| abstract |
A blood collection device includes a tube for receiving a sample of whole blood for centrifugal separation into the lighter phase, plasma or serum, and the heavier cellular phase. The tube has a needle-pierceable stopper at one end for maintaining a negative pressure in the tube. A blood phase partitioning device is disposed within the tube and includes an upper cylinder member and a lower piston member slidable in the upper member. The cylindrical member has a plurality of peripheral holes therein and a specific gravity greater than that of the piston member, with the members together having a specific gravity between that of the lighter phase and that of the heavier phase. A sealant is disposed within and in direct contact with the cylindrical member and has a specific gravity substantially equal to that of the two members together. During centrifugation of the blood, the partitioning device automatically moves to the interface of the two phases, and the members move relative to each other forcing the sealant radially outwardly through the peripheral holes in the cylindrical member and against the inner wall of the tube to provide a permanent partition between the two separated phases. |