Method for separating serum or plasma from the formed elements of blood

Abstract

A self-contained separator assembly comprises a container having at least one end open which is adapted to receive blood for subsequent separation into a light phase comprising plasma or serum and a heavy phase comprising the formed elements of blood. A closure is sealed into the open end of the container which may be penetrated by a cannula through which blood may be received into the container. A piston-like plug which forms a seal against the container wall is characterized by an average specific gravity so as to permit the plug to be centrifuged through a blood sample toward the interface of the heavy phase and the light phase. The plug comprises a valve seating portion having a valve opening therein and a valve head adapted to seat on the seating portion and bias means extending between the seating portion and the valve head to bias the head to the seated position on the seating portion after centrifugation.