Choosing a clinical centrifuge: matching swing-out and fixed angle centrifuge rotors to tube types and to the separation you need, why relative centrifugal force rather than speed is what a protocol specifies, and the containment a clinical sample demands

Choosing the instrument and the rotor

1. Specify in relative centrifugal force, never in revolutions. The force a sample experiences depends on the rotor radius as well as the speed, so the same revolutions per minute in two rotors give different separations. Protocols are written in relative centrifugal force, and a laboratory converting on the fly will eventually get it wrong.
2. Choose swing-out for separated layers, fixed angle for pellets. A swing-out rotor gives a horizontal, flat interface, which is what a serum or plasma separator tube needs and what makes a clean draw possible. A fixed angle rotor packs a tight pellet against the tube wall and is faster and more compact.
3. Match the buckets and adaptors to the exact tubes. Blood collection tubes vary in length and diameter between manufacturers, and adaptors are rotor-specific. A rotor that does not take your tubes without a wobble will break them, and tube breakage in a clinical laboratory is a containment event.
4. Decide refrigeration from what you spin. Cell separations and anything where analyte stability depends on temperature need refrigeration. For routine serum separation at ambient it is a cost without a benefit, and refrigerated instruments are larger and noisier.
5. Take containment seriously for clinical samples. Sealed buckets or a sealed rotor that can be opened inside a biosafety cabinet are what turn a broken tube from an aerosol release into a contained spill. For potentially infectious material this is the specification that matters most.

Balance, and the failure it prevents

Loading opposite positions with equal mass is the whole of balancing, and imbalance detection is a backstop rather than a substitute. A visibly shaking centrifuge should be stopped, not waited out.

Where an odd number of tubes is unavoidable, a water-filled blank of matched mass is the answer. Laboratories that improvise here eventually damage a rotor.

Pre-analytical effects nobody records

Time to centrifugation, spin time, force and temperature all affect analyte concentrations, particularly for cell-associated markers and unstable analytes. Fix them in the procedure and record deviations, because these variables move results more than most people expect.

Where samples arrive from several collection sites, harmonise the centrifugation step explicitly. It is one of the largest sources of between-site variation in multi-centre studies.

Siting and noise

Centrifuges vibrate and are noisy, and a bench shared with a balance is a bench where the balance never settles. Put them on their own solid bench away from precision instruments.

Leave the clearance the manufacturer specifies around the unit. Restricted airflow shortens the life of the drive and, on a refrigerated instrument, means it never reaches temperature.

Common questions

Swing-out or fixed angle centrifuge?

Swing-out for separated layers and gel separator tubes, because the interface forms flat and a clean draw is possible. Fixed angle for pellets, where it packs tighter, spins faster and takes less bench space.

Why do protocols specify RCF rather than rpm?

Because the force depends on rotor radius as well as speed. The same revolutions per minute in a large and a small rotor produce different separations, so the force is the transferable number and the speed is not.

What containment does a clinical centrifuge need?

Sealed buckets or a sealed rotor that can be carried into a biosafety cabinet and opened there. A tube breaking in an unsealed rotor releases aerosol into the room, which is the event the sealing exists to prevent.

How often should a centrifuge be serviced?

Annually as a minimum, with rotor inspection for corrosion and fatigue and a check of the lid interlock and the imbalance detection. Rotors have documented service lives and a failed rotor at speed is a serious hazard.

Browse by service class

• Compare Gene synthesis on advertised prices