Since blood coagulates naturally after blood collection in the past, it takes a long time for blood to be placed from centrifugation to measurement, which affects the full use of various functions of the analyzer. In order to rapidly advance the rapid detection technology, the addition of separating glue and coagulant to the blood collection tube shortens the blood clotting time. The application of separating gel to promote coagulation blood collection tube is an important quality control in the initial stage of blood collection, and it also prepares high-quality serum samples. From the perspective of protecting the indoor and outdoor environment, the application of serum separation gel blood collection tubes reduces the amount of serum cups and plastic test tubes.
Serum separation gel is composed of hydrophobic organic compounds and silica powder. It is a thixotropic mucus colloid. Its structure contains a large number of hydrogen bonds. Due to the association of hydrogen bonds, a network structure is formed. Under the action of centrifugal force, the network structure is It becomes a low-viscosity fluid when it is destroyed, and then re-forms a network structure after the centrifugal force disappears. This property is called thizotropy. That is, when the temperature does not change, a certain mechanical force is applied to this mucus colloid, which can change from a high-viscosity gel state to a low-viscosity sol state. If the mechanical force disappears, it will return to the original high-viscosity gel state. The interconversion between gel and sol produced by mechanical force was first named by Freundlich and Petrifi. Why does the interaction of gel and sol occur due to the action of mechanical force?
The thixotropy is because the structure of the separation gel contains a large amount of hydrogen bond network structure. At room temperature, hydrogen bonds are more likely to be severed and cause recombination. Silica has silicic hydroxyl groups (SiOH) on the surface to form SiO molecular aggregates (primary particles). The primary particles are linked by hydrogen bonds to form chain-like bonded particles. The chain-like silica particles and the particles of the hydrophobic organic compound constituting the separation gel further form hydrogen bonds to generate a network structure, forming gel-like molecules with thixotropy.
The specific gravity of the separation gel is maintained at 1.05, the specific gravity of the serum is about 1.02, and the specific gravity of the blood clot is about 1.08. When the separation gel and the coagulated blood are centrifuged in the same tube, the hydrogen bond network structure in the silica aggregate is caused by the centrifugal force applied to the separation gel. When it is destroyed and becomes a chain structure, the separation gel becomes a substance with low viscosity. The blood clot heavier than the separation gel moves to the bottom of the tube, and the separation gel reverses to form three layers of blood clot/separation gel/serum at the bottom of the tube. When the centrifuge stops rotating and loses the centrifugal force, the chain-like particles of the silica aggregates in the separation gel are again formed by hydrogen bonds to form a network structure, which restores the initial high-viscosity gel state, forming an isolation layer between the serum and blood clots.
In addition, laboratory medicine laboratories have widely used disposable hydrophobic plastic test tubes to extend the clotting time. When the plastic test tube is in contact with the coagulation factors Ⅺ and Ⅻ, the ability to be activated is very weak. The blood has not completely coagulated 2 to 4 hours after blood collection. For this reason, a coagulant is sprayed on the inner wall of the plastic test tube to accelerate blood coagulation, and high-quality Serum specimens.
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