Centrifuges: Functions and Laboratory Applications

Sorvall Legend Micro 17 and 21 Microcentrifuge Series

Image Courtesy of Thermo Scientific

A number of types of centrifuges are specialized in their uses. They are all used to spin biological samples to separate components within the specimen. Centrifugal forces cause the heavier materials to go to the bottom of the tubes. Samples are centrifuged at speeds that vary by procedure and type of sample. Most commonly, blood is separated for tests where the liquid portion (serum or plasma) is to be used in the procedure.

Specimens that require blood cells would not normally require centrifugation. The basic parts of the centrifuge, regardless of type, are similar. The rotor is the part that is spun by the motor of the centrifuge, and is controlled by a timer and a speed control. Centrifuges are differentiated by the jobs for which they were developed.

Common centrifuges used for separating blood into solid and liquid components whether as plasma (derived from anticoagulated specimens) or serum (obtained from clotted samples) are the most numerous types found in the laboratory, and most laboratories have at least several of each for basic types.. A microcentrifuge, or microfuge, is one that is used to spin small tubes at high speeds that may be as great as 14,000 rpm (revolutions per minute). Other models, called clinical centrifuges, operate in the range of up to roughly 3,000 rpm, and are used to concentrate sediment from urine samples and to separate serum or plasma from whole blood samples. One common specialized centrifuge used in blood banking, or immunohematology is the serofuge, for use in washing of red blood cells in small tubes of 2 to 3 mL. Other centrifuges may be required depending on types of specimens and procedures. Some require high-speed refrigerated centrifuges; some require various types of specimens and differing sizes of collection tubes and containers.