What is the substance called that is found inside a serum separator tube?

The substance found inside a serum separator tube is referred to as thixotropic gel. This gel is specifically designed to create a physical barrier between the serum and the cellular components of the blood after centrifugation. It helps to separate the serum from the cells, allowing for easier collection of serum for testing without the risk of contamination from cellular elements.

The thixotropic gel's properties allow it to remain in a liquid state during the centrifugation process and then solidify when the tube is settled, thus effectively forming a barrier. This feature is particularly beneficial in laboratory settings, as it helps maintain the integrity of the serum sample for various diagnostic tests.

Other substances mentioned, such as gelatinous matrix, sodium citrate, and silica, serve different purposes in blood collection and processing. Sodium citrate is an anticoagulant commonly used in tubes intended for coagulation testing, while silica is often found in certain types of tubes used for clot activation. However, in the context of a serum separator tube, thixotropic gel is the essential component for achieving serum separation.