3.3.3 Care and maintenance of centrifuges
Corrosion and degradation due to biological buffer systems used within rotors or
contamination of the interior or exterior of the centrifuge via spillage may seriously
affect the lifetime of this equipment. Another important point is the proper balancing
of centrifuge tubes. This is not only important with respect to safety, as outlined
below, but might also cause vibration-induced damage to the rotor itself and the drive(a)(b)(c)Centrifugal fieldCentrifugal fieldCentrifugal fieldFig. 3.3Operation of the three main types of rotors used in routine biochemical centrifugation techniques.
Shown is a cross-sectional diagram of a centrifuge tube positioned in a fixed-angle rotor (a), a vertical tube
rotor (b), and a swinging-bucket rotor (c). The diagrams illustrate the movement of biological samples
during the initial acceleration stage, the main centrifugal separation phase, de-acceleration and the final
harvesting of separated particles in the rotor at rest. Using a fixed-angle rotor, the tubes are filled with a gradient,
the sample loaded on top of this solution and then the tubes placed at a specific fixed-angle into the rotor cavities.
The sample and the gradient undergo reorientation in the centrifugal field during rotor acceleration, resulting
in the separation of particles with different sedimentation properties. Similar reorientation of gradients and
banding of particles occurs in a vertical rotor system. A great variety of gradients can be used with swinging-
bucket rotors, making them the method of choice when maximum resolution of banding zones is required.84 Centrifugation