By Vvon Engineering Team | Published | Updated
Swing out against fixed angle, why protocols should be written in g rather than rpm, and the tube, adapter and speed limits that a rotor imposes on the instrument it is fitted to.
Medical equipment RFQ checklist (TXT)
Sample preparation depends on the centrifuge, rotor, tubes, timing and handling as a complete method. Haemolysis or poor separation can have several causes; investigate the specimen and protocol before attributing the result to a rotor alone.
Browse the BIOBASE and Infitek centrifuge range alongside the GEMMY catalogue. Supply tube dimensions, sample count, required RCF and temperature conditions. Ask for the rotor, buckets, adapters and any containment accessories as explicit quotation lines. A machine's maximum speed does not establish the capability of every rotor or its suitability for your clinical workflow.
In a fixed-angle rotor, sedimentation follows the centrifugal field and the pellet forms against the tube wall towards its outer end. A swinging bucket becomes horizontal during operation and can form a pellet at the bottom of the tube. Recovery and decanting still depend on the sample and technique.
That difference decides several routine jobs.
The tube manufacturer’s instructions determine the acceptable rotor and centrifugation protocol. For example, BD lists approved swinging-bucket and fixed-angle conditions for specified SST/PST gel tubes, while Barricor tubes require a swinging-bucket rotor. Do not generalise one tube’s requirements to every separator tube. Compare sample quality, compatible adapters and workflow, not a blanket claim that one rotor is always faster or quieter. Where aerosols are a concern, select appropriate containment and follow the biosafety procedure for loading and opening.
Revolutions per minute describes how fast the motor turns. Relative centrifugal field describes what the sample experiences, and it depends on the rotating radius as well as the speed. The same 3,000 rpm on a small rotor and on a large one are two different treatments of the sample.
The relationship is fixed and worth having on the wall: relative centrifugal field in units of gravity equals 1.118 times ten to the power minus five, multiplied by the rotating radius in centimetres, multiplied by the square of the speed in revolutions per minute. Because speed is squared, small differences in setting matter more than people assume, and because radius is a straight multiplier, changing rotor changes everything.
Changing the rotor can alter sedimentation, tube support, braking and sample quality even at the same calculated RCF. Use the specified radius and tube instructions, then verify or revalidate the preparation method as required by the laboratory’s quality system. Updating the RPM conversion table alone may be insufficient.
Note also which radius the manufacturer quoted. Maximum radius at the bottom of the tube and the radius at the middle of the sample give different answers, and a specification that does not say which one it used is a specification to query rather than to trust.
A centrifuge does not have one maximum speed. It has a maximum speed for each rotor, and often a lower one again with particular buckets, adapters or tube types fitted. That derating is printed on the rotor or in the manual, and running above it is not a performance advantage, it is a failure waiting for a witness.
For a proposed GEMMY PLC-012, PLC-025 or other centrifuge, request the current datasheet and the exact rotor/adapter combination. Verify maximum RCF, tube compatibility, usable capacity, lid controls and any imbalance protection on that configuration; do not assume every model has the same safety functions.
Before the next purchase, do one piece of paperwork: list every tube type the laboratory spins, the force and time each protocol calls for, and the number of each at the busiest hour. Take that list to the supplier and specify the rotor from it. The instrument that suits the list is usually obvious once the list exists, and it is frequently not the one with the highest speed on the front of the brochure.
Confirm the current instructions for the exact tube catalogue number before setting the laboratory procedure. Manufacturer example: BD Vacutainer SST product and centrifugation guidance.
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