Plasma separator with barrier to eject sealant

A blood collection and separator assembly capable of separating blood into its component parts of plasma or serum, the light phase, and cellular portion, the heavy phase, is disclosed. The assembly comprises a container having one open end for receiving blood and a two part barrier assembly slidably disposed in the container. The outer part or shell of the latter assembly has a specific gravity greater than the light phase of blood and the inner part or plunger has a specific gravity less than the heavy phase of blood. Interposed between the two parts is a viscous sealant, such as silicone grease. After the blood separates into its light phase and heavy phase under centrifugal force, the barrier assembly is introduced so it sinks to the interface between separated phases. Upon applying further centrifugal force, the inner plunger tends to move upward while the outer shell tends to move downward thus causing a squeezing action on the interposed sealant. This forces the sealant out through ports in the outer shell where it produces a circular impervious barrier between the barrier assembly and the inner walls of the container.