Centrifuges play a pivotal role in multiple scientific industries with widespread applications. This equipment comes in a variety of different speeds, gravitational force and rotor types, each developed to help with a specific solution while working on the same sedimentation principle.
Centrifuges Defined
A centrifuge is a machine used in laboratories to separate liquids, gases and, occasionally, solids. Mixtures are placed in the spinning chamber, which rotates rapidly when turned on, causing the contents to move toward the outer edges of the chamber based on their density or size. Because they are useful in a wide variety of applications, centrifuges are commonplace in many different types of labs.
- Clinical lab: A lab technician may use a centrifuge to separate a patient's blood sample into red blood cells and plasma.
- Environmental lab: Centrifuges are used to separate and analyze samples of soil and water to help detect contaminants.
- Oil industry: Crude oil can be separated into various components with the help of centrifuges.
- Industrial lab: In the pharmaceutical, food and chemical industries, centrifuges play a role in separating different phases of a mixture.
What Does a Centrifuge Do?
The foundational concept of centrifugal technology is sedimentation, which states that a solution comprised of different base substances will separate when gravitational force is exerted upon them. Centrifuges utilize this phenomenon by spinning samples at a very high speed, measured as revolutions per minute (RPM). The resulting centripetal force causes the substances to move outward, where they naturally stack from least dense to most dense. The densest portion moves to the bottom of the stack and the least dense gathers at the top.
One spins samples by dispensing the fluid into test tubes, then loading the tubes into a rotor. The rotor is placed on the centrifuge’s spindle. After closing the chamber, the technician sets parameters on the centrifuge’s control panel and initiates the run. The run's parameters, such as duration, temperature and speed, are determined by a user’s application and the sample in question.
Should the application demand it, a technician can spin samples in microplates rather than test tubes. While this can increase sample throughput, it will require a microplate-compatible rotor.
Types of Centrifuges
Centrifuges come in different sizes and volume capacities depending on their application requirements. With each size comes different processing capacities. Centrifuges are typically classified as benchtop or floor units. Floor centrifuges have bigger chambers compared to other types of units. Therefore, they can fit some of the largest rotors and process more samples per run. On the other hand, benchtop centrifuges are compact, relatively portable and don't take up any floor space.
These equipment can be divided into the following types:
- Ultracentrifuge: These are the most powerful and high-speed centrifuges used in advanced research. Ultracentrifuges are often used for tasks like separating subcellular components and studying molecular structures, such as DNA and organelles.
- Microcentrifuge: These smaller and more compact versions of benchtop systems are commonly found in laboratories. Microcentrifuges are ideal for applications in which sample volumes are limited and bench space is tight. They're commonly used in hematology and microfiltration.
- Refrigerated centrifuge: If you need to preserve samples at a consistent temperature while they function at high speeds, refrigerated centrifuges are your best option. They're perfect for analyzing DNA, RNA and antibodies. These refrigeration systems use expansive chambers that are not easily compressed into small forms. That's why virtually all floor models are refrigerated while benchtop units only offer flexibility of space.
Centrifuge Features to Consider
When you're in the market for a centrifuge, there are various features to consider in addition to its size and capacity, including gravitational force and rotor types. Every feature comes with unique pros and cons that you should prioritize according to what you need it for.
Gravitational Force
The relative centrifugal force (RCF) is one of the fundamental concepts of centrifugation. RCF is the measurement of gravitational force applied to samples as they spin in the centrifuge. RCF is a value that can be calculated based on a rotor's RPM and its diameter. Just as each size of centrifuge is suited for different usage scenarios, each speed range is suited for unique applications as well.
The finer a component’s particles are, the stronger the centripetal force must be to adequately separate them. Thus, as granularity increases, RCF must increase as well. Because centrifugal force is a product of speed, one boosts RCF by increasing the centrifuge’s current RPM.
Since the typical speeds found in centrifuges have such a broad range, it's divided into the following three categories:
- Low-speed centrifuges operate at a maximum speed of up to 5,000 RPM.
- High-speed centrifuges usually work at a range between 15,000 and 30,000 RPM.
- Ultracentrifuges can reach speeds as high as 150,000 RPM.
Rotors
Another feature that affects the centrifugal process is having the right rotor type suitable for different applications. There are three main types of rotors:
- Fixed-angle rotors: These are the most common type of rotor and consist of a series of tube cavities lining the rotor's diameter, angled toward its center. They are frequently used to strain target particles, or "pellets," from samples while allowing you to discard the rest.
- Swing-bucket rotors: Also known as "swing-out" rotors, this type is the most ubiquitous type besides fixed-angle. They're designed to hold buckets — typically four of them — on trunnion pins, which allow them to swing freely as they spin. The centripetal force holds the buckets at a 90-degree angle for the duration of the run, which allows the sample to maintain its orientation before, during and after processing. Swing-bucket rotors require adapters to hold tubes, which are available in a variety of configurations and can have layers added or removed to accommodate vials of varying heights.
- Vertical rotors: As the name implies, vertical rotors hold sample tubes upright for the entire duration of the run. Considerably less common than fixed-angle and swing-bucket rotors, vertical rotors are used when the sample in question can pellet after moving only a very short distance.
Explore Used Centrifuges at New Life Scientific
A centrifuge is one of the most useful and valuable equipment for your lab. New Life Scientific provides high-performance centrifuges that are budget-friendly, with a 90-day warranty and customer support after your purchase.
Browse our selection of quality and cost-efficient refurbished centrifuges and accessories for your research and production needs. Not sure whether to choose a benchtop or floor centrifuge for your lab or organization? Get in touch with our team and we will help you find an option that will fit your needs!
