What is Centrifugation?

Centrifugation is a method of separating molecules having different densities by spinning them in solution around an axis (in a centrifuge rotor) at high speed. It is one of the most useful and frequently employed techniques in the molecular biology laboratory. Centrifugation is used to collect cells, to precipitate DNA, to purify virus particles, and to distinguish subtle differences in the conformation of molecules.
It is commonly used in blood laboratories for separating the components of blood. After centrifugation, the component of blood separates into three distinct parts. From below upwards, the layers are – a layer of red blood cells (RBC), a layer of white blood cells(WBC) and platelets, and a layer of plasma at the top.

What is the need for centrifugation of Blood?
It is important to separate the cellular and liquid portions of a blood specimen as soon as possible when the test requires a sample of serum or plasma. This is because the cells interact with the serum/plasma, altering its chemical composition and affecting test results. Each part of the blood has a different function. Separating the blood into parts lets patients get only the specific part or parts of the blood that they need. So a whole blood donation can be used for several patients.