Go here for details on The Tenderfoot. How Anticoagulants Work Anticoagulants prevent the blood from clotting by removing the essential factors necessary for coagulation. The anticoagulants used in laboratories either precipitate calcium, bind calcium or inhibit thrombin. However, the oxalates causes crenation of the red blood cells and bizarre forms of lymphocytes and monocytes, making them unsatisfactory for routine hematology procedures. EDTA and SPS are chelating agents.
Chelation involves the bonding of metal to a molecule that has two more polar groups.
When this happens, a complex molecule is formed, removing the availability of calcium for the coagulation process. Potassium salt can also be used in preference of the sodium salt because of its greater solubility. EDTA is used perhaps more than any other anticoagulant for hematologic procedures. SPS, which is a weak chelating agent, is primarily used in the collection of blood cultures. Sodium citrate also binds calcium by forming a soluble complex.