Revolutions per minute [RPM] vs Relative centrifugal force [RCF] in the Safety Centrifuge

Revolutions Per Minute (RPM) and Relative Centrifugal Force (RCF) are important abbreviations used while using a centrifuge. However, these terminologies differ from each other.

RPM vs. RCF (g force)

• RPM indicates the speed at which the rotor is rotating.
• RCF is the term used to describe the amount of accelerative force applied to a sample in a centrifuge.
• RCF is measured in multiples of the standard acceleration due to gravity on the Earth’s surface (x g).
• This is why RCF and “x g” are used interchangeably in centrifugation protocols.
• The two variables that describe RCF are the radius and the angular velocity of the rotor, i.e., how wide the rotor is and how fast it is moving.
• RCF is more precise than RPM because the rotor size might differ, and RCF will be different, while the revolutions per minute stay the same.

Calculating RCF required from the known RPM value

Formula: 

RCF = 1.1118 x 10 ^-5 x r x   rpm2 

r = radius in cm from the centrifuge spindle to the bottom end of the tube

RCF = desired centrifugal force

A nomogram, provided by the manufacturer, can be used to convert RPM to RCF value.

Resources

• Global Laboratory Initiative Training Package on LC.

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