Centrifuges

FAQs

• What are some common applications in labs on a fixed-angle rotor vs a swing-out rotor on a high-speed centrifuge?

  Fixed-angle rotors are commonly used in fast, high-force pelleting and routine general separation across a range of typically used sample tubes and volumes. This includes separation of DNA, RNA, and protein precipitates from debris and particulates in diverse samples, including from tissue lysis, as well as harvesting of cells such as bacteria, yeast, and organelles if sample mixing / clear layers are non-critical.

  Swing-out / swinging-bucket rotors typically leverage lower and gentle speeds or centrifugal force than fixed-angle rotors for applications that benefit from clean, flat layers with minimal smearing and clearer separation and gradients. Common uses include separation of blood into plasma or serum and buffy coat for downstream pipetting, gentler cell pelleting and harvesting from tissue cultures or tissues for viability, as well as an expanded versatility for larger-volume vessels or microplates.

  Mini, low-speed, and ultracentrifuges also exist to round out more limited or specialized applications on top of high-speed centrifuges. Depending on the need, labs choose from a diverse selection, and rotors and other accessories are essential to workflows that depend on proper centrifugation for downstream applications that require a clean analyte as a starting point.

• What considerations are given for selecting tubes/materials for high-speed centrifuges?

  Common materials include plasticware made from a variety of plastic materials (PP, PS, PE, etc) as well as glass, that can differ in clarity, chemical or impact resistance, or temperature tolerance. Considerations should be made for material handlings pre-centrifugation (such as bead-beating of tissues, long-term storage at -80°C or -20°C, chemical/buffer addition, etc.) and maximum allowable force during centrifugation when setting up protocols on centrifuges with appropriate consumables.

• What is RCF vs RPM and how are they related?

  RCF stands for relative centrifugal force while RPM stands for revolutions per minute. RCF indicates the actual force applied to the sample and is measured or denoted as x g (interchangeable and expressed as a multiple of Earth's gravity) in protocols. In the same vein, RCF and g-force are commonly treated synonymously. RCF is dependent on the rotor radius while RPM is the rotor's speed. For example, two centrifuges at the same RPM may deliver different forces, so many protocols use RCF for this reason, though most centrifuges have built-in conversion for ease of translatability between these measurements during their program setup on the centrifuge.

• What are some common precautions to take before running a centrifuge?

  Some causes for unusual noise, vibration/shaking/wobbling, or issues with centrifuges can include the following:

  • Balancing the rotor load, make sure to use similar weight balance tubes if needed or that tubes are spaced evenly around the rotor.
  • Ensure centrifuge is on a sturdy, level bench or surface; always close centrifuge lids securely before use and allow centrifuge to reach or is at a full stop before opening. Also confirm buckets or biocontainment lids are fully sealed as intended before starting.
  • Tube deformation or leaking due to cracking, improper sample volumes, etc. Inspect tubes before use.
  • Rotor misalignment, loose rotors, loose lids, incomplete locking mechanism
  • Worn bearings or other mechanical parts from overuse or unintended use
  • Debris or obstruction under rotor

  These are important checks to perform as the life of a centrifuge and rotor can be impacted by repeated vibrations. Common unintended mishaps in the lab range from small to major cleaning or loss of irrecuperable samples, so it may be good practice to build in a good habit of checking some basic items before starting a run.

• What are some routine maintenance steps labs can perform to clean and maintain a centrifuge in good order?

  Some considerations to help rotor and centrifuge lifetime include the following:

  • Make sure users are aware of how to operate the centrifuge. This includes proper seating of buckets in pins, balancing, abiding by recommendations of speed and maximum mass/volumes, not moving the centrifuge while in use, rough handling, and avoiding scratching of rotor and other critical components. Confirm users are familiar with signs of wear to pay attention to and bring up.
  • Wiping rotors and accessories with neutral cleaning or disinfectant solutions with a soft cloth. Wiping down interior portions of the centrifuge, rotor chamber, as well as surfaces on and around the centrifuge station at a routine frequency.
  • Spot check to make sure there are no spills or chemical exposure that may require additional protocols for cleaning of rotors or centrifuge. This may also help minimize risk of cross-contamination, especially for high-frequency usage amongst many equipment users or projects, etc.