Blood fractionation in the context of Plasma (blood)

Blood plasma is a light amber-colored liquid component of blood in which blood cells are absent, but which contains proteins and other constituents of whole blood in suspension. It makes up about 55% of the body's total blood volume. It is the intravascular part of extracellular fluid (all body fluid outside cells). It is mostly water (up to 95% by volume), and contains important dissolved proteins (6–8%; e.g., serum albumins, globulins, and fibrinogen), glucose, clotting factors, electrolytes (Na
, Ca
, Mg
, HCO₃, Cl
, etc.), hormones, carbon dioxide (plasma being the main medium for excretory product transportation), and oxygen. It plays a vital role in an intravascular osmotic effect that keeps electrolyte concentration balanced and protects the body from infection and other blood-related disorders.

Blood plasma can be separated from whole blood through blood fractionation, by adding an anticoagulant to a tube filled with blood, which is spun in a centrifuge until the blood cells fall to the bottom of the tube. The blood plasma is then poured or drawn off. For point-of-care testing applications, plasma can be extracted from whole blood via filtration or via agglutination to allow for rapid testing of specific biomarkers. Blood plasma has a density of approximately 1,025 kg/m (1.025 g/ml). Blood serum is blood plasma without clotting factors. Plasmapheresis is a medical therapy that involves blood plasma extraction, treatment, and reintegration.

A blood donation occurs when a person voluntarily has blood drawn and used for transfusions and/or made into blood products and biopharmaceutical medications by a process called fractionation (separation of whole blood components). A donation may be of whole blood, or of specific components directly (apheresis). Blood banks often participate in the collection process as well as the procedures that follow it.

In the developed world, most blood donors are unpaid volunteers who donate blood for a community supply. In some countries, established supplies are limited and donors usually give blood when family or friends need a transfusion (directed donation). Many donors donate for several reasons, such as a form of charity, general awareness regarding the demand for blood, increased confidence in oneself, helping a personal friend or relative, and social pressure. Despite the many reasons that people donate, not enough potential donors actively donate. However, this is reversed during disasters when blood donations increase, often creating an excess supply that will have to be later discarded. In countries that allow paid donation some people are paid, and in some cases there are incentives other than money such as paid time off from work. People can also have blood drawn for their own future use (autologous donation). Donating is relatively safe, but some donors have bruising where the needle is inserted or may feel faint.