Plasma is freed from the cells by the centrifugation. Clotting of blood is prevented by the addition of an anticoagulant directly after the taking of blood.

The lithium or sodium heparin is used as an anticoagulant.

Heparin is a natural anticoagulant which presents in any healthy body.

Powdered heparin is applied to the inner layer of the test tube. Immediately after taking the blood into the tube with heparin, it must be carefully mixed at least 8-10 times.

Test tubes with sodium heparin are used when it is necessary to determine the level of lithium in the patient’s blood, which is relevant in psychiatric practice.

	Usage: electrolyte analysis, clinical chemistry, haematology.		Specimen: heparin plasma.
	Clotting time (after insertion into the tube): 30 minutes.		Conditions of centrifugation: 2000 – 3000 g for 15 min. Centrifugation should be made right after the drawing the blood into the tubes.