How fast does a centrifuge spin

However, many centrifuges display speed as revolutions per minute RPM , necessitating conversion to ensure the correct experimental conditions. Floor-standing models offer greater sample capacity and can achieve high speeds.

Superspeed centrifuges can achieve a maximum g -force relative centrifugal force, RCF of over 70, x g , and ultracentrifuges often used for DNA or RNA fractionation, can achieve up to 1,, x g.

For large-capacity, low-speed applications, low-speed centrifuges reaching approximately x g are available. Benchtop models have a smaller footprint, and general-purpose models are ideal for a wide range of applications. There are many benchtop models available, including high-speed, microcentrifuge, clinical, and cell washer models. Clinical benchtop models and cell washers typically operate at lower speeds, and are suited to diagnostic applications, and washing debris from red blood cells.

It is essential to select a centrifuge that is suited to the specific application. When purchasing a centrifuge, it is important to consider the following questions:. Running an unbalanced centrifuge may cause significant damage, and injure the operator and other laboratory personnel.

The total mass of each tube should be as close as possible- this becomes increasingly important at very high rotor speeds. Balancing masses to the nearest 0. For example, do not balance a sample consisting of liquid with a higher or lower density than water with an equal volume of water. A little vibration is normal, but excessive amounts can mean danger. First, double check that the tubes are correctly balanced.

If this does not resolve the issue, do not operate the centrifuge until it has been serviced by the manufacturer or dealer. RCF is the preferred method of measurement as it will remain the same even if you are using a different centrifuge with a different rotor size. A centrifuge spinning at RPM, for example, will spin at RPM regardless of the centrifuge being used or the size of the rotor. RCF accommodates the rotor size into its measurement so we can determine the gravitational force being applied.

You may notice that your centrifuge only has a setting for RPM. If you are currently in the market for a centrifuge, try to find one that measures both RPM and RCF to save you having to manually convert them. Most modern centrifuges will have this functionality where you can simply switch between the two interchangeably.

The formula below allows you to convert RPM to RCF but the issue with using this formula is that you have to determine the radius. During phase separation, chemicals are converted from a matrix or an aqueous medium to a solvent for additional chemical or molecular biological analysis. In ultrafiltration, macromolecules are purified, separated, and concentrated by using a membrane.

Isopycnic centrifugation is carried out using a "self-generating" density gradient established through equilibrium sedimentation. This method concentrates the analysis matches with those of the surrounding solution. Protocols for centrifugation typically specify the relative centrifugal force rcf and the degree of acceleration in multiples of g g-force.

Working with the rotational speed, such as revolutions per minute rpm , is rather imprecise. In general, applications for centrifugation specify the degree of acceleration to be applied to the sample rather than specifying a specific rotational speed such as revolutions per minute.

The distinction between rpm and rcf is important, as two rotors with different diameters running at the same rotational speed rpm will result in different accelerations rcf. As the motion of the rotor is circular, the acceleration force is calculated as the product of the radius and the square of the angular velocity.

As mentioned, when using rotors with different radii for centrifugation, the same rcf g-force should be used. Both centrifuges can spin a rotor with 1. To make life easier and to better reproduce the data, some centrifuges have buttons directly on the operating panel for automatic conversion between rpm and rcf. If your centrifuge does not have an rpm-rcf converter, you may use the formula, the rpm-rcf converter found on the homepages of centrifuge suppliers, or a nomogram for conversion.

The k-factor is a parameter for the sedimentation distance in a test tube. This factor is also called clearing factor and represents the relative pelleting efficiency of a centrifugation system at maximum rotational speed.

In general, the k-factor value is used to estimate the time, t in hours , required for complete sedimentation of a sample fraction with a known sedimentation coefficient measured in s svedberg. A small k-factor represents a more rapid separation. The value of the k-factor is primarily determined by the rotor diameter.

Especially for ultracentrifugation, the k-factor is still relevant. If you follow a given protocol, make sure to use the same type of rotor and apply the given relative centrifugal force rcf as well as the same temperature and running time. In general, the following major parameters have to be determined for a successful centrifugation run:. The most common rotors in laboratory centrifugation are either fixed-angle or swing-bucket rotors.