Centrifuge Device, Types, and Centrifugation

What is a Centrifuge?

A centrifuge is fundamentally a separation method. Using the centrifugal force generated by rotational motion, particles in a sample are separated according to their shape, size, and density. The history of the centrifuge dates back to the 18th century.

In a laboratory centrifuge that uses sample tubes, radial acceleration causes denser particles to settle at the bottom of the tube, while less dense substances rise to the top.

Centrifuge Device

Very high-speed centrifuges and ultracentrifuges that can achieve extremely high accelerations can separate fine particles down to the nanoscale and even molecules of different masses. Large centrifuges are used to simulate high-gravity or acceleration environments. Example: High-G training for test pilots.

Gas centrifuges are used for isotope separation, such as enriching nuclear fuel for fissile isotopes.

Centrifuge Tube

Centrifuge tubes are conical or cylindrical tubes made of pressure-resistant glass or plastic, into which the material to be centrifuged is placed. The type of sample and the sample volume influence the choice of tube.

What is Centrifugation and How is it Done?

First, the substance to be separated is placed in centrifuge tubes. These tubes are specially designed to fit centrifuge devices.
The tubes are placed into the centrifuge. Care must be taken to place the tubes symmetrically to ensure proper centrifugal force.
The speed of the centrifuge (revolutions per minute) is set, and the process is started.

Types of Centrifuges

There are many types of centrifuges, which can be classified by purpose of use or rotor design.

Types of Centrifuges by Rotor Design

Fixed-angle centrifuges are designed to hold sample containers at a fixed angle relative to the central axis.
Swing-bucket centrifuges, unlike fixed-angle ones, have a hinge that allows the sample containers to swing outward during rotation.
Continuous tubular centrifuges do not use separate sample containers and are employed for high-volume applications.

For What Purposes Are Centrifuges Used in the Laboratory?

A wide variety of laboratory-scale centrifuges are used in chemistry, biology, biochemistry, and clinical medicine to isolate and separate suspensions and immiscible liquids. They vary greatly in speed, capacity, temperature control, and other features.

Laboratory centrifuges are usually used with a variety of fixed-angle and swing rotors that can carry different numbers of tubes and are rated for specific maximum speeds.

Controls range from simple electrical timers to programmable models that regulate acceleration and deceleration rates, operating speeds, and temperature regimes. Another application in laboratories is blood separation. Blood is separated into cells, proteins, and serum. Another common application is DNA preparation, pharmacogenetics, and clinical diagnostics.