Patent GB-1407267-A (GB)
Title: Apparatus for fluid collection and partitioning
IPC: G01N33/48
Filed: 1972-09-07
Abstract: 1407267 Centrifugal separation CORNING GLASS WORKS 7 Sept 1972 [7 Sept 1971 23 Feb 1972] 41549/72 Heading B2P [Also in Division B8] A spool 32, Fig. 7, for use in an assembly for effecting partitioning of the heavier phase 72 (red blood cells), Fig. 6, from the lighter phase 68 (serum or plasma) of a centrifugally separated fluid specimen (whole blood), at a position not lower than the interface 74 of the fluid phases, within a tubular container 12 comprises a generally cylindrical main body 34 having a central axial orifice 52, a resilient annular wiper portion 38 tapering outwardly away from the upper portion 36 of the body 34 and having an outer surface 42 for sealingly engaging the inner surface of container 12, and an annular shirt portion 48 extending outwardly and downwardly from the lower portion 46 of the body 34 and having a maximum outside diameter less than the outside diameter of the wiper portion 38. The spool may be made of rubber or polystyrene and has a preferred specific gravity of 1.044- 1.055 which lies below that of the red blood cells (1.08-1.09) and above that of blood serum or plasma (1.02-1.03). The spool body may be provided with circumferentially spaced friction nubs 44 and guide nubs 54. The tube 12 which may be made of transparent glass or plastics is closed by a hollow rubber stopper 20 having an internal diaphragm 24 and contains a plug or float member 60 made of the same material and having the same specific gravity as the spool 32. To effect the separation of whole blood, the tube with the spool disposed near its top and the plug 60 resting freely on its bottom is first evacuated and sealed by the stopper 20. One end of a doubleended needle is injected through a patient's vein and the other end is pushed through the diaphragm 24 permitting the vacuum in the tube to draw a blood sample 64 into the tube through the spool orifice 52, Fig. 2, the plug 60 then floating at or near the top of the sample. The tube with its contents is then placed in a centrifuge. After the start of centrifugation, the phases begin to separate and the plug 60 follows the interface as it gradually moves downwardly of the tube. Under the effect of centrifugal force, the spool 32 slides down the tube through the lighter phase which in turn flows up through its central orifice 52 until at the end of centrifugation, Fig. 6, the spool reaches the interface and the plug 60 engages its skirt portion 48 providing a positive seal between the lighter phase 68 and the heavier phase 72. In a modification, Fig. 9, the spool 32a has a more flexible wiper portion 38a of uniform, instead of tapered, cross-section, and has guide nubs 54a only at its top. The tube 12 may be provided with a constriction 17 for engagement with the guide nubs to retain the spool at the top of the tube before a centrifuging operation. In a modification of Fig. 9, Fig. 11 (not shown), for use with a coagulated blood sample the spool has a smaller central orifice which does not require a plug to accomplish partitioning between the phases, this being effected by a natural plug of fibrin which has a specific gravity between those of the phases. In a further modification of Fig. 9, a filter or porous diaphragm 78, Fig. 12, made like a fine screen or a plug of open-celled form, e.g. of polyethylene or polystyrene, is secured within the central orifice 52 of the spool 32c. When treating coagulated blood, the separated fibrin layer will be compacted below the diaphragm.