrated in Figs. 17 and 18, evacuated blood collection tube 77 creates a vacuum force within the housing which draws blood from vein V through lumen 59 of cannula 58, through blood receiving portion 54 along the surface of membrane 52 and, finally, through blood communicating conduit 62, lumen 65 of needle cannula 63 and into the blood collection tube 77. At the same time that the blood collection tube 77 is drawing blood through the device, evacuated collection tube 80 is providing a vacuum force on the side of membrane 52 opposite from the blood supply. The vacuum force created by collection tube 80 causes plasma from the stream of blood flowing through blood receiving portion 54 to cross through membrane 52 into plasma receiving portion 55 of the housing. The plasma is guided along the housing by support ribs 74, through plasma communication conduit 68 and the lumen of second needle cannula 69 into collection tube 80. When the pressure inside the collection tubes is approximately equal to the blood pressure of the subject, evacuated collection tube 80 will contain a quantity of plasma, separated from the blood, ready for use. Further, blood collection tube 77 will contain a quantity of blood, still containing plasma, which may be held aside pending the outcome of the analysis of the plasma from tube 80. An advantage of the present invention is that it produces samples in two separate tubes. Accordingly, each tube can be sent to a different physical area for storage and/or testing as opposed to separation processes where the plasma and the remaining portion of the blood are contained in the same tube. Also, an important feature of the instant invention is that it allows the use of two separate vacuum sources, thus allowing the use of a wide variety of evacuated tubes having various volumes and degrees of evacuation. This feature greatly increases the flexibility of the instant invention with respect to optimizing the efficiency of the separation process. For example, differential pressure across the membrane can be varied using evacuated tubes having different degrees of evacuation. This is an advantage over systems driven by a single source of vacuum or pressure. Membrane separator 52 is constructed so that it contains pores having a diameter selected so that plasma from a blood sample can flow through the membrane while the cellular components of the blood sample are too large to pass therethrough. It is desirable to use a membrane having a pore size within the range of between about 0.2 and 1.5 micrometers. It is preferred that the membrane has a pore size within the range of between about 0.4 and 0.6 micrometer If additional plasma or serum is required, depending on the time element, blood collection tube 77 may be spun, in a centrifuge, to provide this additional fluid. Accordingly, a blood collection tube containing anticoagulant may be chosen so that the blood sample does not clot and plasma may still be obtained. Also, a blood collection tube containing a separator gel may be used. This latter type of tube may be centrifuged immediately, causing the gel to move to a position between the cellular mass and the plasma, thus preserving the sample for later use. In the preferred device injection cannula 58, first needle cannula 63 and second needle cannula 69 can be chosen from the range of sizes of commercially available blood collection needles. It is preferred that injection cannula 58 be within the range of about 20 gauge to 22 gauge and have a length within the range of about 25 mm to 38 mm (one to 1.5 inches). The first and second needle cannula are preferably within the range of about 20 gauge to 22 gauge and having a length of about 16 mm (0.635 inches). A wide range of membrane sizes can be used with the present invention, depending on the variables associated with the various other elements. With respect to plasma separation, a membrane having an area within the range of about 11 cm² to 32 cm² is desirable when using commercially available evacuated tubes. In the preferred embodiment the membrane separator is sized so that approximately 11 cm² of area is available for transfer of plasma from the blood receiving portion 54 to plasma receiving portion 55. Also, it is desirable that the ratio of length to width be in the range of about 4/1 to 10/1. It should be noted that the volume of the empty space within the interior cavity of the housing, the inlet conduit, the blood communication conduit and the plasma communication conduit must be held to the lowest possible practical value to minimize the amount of air that will be drawn into the evacuated tubes in order to fill this empty space with blood or plasma. This air, when it enters the evacuated tubes, reduces the amount of vacuum force available for drawing and separating the blood sample. Although the above device is described using a membrane suitable for separating plasma from whole blood, it is within the purview of the instant invention to include embodiments suitable for separating light and heavy components of other fluids, such as separating a liquid portion from a colloidal suspension or separating small molecular species from a blood sample. Accordingly, membranes such as known ultrafiltration membranes and known non-woven membranes having suitable pore ratings may be used as components of the instant invention for separating the light and heavy components of a liquid sample. In connection with the housing 91 of the device 90 shown in Figs. 19-22 and functioning in a substantially similar manner as the device 45 (Figs. 6-18) hereinabove described, a preferred embodiment of the invention provided with holding means and coordinating means is explained in detail. The housing 91 includes injection cannula 92, first needle cannula (not shown) covered by first resilient sleeve 94, and second needle cannula (not shown) covered by second resilient sleeve 95. Sleeve 94 includes closed end 96 which is adapted to be pierced by the first injection cannula upon the application of external force to the sleeve in a direction along the cannula toward upright wall 97 of the housing to allow fluid passage through the first needle cannula. Sleeve 94 will return to its original position upon termination of the external force. Likewise, second resilient sleeve 95 includes closed end 99 which is adapted to be pierced by the second needle cannula upon the application of an external force to the second resilient sleeve along the second needle cannula in a direction toward upright wall 97, thus allowing fluid passage through the second needle cannula. Second resilient sleeve will return to its original position upon termination of the external force. Housing 91 includes planar surface 100 having dove-tail guide groove 101 formed therein. It should be noted that the first needle cannula and the second needle cannula are positioned in a substantially parallel relationship. Further, dove-tail groove 101 originates at end 103 of the housing and runs along planar surface 100 in a direction which is substantially parallel to the longitudinal axes of the first and second needle cannula. Also included is holding clamp 102 for releasably holding evacuated tubes 115 and 116 having resilient stoppers 119 and 120, respectively. Clamp 102 includes upper portion 104 and lower portion 105 joined at a hinge 107. The upper portion of the holding clamp includes locking pin 108 which is adapted to engage aperture 109 in the lower portion. Locking pin 108 engages aperture 109 in a snap-fit locking arrangement so that force is required for disengagement. Upper portion includes circularly shaped recesses 110 and 111 having a coordinated relationship with circularly shaped recesses 112 and 114 in the lower portion so that when evacuated tubes 115 and 116 are placed in recesses 112 and 114 and the upper portion is hinged shut so that locking pin 108 engages aperture 109, the tubes will be held in a parallel relationship, as best illustrated in Fig. 20. Holding clamp 102 also includes dove-tail guide projection 117 projecting outwardly from bottom surface 118 of lower portion 105. Dove-tail guide projection 117 is adapted to cooperatively engage dove-tail guide groove 101 and slide freely therein. In using the device the operator places evacuated tubes in holding clamp 102 and closes the locking clamp so that the tubes are held therein. The operator then engages the dove-tail guide projection of holding clamp 102 into the dove-tail guide groove 101 of the housing and slides the clamp toward the needle cannula but does not allow the cannula to pierce the stoppers of the evacuated tubes. At this point, the injection cannula is inserted into the subject to achieve venipuncture and the holding clamp is moved in a direction toward upright wall 97 of the housing to cause the needle cannula to pierce resilient sleeves 94 and 95 and the resilient stoppers 119 and 120 to cause fluid communication between the evacuated tubes and the needle cannula. It may be desirable to only form the dove-tail groove in an area near the first and second needle cannula and to provide an enlarged entrance means at the end of the groove furthest from the cannula, so that the dove-tail guide projection of the clamp may be engaged in the dove-tail groove at a point intermediate the ends of the planar surface rather than at the end thereof. The holding clamp allows the evacuated tubes to be clamped in a parallel relationship and guided toward the injection cannulas so that both resilient stoppers will be pierced by the respective cannula simultaneously. The device also provides resilient sleeves to prevent fluid from passing through the injection cannula. It should be noted that these features, are independent features and are not dependent on each other for function. Accordingly, it is within the purview of this invention to provide a device having a holding clamp with coordinating means and, optionally, resilient sleeves. Referring now to Figs. 23 and 24, another alternative embodiment of the present device functions in substantially the same manner as the above-described preferred embodiment. This embodiment includes housing 124 having injection cannula 125, first needle cannula 127 and second needle cannula 128. This embodiment differs from previously described embodiments in that housing 124 includes frusto-conically shaped recesses 129 and 130 concentrically positioned around the first and second needle cannula, respectively. The purpose of recesses 128 and 129 is to provide a surface to guide the pierceable stopper (not shown) of the evacuated glass tube (not shown) into engagement with the needle cannula so that the needle cannula pierces the central, thinner, portion of the pierceable stopper. With the frustoconically shaped recesses functioning as a guide means for the evacuated tubes, the operator can more easily engage the evacuated tubes with the device. It should be noted that there are many possible combinations for positioning the injection cannula and the first needle cannula and the second needle cannula, and that the embodiments described herein represent only a few of the many possibilities. The housing of the present invention may be constructed of a wide variety of materials such as metals, plastics and ceramics. Plastic materials are more desirable because of their ability to be molded into a wide variety of complex shapes and for compatibility with blood. Transparent thermoplastic materials are preferred so that the operability of the device can be observed through the housing walls. A wide variety of metals and plastics are suitable for the various cannula of the present invention, with medical grade stainless steel being preferred. The choice of material for the membrane separator will depend on the composition of the materials being separated and the sizes of the particles which should be effectively blocked from passing through the membrane. Commercially available dialyzing membranes and ultrafiltration membranes may be used. Representative of such membranes are polycarbonate and polyester membranes having a pore size of within the range of between about 0.2 and 1.5 micrometers as manufactured by Nucleopore Corporation of Pleasanton, California, U.S.A. First resilient sleeve 94 and second resilient sleeve 95 are preferably made of self-sealing elastomeric materials such as rubber and thermoplastic elastomers. Holding clamp 102 can be made of a wide variety of rigid materials with thermoplastic materials such as polypropylene being preferred. The use of injection molded thermoplastic, such as polypropylene, allows a design which incorporates hinge 107 as an integral part of the upper and lower portions of the holding clamp. Thus the present invention provides a simple, straightforward, reliable, easily fabricated device for the separation of the lighter fraction from the heavier fraction of a liquid sample which wild operate without the use of additional equipment such as centrifuges and pumps, to promptly produce an isolated quantity of the lighter fraction of the liquid sample. The present invention also provides greater flexibility in optimizing the efficiency of the separation process by allowing the use of two separate evacuated receptacles which may be varied as to size and degree of evacuation.

Claims: Operable device for the separation of the lighter fraction from the heavier fraction of a liquid sample, comprising first and second evacuated rigid receptacles (77,80;115,116) including an open end; a housing (47;91;124) having an interior cavity (51); a separator membrane (52) dividing said cavity (51) into a first portion (54) and a second portion (55), said separator membrane (52) having a porosity selected for the desired separation thereacross; inlet means (61) for providing fluid communication between said first portion (54) and the source of the liquid sample; first communication means (62) for providing fluid communication between said first portion (54) and said first receptacle (77;115), said first communication means (62) being opposed from said inlet means (61) so that liquid passing from said inlet means (61) to said first communication means (62) travels in a direction along the surface of said membrane (62); and second communication means (68) for providing fluid communication between said second portion (55) and said second receptacle (80;116), characterized in that each receptacle (77,80;115,116) includes a pierceable stopper (78,81;119,120) sealably closing said open end, a holding means (102) is provided for holding the first evacuated receptacle (77;115) and the second evacuated receptacle (80; 116) in a fixed relationship with respect to each other, a coordinating means (101,117) between said housing (91) and said holding means (102) is provided to facilitate the controlled movement of the evacuated receptacles (77,80;115,116) into engagement and fluid communication with said first communication means (62) and said second communication means (68), and, when said inlet means (61) is in fluid communication with the source of the liquid sample and said first communication means (62) is in fluid communication with the first evacuated receptacle (77;115) and said second communication means (68) is in fluid communication with the second evacuated receptacle (80;116), the liquid sample flows through said inlet means (61) along said membrane (52) through said first communication means (62) into the first evacuated receptacle (77;1l5), simultaneously, the lighter fraction of the liquid being drawn through said membrane (52) and said second communication means (68) into the second evacuated receptacle (80;116). Device according to claim 1, characterized in that said first communication means (62) includes a first needle cannula (63) and said second communication means (68) includes a second needle cannula (69), each needle cannula (63,69) having a lumen (65;70) therethrough for piercing said pierceable stopper (78;81;119,120) of said respective first and second evacuated receptacle (77;80;115,116) when said first and second receptacles (77,80;115,116) are moved towards said first and second needle cannulas (63,69). Device according to claim 2, characterized in that at least one of said needle cannulas (63,69;127, 128) is covered by a resilient sleeve (94;95) to prevent fluid passage therethrough, adapted to be pierced by said cannula (63,69;127, 128) upon the application of external force to said sleeve (94;95) in a direction along said cannula (63,69;127,128) thus allowing fluid passage therethrough, said sleeve (94;95) further adapted to return to its original position upon termination of the external force. Device according to any one of claims 1 to 3, characterized by guide means (129,130) for guiding said first evacuated receptacle (77;115) so that said first needle cannula (63;127) pierces the pierceable stopper (78:119) of the first evacuated receptacle (80;116) and for guiding said second evacuated receptacle (80;116) so that said second needle cannula (69;128) pierces the pierceable stopper (81;120) of said second evacuated receptacle (80;116). Device according to any one of claims 2 to 4, characterized in that said first needle cannula (63;127) and said second needle cannula (69;128) are positioned in a substantially parallel relationship. Device according to any one of claims 1 to 5, characterized in that said holding means (102) holds said receptacles (77,80;115,116) so that movement of said receptacles (77,80;115,116) toward said first and second needle cannulas (63,69;127, 128;137,138) causes fluid communication between said first communication means (62) and said first receptacle (77;115) and said second communication means (68) and said second receptacle (80;116) substantially simultaneously. Device according to any one of claims 1 to 6, characterized by support means (74) for supporting said membrane (52) against vacuum forces in said second portion (55). Device according to claim 7, characterized in that said support means includes a distributor panel in said second portion (55) adjacent to said membrane (52), said planel having a raised surface for supporting said membrane (52) and recesses adjacent to said raised portion for receiving the lighter fraction of the liquid passing through said membrane and allowing the lighter fraction to pass to said second communication means (62). Device according to claim 8, characterized in that said distributor panel is integral with said housing (47;91;124). Device according to any one of claims 1 to 9, characterized in that said membrane (52) has a pore size within the range of between about 0.2 and 1.5 micrometers. Device according to any one of claims 1 to 10, characterized in that said membrane (52) has a pore size within the range of between about 0.4 and 0.6 micrometer. Device according to any one of claims 1 to 11, characterized in that said membrane (52) is made of material selected from the group consisting of polycarbonate and polyester. Device according to any one of claims 1 to 12, characterized in that said inlet means (61) includes a third needle cannula (58;92;125) having a lumen (59) therethrough and a sharp distal end (66) adapted to pierce the source of the liquid sample to establish fluid communication therewith.

Inventors: OBERHARDT, BRUCE J., PALMER, PHYLLIS J.
Applicants: BECTON, DICKINSON AND COMPANY
Application year: 1986
Main classification: B01D61
IPC codes: B01D61, G01N33, B01D63