Centrifuge tubes are rated by the maximum RCF or G force they can withstand without cracking or, in the case of plastic centrifuge tubes, deforming. Centrifuge tubes are specifically designed to withstand the relative centrifugal force created when spinning in a centrifuge. You cannot spin test tubes or culture tubes in a centrifuge whether they are plastic or glass as these will be either deformed or cracked under the stress. The g forces created in a centrifuge are quite high, 200 to 1800 x g in a clinical centrifuge found in a doctor’s office. The forces are much higher in research centrifuges: 6000 to >200,000 x g.
The controls on the centrifuge determine the speed (rpm) but the rotor determines the rcf. The rcf depends not only on the rotational speed of the rotor but on the radius as measured from the center of the rotor to the point where the tube rests in the rotor.
Centrifuge tubes range in volume from 0.2ml PCR tubes to 500ml Centrifuge bottles. The plastic microcentrifuge tubes, 0.2ml PCR and 1.5/2.0ml, are designed to withstand approximately 20,000 to 30,000 x g. Plastic blood tubes, ranging in size from 2.5ml to 10ml, are designed for about 2000 x g. Polypropylene 15ml and 50 ml centrifuge tubes have a maximum rcf of approximately 17,000 x g. Plastic centrifuge bottles – 250ml; 500ml; 1l – maximum rcf ranges from approximately 8000 to 27,000 x g. Each manufacturer has determined the maximum rcf for their tubes and bottle and should be consulted if the protocol requires spinning at speeds near the maximum for the rotor chosen.