The laboratory centrifuge is a central tool in many scientific protocols. Its ability to quickly separate the phases of a liquid sample makes it an essential piece of equipment in biology, biochemistry, medicine, and even the food industry. But what is the physical principle that makes it so efficient? And how does its design enable such precision? Let's dive into how this often-misunderstood device actually works.
The physical principle behind centrifugation
The laboratory centrifuge relies on a simple phenomenon: centrifugal force. By spinning a sample at high speed around a central axis, this force pushes the particles outward, depending on their density. Heavier elements are thus propelled to the bottom of the tube, while lighter components remain on the surface.
This force is proportional to the mass of the particles, the rotation speed and the distance between the particle and the rotation axis. It is this combination that allows for rapid, precise and reproducible separation, much more efficient than natural decantation.
The technical components of a laboratory centrifuge
To generate and control this force, the laboratory centrifuge is made up of several essential elements:
- The motor : located at the base, it allows the rotor to turn at speeds sometimes reaching up to 30,000 revolutions per minute in the case of high-end models.
- The rotor : This is the central part that holds the sample tubes. It can be fixed, angled, or pivoting depending on the sedimentation requirements.
- The centrifuge chamber : an isolated compartment that guarantees user safety in the event of imbalance.
- The control panel : this allows you to adjust the speed (in RPM or RCF), the time and sometimes the temperature if the centrifuge is refrigerated.
Rotational speed and relative centrifugal force (RCF)
We often talk about speed in revolutions per minute (RPM), but in reality, the more relevant measurement is the relative centrifugal force (RCF), expressed in "g." It takes into account both speed and rotor radius. Two centrifuges at the same speed can generate different centrifugal forces if their rotors are different sizes.
RCF = 1.12 × r × (RPM/1000) 2 , where r is the distance (in cm) between the axis of rotation and the bottom of the tube. This formula allows laboratory technicians to adapt their protocol from one machine to another.
Technology that adapts to sample types
The operation of the laboratory centrifuge can be adjusted according to the nature of the samples to be analyzed:
- For blood cells : a moderate speed is sufficient, otherwise the cell membranes will be damaged.
- For proteins or viruses : higher speeds are needed to precipitate finer particles.
- For solvents or organic phases : specific tubes, resistant to chemicals, and a configuration adapted to the density of the liquid will be used.
The centrifuge is therefore much more than a simple mechanical tool: it adapts to each protocol to guarantee a reliable and usable result.
Master the settings to avoid errors
Improper use can not only distort the results but also damage the device. It is therefore essential to master the following parameters:
- Balancing : The tubes must be positioned perfectly symmetrically. An imbalance can cause vibrations or even an emergency shutdown of the device.
- Rotor type : Some are designed for conical tubes, others for microplates. Choosing the right one is essential for consistent separation.
- Temperature : Some molecules are sensitive to the heat generated by rotation. In this case, a refrigerated centrifuge is essential.
Going further: maintenance and calibration
Proper operation also requires regular maintenance. A poorly maintained laboratory centrifuge can lose precision or become unstable. It is recommended to:
- Clean the rotor and chamber regularly with suitable products.
- Check the seals, brakes and opening system.
- Have the device checked once a year to ensure the accuracy of the speeds and forces applied.
And then?
Understanding how it works isn't enough: you also need to know how to apply it correctly on a daily basis. To find out how to use your juicer properly, read our complete user guide .
Common mistakes to avoid when using
Even with good equipment, improper use can compromise sample integrity or damage the laboratory centrifuge . Here are the most common mistakes, and how to avoid them:
- Uneven filling of the tubes: a difference in volume or density between the tubes causes an imbalance, a source of vibrations or mechanical degradation.
- Using incompatible tubes: Tubes must be resistant to the expected centrifugal force. Some plastics may deform or burst at high speeds.
- Overfilling: Always respect the maximum recommended level to avoid leaks or cross-contamination.
- Improper lid closure: A poorly locked lid prevents the appliance from starting or, worse, may open during the cycle.
Examples of concrete applications
The laboratory centrifuge is used in a wide variety of fields. Here are some examples of its operation applied to real-life contexts:
In medical biology
It is used to separate the components of blood. A tube containing whole blood centrifuged at approximately 3,000 g for 10 minutes produces three phases:
- Plasma (upper part, yellowish)
- The buffy coat (thin white layer of white blood cells and platelets)
- Red blood cells (dark red lower part)
In molecular biology
Microcentrifuges are used to precipitate DNA or proteins after extraction. The correct choice of centrifugation speed and duration is crucial to preserve the integrity of the genetic material.
In analytical chemistry
Centrifugation separates insoluble solids from a liquid phase, facilitating spectroscopic or chromatographic analyses. The sample often needs to be cooled to prevent the evaporation of volatile solvents.
The role of the rotor in performance
The rotor is the mechanical element that transmits centrifugal force to the samples. There are two main types:
- Fixed-angle rotor : The tubes are inclined at a constant angle (approximately 45°). This type allows for rapid separations, with sediment deposited on the lower wall of the tube.
- Free-rotor or swinging rotor : the tubes are positioned vertically at rest and tilt during rotation. They are recommended for smoother and more uniform separation, particularly in the case of density gradients.
Some laboratory centrifuge models allow different rotors to be interchanged, making the device more versatile.
Advanced features on modern models
Today's centrifuges incorporate useful features to improve reliability and safety:
- Cycle programming: duration, acceleration, deceleration, temperature.
- Automatic rotor recognition: to avoid overspeeding.
- Electronic lock: the machine will not start if the cover is not properly closed.
- Temperature control: crucial for sensitive substances such as enzymes or lipids.
- Soft braking: prevents sediment from re-suspending once rotation is complete.
Frequently asked questions about how it works
Can several different samples be centrifuged at the same time?
Yes, but only if the volumes and densities are the same or balanced. You must also ensure that you use tubes compatible with the same type of rotor.
Is centrifugal force always the same as speed?
No. Speed (RPM) is a raw data. Centrifugal force (RCF) is a more accurate measurement because it takes into account the rotor radius. For the same volume, two different centrifuges can produce very different centrifugal forces.
Why is my juicer vibrating?
Vibrations can be caused by tube imbalance, improper rotor timing, or overloading. Also check for cracked tubes or missing counterweights.
Why buy your juicer through Rewake?
Rewake is a specialist in refurbished laboratory equipment , carefully selected to guarantee performance equivalent to new, at a reduced price. Here are the concrete advantages:
- Tested and certified devices : Each laboratory centrifuge is rigorously inspected and calibrated.
- Prices up to 50% cheaper than equivalent new models, without compromising on reliability.
- Responsive after-sales service and personalized advice : the Rewake team helps you find the model suited to your field of activity.
- Eco-responsible approach : by extending the life of equipment, you reduce your environmental footprint.
Whether you are an academic, hospital or private laboratory, you will find a durable and economical solution among our available centrifuges.
