Laboratory centrifuges use centrifugal forces to separate components of a fluid based on their densities. In a laboratory setting, samples are typically contained within a tube that is placed into the centrifuge rotor before being spun to separate its components. Rotor design can vary from centrifuge to centrifuge with fixed-angle and swing out rotors being the most common found in laboratories.
Centrifuges can vary greatly in their design and capacity ranging from microcentrifuges and minicentrifuges all the way to ultracentrifuges for large samples or industrial centrifugation. Aside from capacity, the most important specifications to consider when comparing centrifuges is their speed range and relative centrifugal force (RCF).
A centrifuges speed range, typically expressed in RPM, is a measure of how fast the centrifuge rotor is spinning. Typically, laboratory centrifuges allow the operator to control the speed of the centrifuge by adjusting the RPM. Microcentrifuges, the type of centrifuge used by most labs, are typically able to spin up to 15,000 RPM.
The relative centrifugal force, or RCF, is a measure of the forces applied to a sample and is expressed relative to earths gravitation force. The formula to calculate the RCF of a centrifuge is RCF = (RPM)2 × 1.118 × 10-5 × r.
Laboratory Centrifuges
By spinning at high speed, a centrifuge uses g-force to separate particulates in suspension according to their density. A laboratory centrifuge may be used for sedimentation of cells and viruses or to isolate macromolecules such as DNA. Application areas for centrifuges include biology, biochemistry, environmental, pharmaceutical, and clinical testing.
What Are Different Types of Centrifuges?
General-purpose benchtop or tabletop centrifuges are the most common type, with volume ranges covering 0.2 to 750 mL or so. Refrigerated units, compact mini centrifuges, and high-speed tabletop units with RCFs close to that of floorstanding models are also available. The g-forces of ultracentrifuges, often used in nanotechnology, can top 1,000,000 × g. Micro-centrifuges are for work with smaller micro-centrifuge tubes and PCR tubes.
What to Consider When Choosing a Centrifuge:
RCF is the most important indication of separation power.
Rotor types include swinging bucket, fixed-angle, or vertical, in plastic and metal versions.
Sample volume and available lab space are also important in determining the size of centrifuge needed.
Micro Centrifuges
Laboratory centrifuges spin a sample at high speeds in order to separate particles in suspension. Centrifuges are found in many types of labs including biological, environmental, pharmaceutical, and clinical labs. Microcentrifgues differ from standard laboratory centrifuges in the size of the tubes used. Microcentrifuge tubes are much smaller than standard tubes, generally in the 1.5-mL to 2-mL range, though models that support larger or smaller tubes can be purchased. When purchasing a microcentrifuge, it is important to consider temperature range, equipment size, speed, and size of centrifuge tubes accepted.
Refrigerated Centrifuges
Refrigeration constitutes an important added feature to any laboratory centrifuge. Refrigerated laboratory centrifuges temperature ranges as wide as -20C – 40C, making them perfect for DNA, RNA, PCR or antibody analysis. A refrigerated laboratory centrifuge can obtain rotational speeds of over 30,000 rpm, and a relative centrifugal force (RCF) of over 65,000 x g. A refrigerated lab centrifuge comes in a number of configurations, including swing bucket or fixed-angle types, or both. These centrifugation systems utilize centrifuge tips and tubes or well-plates for use in a number of applications, with capacities reaching 4 x 500 ml. It is important to seek refrigerated laboratory centrifuges with efficient cooling systems, automatic unit conversion capability, and other high-throughput enabling features.
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