How Does a Centrifuge Work in a Lab?


A centrifuge separates particles from a solution and is a common piece of lab equipment. The particles are separated based on their size, shape, density, and viscosity. Depending on the rotor speed, the separation process takes place. 

Today, centrifuges are one of the most common pieces of laboratory equipment. Numerous labs use them, but perhaps chemistry, biochemistry, and molecular biology labs use them most often. They can be found in both clinical and research settings. 

Among their most common applications are separation, purification, and isolation of organelles, cells, and cell components, as well as nucleic acids, proteins, and viruses for further study.

Although centrifuges have a long history—they were first used to separate cream from milk since the late 1800s—they didn’t see much advancement in their capabilities (maximum centrifugal force) until advances in biochemistry led to a subsequent demand for devices with higher levels of centrifugal force.

As a result of these demands-the need to separate cell components, and later, a growing demand in virus research-a number of developments in centrifugation technology resulted, eventually leading to the commercial centrifuge that we all use today.

How Does A Centrifuge Work?

The centrifuge separates heterogeneous mixtures based on their densities – liquids in liquids, solids in liquids, and liquids in gases. A common use is to separate red blood cells and other blood components from whole blood. work on the sedimentation principle. Particles in suspension tend to settle out of the medium where they are entrapped and come to rest against a barrier during sedimentation. Centrifuges use centrifugal acceleration to separate particles from solutions.

Solution particles sink to the bottom of the tube if the density of the solution is higher than the density of the solvent. Particles float to the top of a solution if the density of the solution is lower than the density of the solvent. 

Particles move faster when the density difference between the solution and the solvent is greater. As long as the density between the two remains the same, the particles will remain stable in the solution. 

Centrifuges are used when there is little or no difference in density between the particles and the solution to be separated. Instead of relying on gravity to separate the particles, centrifuges create a centrifugal force.

The Workings Of A Centrifuge

Centrifuges spin liquid samples at high speeds using a motor. RCF, or relative centrifugal force, is the unit of measuring speed at which a centrifuge’s rotor moves. 

Many devices, however, display speed in RPM, or revolutions per minute. Solids settle completely and rapidly due to centrifugal force moving dense components to the outside of the container. 

centrifuges come in different sizes, capacities, and types of rotors. Centrifuge rotor types play a crucial role in your decision-making when it comes to acquiring a centrifuge for your laboratory. You can use a rotor for different types of applications, because the rotor affects the type of application.

Additionally, centrifuges use glass or plastic tubes that fit into the rotor cavities. Sample tubes of different sizes and types can be used in the unit depending on their size and type. 

The types and uses of centrifuges

Small Bench Centrifuges

Known as benchtop centrifuges, these collect small amounts of material such as yeast cells and erythrocytes. Gravitational force or g-force (g) is defined as 3,000 to 7,000 times the force of gravity for small bench centrifuges.

In comparison to other options, these have a relatively low speed. This is a general-purpose centrifuge that is among the most affordable on the market.

Large Capacity Refrigerated Centrifuges

Refrigerated centrifuges with large capacities have refrigerated rotor chambers. It’s possible to change the rotor chambers to accommodate a different size. With a maximum speed of 6,500 g, they collect substances that sediment rapidly, like small bench models.

High-Speed Refrigerated Centrifuges

High-speed centrifuges are similar to large capacity centrifuges, except they can reach speeds of up to 60,000 g. They can collect larger cellular organelles, cellular debris, microorganisms, and proteins precipitated by ammonium sulfate. Additionally, refrigerated models can have refrigerated rotor chambers.

Ultra Centrifuges

A high-speed ultra centrifuge can spin at speeds as high as 1,000,000 g (9,800 kilometers per second or 6,089 miles per second). There are two types of centrifuges: preparative and analytical.

Preparative Ultracentrifuges

In preparation ultracentrifuges, the weight reaches about 600,000 grams. Among other things, they can determine the shape and mass of macromolecules, separate lipoprotein molecules from plasma, and perform a variety of other tasks. During preparation, ultracentrifuge chambers are refrigerated, sealed, and evacuated.

Analytical Ultracentrifuges

light absorption, Schlieren, and Rayleigh interferometry. 

index of the solution, whereas light absorption systems detect changes through ultraviolet light absorption. Approximately 500,000 grams are required to run these models.

Centrifuge Rotors Types

It’s also important to consider the centrifuge rotor, since it determines what the machine can do and how much it costs.

Swinging Bucket Rotors

These rotors feature buckets that start in a vertical position and swing into a horizontal position during acceleration. The tube and its solution are aligned parallel to the centrifugal field and perpendicular to the axis of rotation.

Fixed Angle Rotors

Using this rotor design, the sample types are held at a constant fixed angle – between 14 and 40 degrees. As a result of the centrifugal force, the particles must move outward and collide with the centrifuge tube’s outer wall. 

Continuous-Flow Rotors

There is a higher concentration in this region, and it has a higher density than the surrounding medium. In the tube’s outermost point, the precipitate forms a compact pellet.

Continuous-flow rotors and drum rotors aren’t used as often as fixed angle or swinging bucket rotors for specialized applications. The importance of continuous flow becomes evident when it is needed.

As a time-saver, it allows for efficient separation of large volumes of material at high centrifugal forces without filling and decanting dozens of centrifuge tubes or frequently starting and stopping the rotor.

Cell and algae harvests, mitochondria, large viruses, bacteria, and tissue homogenates are all suitable applications for flow rotors.