Benchtop Centrifuge Selection Guide
A centrifuge is an essential piece of equipment in almost any life science and clinical laboratory and with the right consideration certain models can prove to be very versatile for across many applications. Here we list some key points to think about when you are deciding on the right bench top centrifuge to purchase for your lab:
Required Size (Capacity and footprint)?
What maximum speed is needed?
What vessels are you spinning - what rotor type will accomadate them?
Does it need to be refrigerated or heated?
Does it need IVD certification?
Size - Capacity & Footprint
Bench space is a premium in many labs so you are probably looking for the best mix of functionality, tube capacity and physical footprint. Broadly, benchtop centrifuges are categorised according to their size and capacity and come in in three types (in increasing size and capacity) - Mini centrifuge, Micro centrifuge, Multi purpose centrifuge.
- Small capacity
- Generally accepts 0.5/2.0ml tubes
- Usually fixed rotor or only a choice of a few
- Lower speed
- May also fall into the Micro centrifuge category
- Ideal if you are processing a small number of tubes and want to stick to the same method every time.
- Medium capacity
- Typically will accept tubes up to around 5.0ml and some will accept blood/urine tubes
- Often a selection of rotors and tube adapters available
- Some models can come refrigerated
- Great for higher throughput application of small tubes, and also clinical applications
- Larger capacity
- It varies greatly between models but they can accept tube sizes up to around 750ml
- Large selection of rotors (including fixed angle and spin out) and adapters meaning they can accept the largest number of different tubes but also other vessels including multi well plates
- Many models come as a refrigerated or non-refrigerated variants
- Perfect for high throughput applications and methods involving the use of large tubes and sample volumes
Additionally, there are other centrifuges available on the market that are larger and can be more specialised including free and floor standing centrifuges and ultracentrifuges, however Camlab does not supply these types.
The maximum speed that a centrifuge will reach is a vitally important factor when choosing the best option for your application and methods. But something that is maybe less thought about is the increments of the speed setting and how accurate the speed needs to be. Rotor and tube type will impact on the max speed at which the centrifuge can be operated and should be considered along with the max speed of the centrifuge itself. Some centrifuges feature an automatic rotor recognition, limiting the speed of the centrifuge automatically in line with the rotor.
In centrifuges, speed is summarised by two measures - the RPM (or rototations per minute) and RCF (or relative centifugal force measured in force x gravity). You can read a more in depth post on the differences between the two here, but often methods with detail the required speed in RCF. If you are upgrading a current centrifuge and only know the RPM, you will want to calculate it's RCF to be able to choose an appropriate new model.
Rotors and Adapters
Small centrifuges such as mini centrifuge models will often not have the ability to change between rotors- they are known as fixed rotor models. In centrifuges with changeable rotors, usually you are to purchase the rotor separately to the centrifuge itself. Certain manufacturers may offer bundles containing the rotor and any neccessary adapters to accept commonly used tube types. There are two types of rotor available with each having different pros and cons depending on your application. We sum up the key features to help you decide which is the best choice:
Fixed Angle Rotors
- Fixed angle rotors are the most common type you will see in a lab. They hold your tubes at a fixed angle (usually 45 degrees).
- They can withstand a higher centrifugation speed than their swing out counterparts which is necessary for macromolecule separation. Due to this, they efficiently pellet samples - however due to the angle of the tubes, the pellet is not neat and will be at the bottom and up the bottom side of the tube.
- They will also have a larger capacity - esssential for any high throughput applications.
Swing Out Rotors
- Swing out rotors, as the name suggests, swing out horizontally to the axis of rotation.
- They work with a combination of buckets and adapters to hold tubes in place.
- They spin at lower speeds meaning pelleting is less efficient but the pellet they create will be more neatly at the bottom of the tube, and doesn't get caught in the ridge of the bottom of the tube.
- Designed for applications when samples are to be resolved in density gradients.
- Require a little extra maintenance - the pivot should be adequetly greased.
Ease of rotor changes
Some rotors require a key to change between them and for most this may be trivial however if you have ever lost the key you will understand the frustration! Whilst this may not be a key factor in your decision, some centrifuges have easy rotor changes, without the need for rotor keys.
Refrigerated, Non-refrigerated and Heated
Centrifuge models may be available refrigerated meaning they have cooling in the centrifuge chamber itself to protect heat-sensitive samples. Refrigerated centrifuges will sometimes have heating ability meaning they can maintain a higher than ambient chamber temperature. A small number of heated centrifuges are also on the market and will heat to an even greater temperature. However, the refrigeration unit takes up quite a bit of space and refrigerated models will be larger in size than their non-refrigerated counterparts. The refrigeration unit may be located on the back or side of the centrifuge.
Getting the chamber down to the correct temperature can be quite time consuming depending on the model. A handy feature that some centrifuges having is a pre-cooling function, the chamber is cooled prior to use. This will be an important feature if your samples are very heat sensitive.
Rate of temperature changes
The speed at which the set temperature is reached may be something you want to consider. Some models are available with quick cooling options offering a more speedy way to reach your desired temperature.
Centrifuges with IVD certification are registered as an in vitro diagnostic medical device under the IVD Directive 98/79/EC in Europe. If your lab is involved in clinical work, then you will probably be looking at getting a centrifgue with this certification. Some manufacturers produce whole ranges of centrifuges with IVD certification aimed at clinical applications such as the Hettich range whereas other manufacturer may offer IVD versions of their centrifuges to complement their general lab ranges, such as Eppendorf. Having this certification may come at a price premium. You can view our range here.
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The information provided is intended as a guide, please check exact product manuals and contact us if you are unsure on anything.