Choosing the Right Centrifuge for Your Application by Tammy Goodman

A centrifuge is a critical piece of 8. Do you have any space restrictions, equipment for the laboratory, and such as benchtop or floor space only? often a significant investment. 9. Do you have special needs such as Therefore, when the time comes to process traceability, user lock-out, add a new centrifuge—or replace an or biocontainment? old one—it is important to make an 10. What is your budget? informed decision. There is a good chance that your needs have changed Once you have answered these ques- since the last time you purchased a tions, you should have a better picture centrifuge. For example, space may of your centrifuge requirements. It is now be tighter, or the activity level also helpful to review the basic types of the laboratory may have increased of centrifuges to make sure you know substantially and there are now many which category best fits your needs. more users. Perhaps you want to try a new protocol that you learned about at a recent conference. Floor model or benchtop? With so many recent advances in both science and technology, it is wise to Centrifuges are generally classified educate yourself about the wide range as either floor-standing or benchtop of centrifuge options now available. models. Within each category are sev- eral platforms from which to choose. This will help you choose a model that Figure 1 Superspeed centrifuges are an The style you choose is typically deter- will suit your needs not only today, but excellent choice for multiuser, multiprotocol envi- mined by performance requirements, for many years to come. ronments, offering high capacity, high g-forces, available space, and budget. and a broad range of rotors and accessories. Following are some key questions that can be used to determine the type of cen- Floor-model centrifuges free up bench trifuge that will best meet your needs: space and are often chosen for either high-speed or high-capacity sample pro- models offer a choice of up to 40 rotors, 1. What applications and protocols will cessing. Within the floor-model category making them an excellent solution for the centrifuge be used to support? there are superspeed centrifuges, ultra- core laboratories performing general 2. What are the maximum and centrifuges, and low-speed centrifuges. preparative applications such as whole minimum g-force (relative cen- cell separations, protein precipitation, trifugal force, RCF) and volume Benchtop centrifuges offer versatil- tissue culture, subcellular isolation requirements? ity and convenience, and can be (i.e., Golgi bodies, ribosomes), plasmid 3. How many tubes or samples must equipped many ways to accommodate preps, and DNA/RNA separations. be processed in a run, shift, or day? a broad range of needs, making them a 4. What types of sample formats will cost-effective solution for many labo- Superspeed centrifuges are also the the centrifuge need to support ratories. Benchtop platforms include best option for multiuser, multipro- (i.e., microplates, blood collection general-purpose centrifuges, micro- tocol environments. Their versatility tubes, disposable conical tubes)? centrifuges, small clinical centrifuges, enables researchers to step into new, 5. What type of rotors will be needed cell washers, and high-speed models. cutting-edge technologies without to support your applications (i.e., purchasing a dedicated centrifuge for fixed angle, swinging bucket)? Choosing the right floor- one specific application. The maxi- 6. How many people will be using mum RCF on a typical superspeed the centrifuge? model centrifuge centrifuge is 70,450 × g, with a volume 7. Is versatility important? That is, range of 1.5 mL–1000 mL. do you anticipate the need for a Superspeed centrifuges broad range of protocols and mul- If you are looking for high capacity, tiple users, or will you be perform- high g-force, and versatility, a super- Ultracentrifuges ing the same standardized protocol speed centrifuge (Figure 1) is prob- If your application calls for g-forces of day after day? ably the best choice. Many superspeed up to 1,000,000 × g, you will need an

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also be equipped with specially prep kits. Designed to spin up to 2-mL designed rotors and liners for the volumes, microcentrifuges are typi- blood banking industry. cally equipped with rotors that accept commonly used 0.2-mL PCR tubes and 1.5-mL/2.0-mL disposable micro- Choosing the right centrifuge tubes and filters. benchtop centrifuge Whether you are looking for some- Clinical benchtop thing versatile that your laboratory centrifuges can grow into, or a dedicated cen- These compact models are designed Figure 2 General-purpose benchtop centri- trifuge for specific protocols, there is a benchtop centrifuge to meet for use in hospitals and clinics that fuges offer versatility and convenience, and can require a low-throughput unit to be equipped many ways to support tissue culture, those needs. Benchtop centrifuges are available in a wide variety of spin blood collection tubes and urine DNA/RNA research, cell harvesting, subcellular samples at very low speeds for diag- separations, and many other applications. platforms designed for different application requirements, includ- nostic examination. Most of these ing general-purpose benchtops, centrifuges spin at RCFs at or below ultracentrifuge. These extremely pow- microcentrifuges, small clinical cen- 3000 × g. The volume supported by a erful floor-model centrifuges support trifuges, cell washers, and high-speed typical clinical benchtop unit ranges sample volumes ranging from 0.23 benchtop centrifuges. from 3-mL up to 15-mL tubes, with mL to 250 mL. Within the ultracen- throughput ranging from 4 to 28 trifuge line there are two platforms: tubes per run, depending on the tube full-size floor models, which support General-purpose benchtop size and unit selected. g-forces of up to 802,000 × g and vol- centrifuges umes up to 250 mL; and microultra- Cell washers centrifuges, which support g-forces of These workhorse units (Figure 2) are the most common type of centrifuge These special-purpose centrifuges sup- above 1,000,000 × g and microvolume port very specific applications in the samples up to 13.5 mL. found in the laboratory. Their versa- tility makes them extremely practi- clinical and medical industry: wash- cal: They offer a wide range of rotor ing away cellular debris, extraneous Common ultracentrifuge applications proteins, and other constituents of include the separation of virus parti- types, volumes, and speeds within a single unit to meet the demands of donor blood from red blood cells. The cles; DNA, protein, or RNA fraction- washed red blood cells are used for ation; as well as lipoprotein flotation. many common protocols. General- purpose centrifuges are typically tests such as cross-matching prior to Density and size gradient separations blood transfusion. Cell washers spin at are also regularly performed in ultra- used for tissue culture, DNA/RNA research, cell harvesting, subcellular RCFs at or below 1500 × g and support centrifuges and, more recently, a num- 3-mL and 5-mL culture tubes. ber of new nanotechnology applica- separations, protein work, and many tions have appeared. other applications. Some general- purpose benchtops offer RCFs of up High-speed benchtop to 24,000 × g; typical volume ranges Low-speed centrifuges are 0.2 mL–750 mL. Most general- centrifuges These large-capacity centrifuges have purpose units can be equipped with a These powerful and compact units fairly specific applications due to the broad range of swinging-bucket and offer g-forces close to that of a floor- maximum RCF of approximately 7000 fixed-angle rotors, making them an model superspeed centrifuge, but with × g (note: the maximum g-force varies excellent fit in a multiuser envi- slightly depending on rotor and unit). ronment where floor space is an The most common low-speed applica- issue and RCFs of up to 24,000 × tion is the separation of whole cells, g are sufficient. for example, separating red blood cells and platelets from whole blood. The second most common application is Microcentrifuges the whole cell harvest step in the pro- Like the general-purpose benchtop cessing of large volumes of cultures models, microcentrifuges (Figure from bioreactors in the bioprocessing 3) are a necessity in every labo- and pharmaceutical industries. ratory. These compact units pro- vide RCFs of up to approximately Low-speed centrifuges offer a basic set 21,000 × g, which is sufficient Figure 3 Microcentrifuges are a necessity in of rotors that support volumes ranging for the most common microvol- every laboratory for everyday microvolume applica- from 1.5 mL (with the use of adapt- ume applications such as plasmid, tions such as plasmid, DNA and RNA work, and ers) up to 2000 mL. These units can DNA and RNA work, and mini- miniprep kits.

X NOVEMBER/DECEMBER 2007 • AMERICAN LABORATORY AMERICAN LABORATORY • NOVEMBER/DECEMBER 2007 X CHOOSING THE RIGHT CENTRIFUGE continued a limited set of rotors. The most com- A long-term investment application needs and doing some mon rotors and applications for this up-front research will optimize your type of centrifuge include a low-speed, Understanding the different types of centrifuge purchase and ensure that it high-volume swing-out rotor for a centrifuge platforms and the applica- provides a long-term investment that whole cell harvest step; a high-speed, tions they support is a good first step in will support your research for many midvolume (i.e., 50–15 mL) fixed- the selection process. Once you have years to come. angle rotor for a subcellular pellet- identified your application needs and ing step; or a high-speed, low-volume the appropriate centrifuge model, your (1.5-mL/2.0-mL) fixed-angle rotor for centrifuge supplier should be able to certain DNA/RNA applications. The assist you in configuring the best system Ms. Goodman is Sample Preparation and average maximum RCF for a high- (centrifuge, rotor, and consumables) to Separations Applications Product Man- speed benchtop is 50,000 × g, with a meet your specific requirements. ager, Thermo Fisher Scientific Inc., volume range from 1.5 mL to 200 mL 275 Aiken Rd., Asheville, NC 28804, over a range of swinging-bucket and Performing a thorough assessment U.S.A.; tel.: 828-365-1348; e-mail: fixed-angle rotors. of your current and future centrifuge [email protected].

X NOVEMBER/DECEMBER 2007 • AMERICAN LABORATORY AMERICAN LABORATORY • NOVEMBER/DECEMBER 2007 X