Liquid purification or separation – Flow – fluid pressure or material level – responsive – Float
Patent
1996-08-09
1998-04-07
Drodge, Joseph W.
Liquid purification or separation
Flow, fluid pressure or material level, responsive
Float
210222, 210514, 210541, 210789, 422101, B01D 2126, B01D 17038
Patent
active
057360332
DESCRIPTION:
BRIEF SUMMARY
This Application is a 371 of International Patent Application PCT/US95/16133, filed on Dec. 13, 1995.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is related to methods and apparatus to separate, and isolate for testing, serum or plasma, red cells, and white cells in evacuated blood collection tubes; obtaining oil free plasma or serum; and harvesting of white cells.
2. Brief Description of the Prior Art
Human blood is routinely collected in sealed, evacuated test tubes and centrifuged to separate the lighter serum or plasma portion from the heavier red blood cells. Typically a portion of the serum or plasma is then removed and tested. While the separated blood is stored awaiting testing certain chemicals can migrate between the separated layers giving incorrect test results. Consequently, the art has developed a variety of separators having a specific gravity between the serum or plasma and the red blood cells. These separators are either solid devices or gels.
The first solid separator was disclosed in U.S. Pat. No. 3,508,653 to Coleman. That device was a rubber or other elastomeric cylinder. A major problem with that device was the inability to maintain a seal because it is costly to maintain the precise inner diameter of the test tube when mass produced. The separator of Lawhead's U.S. Pat. No. 3,814,248 was the next solid separator development following Coleman's invention. Lawhead's separator is a centrifugally motivated spool originating from and placed adjacent to a vacuum maintaining stopper. There is also a polystyrene sphere free and unconstricted within the hollow inside of the tube. In use, blood is collected in the tube and is centrifuged. That action induces the free sphere to move under centrifugal force to join the socket-like underside of the floating rubber spool at the interface of the heavy and light phases. This product was unable to be used for the harvesting of serum because the floating ball frequently became enmeshed in the clot, preventing enclosure of the valve-like separator. Further, the separator did not seal firmly enough to withstand more than mild shock to the tube of separated blood, resulting in remixing of plasma and cells during transport, and other handling.
Ayres' U.S. Pat. No. 3,779,383 describes a complicated, costly device in which the blood introduction end of the tube is opposite to the movable separator end of the tube, and abutting an impenetrable rubber closure. Ayres' embodiment was unable to provide interface separation of the light and heavy phases of the blood because the separation element did not possess a specific gravity intermediate the two phases, but relied on an arbitrary stop element molded into the collection tube, combined with a centrifugally operated element having a specific gravity considerably higher than the blood cells. Blaivas was issued U.S. Pat. No. 3,786,985 for a device very similar to the Ayres' collection tube, excepting that the centrifugally motivated separator element abutted the needle penetrable stopper.
North in U.S. Pat. No. 3,931,018 discloses a solid separator for use in separation of blood serum and blood plasma using centrifugal force that must be inserted into the blood collection tube after blood collection. This device has a disc filter element above the solid separator having a specific gravity intermediate the light and heavy phases. The product has not attained significant acceptance because it is less convenient and less efficient to use and compromises sterility. Others have made centrifugally motivated solid separator devices of various configurations including a hollow, piston like, coaxial tube disclosed in U.S. Pat. No. 4,159,896 to Levine et at., or ring disclosed in U.S. Pat. No. 5,236,604 to Fiehler, a closed end coaxial tube disclosed in U.S. Pat. No., 4,946,601 to Fiehler, an umbrella shaped solid separator device designated to ascend to the interface during centrifugation disclosed in U.S. Pat. No. 4,152,270 to Cornell, and a dual component assembly having a rigid conical core
REFERENCES:
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"A rapid tecnique for the preparation of cell-free blood serum plasma" by H. Harold Nishi, Clin. Chim. Acta 11, (1965), Table of Contents, pp. 290,292.
"New Hydrophilic Polyester-Ester-Amide Block Copolymers" by D. G. Davis and J. B. Conkey, Presented at the Annual Technical meeting of SPE, 1992, pp. 622-627 and attachments.
Atochem Brochure entitled PEBAX Polyether block amide . . . a unique family of engineering thermoplastic elastimers, undated.
Coleman Charles M.
Kendrick William G.
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