Centrifuges: Continuum of Options and Features for High-use Devices
There are many ways to differentiate centrifuges by type, speed, and features.
Centrifuges are among a select group of laboratory instruments that are as scalable as they are configurable. Individuals who have used benchtop centrifuges that handle sub-milliliter volumes may be surprised to learn that centrifuges— some as large as rooms—are used in industrial processing.
Basic centrifuge designs are simple, consisting of an enclosed compartment inside which a rotor spins rapidly. Rotors, which can usually be interchanged, contain equally spaced openings into which sample tubes are inserted. Samples will either spin at a fixed angle relative to the rotating axis or “swing out” to perpendicular under centripetal force as the rotor speed increases. Forces generated as the rotor spins cause components in the sample to migrate toward the bottom of the sample tube, according to weight or density.
Entry-level mini-centrifuges easily fit on a benchtop, operate at a single, relatively low speed, generate low gravitational (g) forces, and cost only a few hundred dollars. “Minis” are used for samples whose components are easily separated by density. Most medical and veterinary office centrifuges are of this type. The next level up, compact benchtop centrifuges, spin tubes of up to about 2 mL and create tens of thousands of gs. Researchers use them to separate DNA, proteins, and cellular components.
Beckman-Coulter (Fullerton, Calif.), for example, divides its product line into three basic platforms: benchtop devices operating at up to about 10,000 rpm, “washing machine” centrifuges that provide up to about 100,000 g, and ultracentrifuges that deliver in excess of one million g. In fact, one could argue that all centrifuges exist along a continuum of features that may be mixed and matched, which include g-force generated, sample tube size, refrigeration capabilities, rotation angle, computerization, and others.
Michael Rosenblum, marketing VP at LabNet International (Edison, N.J.), offers the following considerations when purchasing a lab centrifuge:
- What size tubes do you expect to run?
- How fast does your sample need to spin to achieve the desired separation?
- Is an angled rotor or a swing-out rotor best for your application?
- Does your sample require refrigeration?
- What is the range of applications you are likely to encounter?
Angled vs. swing-out tube design affects speed and g-force, and provides sample collection options (spin-out is slower but provides a clean pellet). Refrigeration is desirable because samples heat up during a long run. It all comes down to your expected application range and the likelihood that the instrument you buy will be flexible enough to meet your needs.
Price was conspicuously absent from the list because lab centrifuges tend to be inexpensive compared with other high-use lab instruments. The price “sweet spot” of about $300 for unrefrigerated, single-speed mini-centrifuges up to about $6,000 for high-speed, refrigerated benchtop instruments covers most applications in the life sciences and other industries.
Computerized methods
Because their operation depends on applying physical forces to samples by spinning, centrifuges have not experiSeal buckets with a simple one-handed snap. It’s just one way Thermo Scientific centrifuges make your life easier because they’re designed for the way you work. With superior performance, reliability and rotor support built-in–it’s the little things that are no small matter when it comes to keeping you happy and productive:
- Innovative and certified ClickSeal® bucket sealing system: glovefriendly, one-handed snap-on covers replace screw caps and clips.
- Easy and secure AutoLock® rotor management: exchange rotors in less than 3 seconds with the push of a button, switching from high capacity to high performance.
- Thermo Scientific Fiberlite carbon fiber rotors: speed, versatility and corrosion-resistant design to maximize performance.
Getting the max out of your centrifuge shouldn’t take extra work . To learn more about Thermo Scientific general purpose centrifuges, visit www.thermo.com/centrifuge
