What is the function of the gel in serum separator tubes?

• A. Gel forms a barrier between serum and cells after centrifugation, reducing carryover and improving sample stability
• B. Gel reduces sample viscosity
• C. Gel enhances clotting
• D. Gel acts as anticoagulant

Answer: (A)

The main idea is that the gel in serum separator tubes acts as a physical barrier after centrifugation, separating serum from the cellular components. Because the gel has a density between that of serum and the clot/cells, centrifugation moves it to the interface so a distinct gel layer forms between the serum on top and the clot and cells below. This barrier minimizes carryover of cells and cellular debris into the serum, reducing ongoing metabolism and protecting analyte stability during transport and storage. The gel is inert and does not participate in clotting or act as an anticoagulant, and it is not used to change viscosity or speed up clot formation.