How a Centrifuge Works

Why wait hours for gravity when you can get results in minutes? A centrifuge accelerates natural separation processes, making it indispensable in modern laboratories. Here’s everything you need to know about how centrifuge machines work.

Drucker Diagnostics is a world leader in manufacturing centrifuges, and we have more units working around the globe than any other company. In this centrifuge machine guide, we will explain how a centrifuge works, from safe operation to common applications and more.

What Is a Centrifuge?

A centrifuge is a machine that uses centrifugal force to separate the contents of a sample based on their density. When the centrifuge spins, it creates a strong centrifugal force. Though separation would eventually happen naturally with Earth’s gravity, the centrifuge machine delivers rapid results for laboratory and other applications.

There are many types of centrifuges, varying by intended use and rotor design. Centrifuge types include:

• Benchtop centrifuge
• Microcentrifuge
• Floor-standing
• Large capacity
• STAT
• Refrigerated
• High speed
• Ultracentrifuge

What is Centrifugation?

Centrifugation is the process of concentrating the natural forces that act on all particles of different densities to accelerate the natural process of separation. It is what separates the particles by density in the test tube. Centrifugation can occur with either filtration or sedimentation methods. Filtration uses a mesh screen to hold back the solid components and allow the liquid components to flow through. Filtering does not work to centrifuge blood samples because the blood components are too small.

In either method, the particles are suspended in liquid and separated in the centrifuge machine. The separation happens due to centrifugal force, which pushes objects outward – toward the tip of the tube, in the case of blood tubes – as they are spun around in a circle.

Principles of Centrifugation

At its core, centrifugation is separation through sedimentation. The denser particles sink to the bottom of the container, while the more lightweight particles remain suspended. Centrifugation will displace particles that are even slightly different in density, and is influenced by these four factors:

• The density of the samples and solution
• The temperature and viscosity
• The distance that the particles are displaced
• The speed of rotation

Relative centrifugal force (RCF), or G-force, is the amount of acceleration that is applied to the sample. When RCF exceeds the buoyant and frictional forces in the sample, the particles will move away from the axis of rotation and result in sedimentation.

What Is a Centrifuge Used For?

Because centrifuge machines are excellent at separating particles by density, they are often found in laboratory settings where it is necessary to isolate certain biological components for testing. In a blood sample, for instance, there are red blood cells and plasma mixed together. After centrifugation, the red blood cells will be at the bottom of the tube and the plasma will be on top.

Centrifuging is necessary for research on particular components, such as separating out blood plasma for testing, isolating DNA, and even separating out urine sediment.

How Does a Centrifuge Work?

The purpose of the centrifuge machine is to replicate and accelerate centrifuging to separate components in a sample. Because of the forces involved, these machines are carefully designed to work efficiently while keeping the operator safe.

The Parts of the Centrifuge Machine

At the center of the centrifuge is a powerful motor that creates the spin. Attached to this motor is the rotor, in which will rest the containers that hold the tubes containing the material to be centrifuged. These containers may be spun at a 45-degree angle (fixed angle centrifuge), a 90-degree angle (horizontal centrifuge) or no angle (vertical centrifuge). Depending on the centrifuge, the tubes may either be loaded at the angle on which they will rotate (fixed angle is a good example of this) or be loaded into a container that will adjust itself to a different angle upon startup. This second methodology is referred to as swing bucket and is a common functionality in horizontal centrifuges.

Depending on the centrifuge selected, a variety of different controls may be available. Some centrifuges are pre-programmed for one, two, or three processing settings. Some are completely custom programmable with a digital display. Regardless of the control type, when you start the centrifuge, it will run the motor based on the settings provided. During the cycle, the sample in the test tubes will separate into their various components so they are ready for analysis.

How to Use a Centrifuge Machine

Despite the complex principles at work in the centrifuge, operating the machine itself is quite simple. To use a centrifuge machine:

1. Insert the test tube sample into one of the portals
2. If needed based on the number of samples you are testing, insert test tubes filled with water for balance
3. Secure the lid and select desired settings
4. Start the centrifuge and wait for it to complete the cycle
5. When the centrifuge has stopped spinning, take out the balances and samples
6. Each sample will now be separated into its various components and ready for analysis

Knowing how a centrifuge machine works is key to using it properly.

Balancing the Centrifuge Machine

When using a centrifuge machine, it is necessary to balance your samples. Balance the centrifuge machine by:

• Making sure all tubes are evenly filled with liquids similar in density
• Ensuring that the masses of the tubes are within 0.1 grams of each other
• Placing tubes opposite from one another inside the machine to keep the gravity in the center

When you test an odd number of tubes, it may not be possible to create balance. In these cases, fill another test tube with water and balance based on density and mass.

Care and Maintenance for the Centrifuge Machine

Ensure your centrifuge receives the proper care and maintenance so it provides reliable results, is safe to use and works for a long time. Regularly perform these checks:

• Education: Make sure that everyone who uses the centrifuge machine knows how to use it. Teach all laboratory staff how to balance samples, set speeds and take safety measures.
• Inspection: An inspection will alert you to any problems with the centrifuge machine. Look at the components for scratches or effects of chemical exposure. All are signs of wear and should be fixed as soon as possible.
• Awareness: When using the centrifuge, be aware of signs that something is wrong. If the machine is shaking, vibrating or grinding, stop it immediately.

Cleaning and disinfection are key to ensuring good centrifuge functionality in the long term. Using a neutral cleaning solution (like an alcohol-based disinfectant) and a soft cloth, wipe the:

• Rotors
• Rotor chamber
• Accessories
• Interior area
• Keypads
• Touch screens

Shop Drucker Diagnostics Centrifuge Machines Today

Does your laboratory need reliable, high-quality testing equipment? As the industry’s leading supplier and manufacturer of centrifuge machines and more, Drucker Diagnostics is here to keep your lab running. Shop our products and accessories today, and feel free to contact us with any questions.