Laboratory Centrifuges are used in a variety of applications to separate components in samples. This is achieved by spinning the samples at high speeds and at different temperatures. Centrifuges are available in different sizes with different max speeds, rotors and different temperature options.
View of the inside of a laboratory centrifuge, showing a fixed angle rotor
Centrifuge FAQ:
Do I require a Refrigerated Centrifuge?
Refrigerated centrifuges are used when samples need a consistent temperature range whilst running at maximum speeds. The cooling function is within the chamber itself which works best for heat-sensitive samples, and helps overcome the heat generated by the friction of the motor. Refrigerated centrifuges can also have heating abilities allowing it to maintain a higher than ambient chamber temperature.
What size/make of centrifuge is better for my area of study?
Mini centrifuge - Low speed laboratory centrifuges that are ideal when processing a small number of tubes, and will use the same method every time. Has a small capacity and will accept tubes around 0.5-2.0ml
Micro centrifuge - High speed laboratory centrifuges that are best for micro-samples and clinical applications. Mainly used for biological separations of RNA, DNA, peptides, and cellular materials. Some models can accept blood or urine samples. Has a medium capacity that will accept tubes around 5ml
Multi purpose centrifuge - Models can be refrigerated or non-refrigerated. Has a large capacity and is used for high throughput applications or for methods involving larger tubes and sample volumes. Can accept tubes up to 750ml
Mini centrifuge
Micro centrifuge
Multi purpose centrifuge
What is the difference between IVD and GLP?
IVD Regulation 98/79/EC provides clarity on which products can be classed as in-vitro diagnostic (IVD) devices that are predominantly used if your lab work is a medical, clinical or diagnostic application. This regulation is being replaced by the EU IVD Regulation 2017/749 in May 2022. IVD compliant products have a number of additional pieces of documentation and analysis to meet the regulation requirements such as:
- Risk analysis procedures
- interaction with authorities
- Market surveillance
- Additional labeling requirements
If your laboratory work is mainly researched based then a General Lab Product (GLP) should be used.
Do I need an adapter?
Adapters are useful if you need to use different tubes in one bucket, allowing several experiments to occur at the same time or different sample volumes. Ideally the adapter should come from the same manufacturer as the centrifuge and rotor as the adapter has been made and tested against these. Some useful tips for picking the right adapter, the adapter should:
- cover 2/3 of the tubes length but should not exceed the tubes length
- be shaped to fit the tubes bottom - conical, round-bottom, flat-bottomed etc
- support the walls of the tube but should not squeeze it
- not prevent the centrifuge from reaching the required g-force
What is the difference between RCF and RPM?
RPM - rotation per minute, tells you how many times the rotor will spin per minute. The RPM cannot be compared across different centrifuges as the force being exerted is not specified and will differ based on the radius of the centrifuge.
RCF - relative centrifugal force, also known as g-force, measures the actual force being exerted.
What is an ultracentrifuge?
Ultracentrifuges are high speed centrifuges that are capable of speeds of around 30,000rpm. These are used in the isolation and purification of membrane components - endoplasmic reticulum, Golgi membrane, DNA, RNA, endosomes, and ribosomes.
Which rotor do I need, fixed or swing out?
Fixed angle rotor - most commonly used rotor. It holds the tubes at a fixed angle, normally 45o. It efficiently pellets samples, however, the pellet is not neat due to the angle of the tube. Fixed rotors are essential when carrying out high throughput methods as the rotor has a larger capacity, and the rotor can withstand a higher centrifugation speed than the swing out, which is needed for macromolecular separation.
Swing out rotor - the rotor swings out horizontally to the axis of rotation. It is made up of buckets and adapters to hold the tubes in place. Any pellets made are neater but the rotor is less efficient at pelleting due to spinning at a lower speed, but the pellet will not get stuck in the ridge of the bottom of the tube. Swing out rotors are designed for when samples are to be resolved in density gradients. These rotors require more maintenance as the pivot requires greasing.
Do I need a high-speed or low-speed centrifuge?
Low-speed centrifuges do not exceed 10,000 rpm and do not require the rotors to be run under a vacuum. The lower speed centrifuges are used mainly to harvest and purify chemical precipitates, intact cells, nuclei, mitochondria and large plasma-membrane fragments. The laboratory centrifuges can separate serum or plasma from red blood cells.
High-speed centrifuges can have speeds up to 21,000 rpm and can require refrigeration systems to overcome the friction heat caused from the spinning rotor, however, they will also require a vacuum. The higher speed centrifuges are used in the separation of cell contents, and in isolating and purifying viruses.
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