Isolation tube with an endcap

A method using an assembly, the assembly comprising a separation container comprising a body, the body defining an internal chamber, wherein the body defines an opening at a first end, and wherein the body is configured to receive a sample within the internal chamber, the separation container further comprising a seal attached to the body and disposed across the opening, wherein the seal is configured to seal the opening of the body;

• the assembly further comprising an end cap;
• the method comprising:
• releasably engaging the end cap with the body such that the seal is disposed between the end cap and the body, wherein the end cap is configured to prevent the seal from detaching from the body during centrifugation;
• centrifuging the assembly;
• disengaging the end cap from the body;
• and
• opening the seal.