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Pharmaceutical, biopharmaceutical, and biotechnology companies, as well as hospitals, blood banks, diagnostics labs, and even food & beverage companies, have significant use for centrifugation of samples performed using a centrifuge. Simply put, a centrifuge is a machine with a rapidly rotating container that applies centrifugal force to its contents.
It is an indispensable piece of equipment because it can separate mixtures with relative densities, insoluble particles, immiscible liquids, sediment suspended solids, and blood. It can even simulate different types of gravity for astronaut training.
Centrifuges operate by placing an object in rotation around a fixed axis and applying an accelerative force perpendicular to the spin axis. The amount of accelerative force applied to a sample in a centrifuge is defined as the relative centrifugal force (RCF), or g-force. RCF is measured as multiple’s of Earth’s gravitational field (g).
There are three main types of centrifuges designed for various applications:
While centrifuges are considered a ubiquitous piece of laboratory equipment, you may still have questions about which model will fit your needs best. There are important considerations to make, and they mostly involve centrifugation speed, configuration flexibility, available lab space, and ease of use.
Read on to learn more about these considerations and the types of centrifugation and centrifuges most commonly used in clinical and research laboratories.
There are multiple types of centrifuges and centrifugation. While centrifugation is classified by application fit, centrifuges can also be classified by the intended use or rotor design.
What is centrifugation? In short, it’s the act of separating particles from a solution according to their size, shape, density, and medium viscosity using centrifugal force at various speeds and applying that force at different angles.
There are different types of centrifugation, with the two main types being differential centrifugation and density gradient centrifugation. Furthermore, density gradient centrifugation can be divided further: isopycnic and rate-zonal centrifugation.
This type is considered the simplest form of separation by centrifugation. It’s used to separate certain organelles from whole cells to further analyze specific parts of cells by applying different centrifugation cycles. These cycles facilitate faster sedimentation rates that naturally occur to particles of different densities or sizes in a suspension. In other words, by subjecting the suspension to increasing levels of force, particles of specific sizes will sediment at different rates more quickly.
Density gradient centrifugation:
On the other hand, this type is used to separate particles based on density as they pass through a density gradient while being subjected to centrifugal force. It is based on the principle that molecules settle once they reach a medium with the same density as their own. Using a medium with a density gradient that either decreases or increases, particles will separate at different layers as centrifugal force is applied.
The two types of density gradient centrifugation, isopycnic and rate-zonal, differ in that the rate-zonal method is used to separate particles that vary in size but not in density. In contrast, the isopycnic method separates particles that differ in density but not size.
There are at least three types of centrifuge rotors. These include fixed-angle rotors, swinging head (or swinging bucket) rotors, and vertical rotors. Centrifuge models can be classified based on the rotor design.
Fixed-angle rotor centrifuges are designed to hold the sample containers at a constant angle relative to the central axis. The angle the rotor holds the containers is typically 45°, which causes sedimentation to form on the side of the tubes. It can potentially be problematic if the solids get caught at the angle of the tube.
Swinging head (or swinging bucket) centrifuges, in contrast to fixed-angle centrifuges, have a hinge where the sample containers are attached to the central rotor. This allows all of the samples to swing outwards as the centrifuge spins.
Lastly, vertical rotor centrifuges differ from fixed-angle or swinging bucket rotors in that these types hold the sample containers in an upright position. Because the particles in suspension only have a short distance to separate, the run time is reduced, and the resolution is increased. A vertical rotor is commonly used for isopycnic and other density gradient separations.
A centrifuge’s intended use varies on its usability and purpose:
Many laboratory-scale centrifuges are used in chemistry, biology, biochemistry, and clinical medicine to isolate and separate suspensions and immiscible liquids. They vary widely in speed, capacity, temperature control, and other characteristics.
Specifically, laboratory centrifuges employ different fixed-angle and swinging bucket rotors, each of which can carry various amounts of centrifuge tubes while being rated for specific maximum speeds. Controls vary from simple electrical timers to programmable models that control acceleration and deceleration rates, running speeds, and temperature regimes.
Ultracentrifuges spin the rotors under vacuum, eliminating air resistance and enabling precise temperature control. Zonal rotors and continuous flow systems are capable of handling bulk and larger sample volumes, respectively, in a laboratory-scale instrument.
Here are a variety of lab-grade centrifuges available, many of which have specific benefits the end-user can take advantage of.
For example, microcentrifuges, devices for small tubes from 0.2 ml to 2.0 ml (microtubes), come equipped with 96 well-plates and offer a compact design with a small footprint. Clinical centrifuges are moderate-speed devices used for clinical applications like blood collection tubes.
Multipurpose high-speed centrifuges are devices used for a broad range of tube sizes and provide high variability; however, they typically have a large footprint.
Ultracentrifuges, which are analytical and preparative models, are used in cell and molecular biology and biochemistry to separate tiny particles in solution. This includes viruses, viral particles, plasmid DNA, RNA, proteins, and lipoproteins.
Because of the heat generated by air friction (even in ultracentrifuges, where the rotor operates in a good vacuum), and the frequent necessity of maintaining samples at a given temperature, many types of laboratory centrifuges are refrigerated and temperature controlled.
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Leases range from 2 to 5 years. Length will depend on several factors, including how long you want to use the equipment, equipment type, and your company’s financial position. These are standard factors leasing companies consider and help us tailor a lease agreement to fit your needs.
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Bundle preventive maintenance and repair coverage with your lease agreement. You can spread those payments over time. Easily maintain your equipment, minimize the chances something will break down, repair instrumentation quickly, and simplify your payment processes.
At the end of your lease, you have multiple options. You can either renew the lease at a significantly lower price, purchase the machine outright based on the fair market value of the original pricing, or call it a day and we’ll come the pick up the equipment for you free of charge.
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