Centrifuge Settings and What They Protect

Part of Clinical Laboratory (LAB) Training: Processing to the Laboratory Manual.

About 2 minutes. Free, in your language, no account needed.

The numbers do specific work

Speed, time, temperature and brake are each specified for a reason. Changing one changes what comes out of the tube.

Speed is specified in g, not rpm

Relative centrifugal force depends on the rotor radius as well as the speed. The same rpm in two different centrifuges produces different g.

If the manual gives g and your instrument is set in rpm, convert using your rotor's radius. Do not assume the previous user's setting was right for this study.

Record what you actually ran.

Temperature changes the result

Many analytes require a refrigerated spin. Others must be at room temperature. Spinning a cold-sensitive analyte at 4 degrees can alter it before the assay ever runs.

Confirm the chamber temperature, not just the setting on the dial.

The brake matters more than it sounds

A hard stop can resuspend a pellet that separated correctly. For some cell preparations the manual will specify brake off.

If it does, that is because the separation is fragile, not because somebody preferred it.

Time is a minimum, not a target

Under-spinning leaves the fraction incompletely separated. Over-spinning is usually less harmful but is still a departure from the manual and still recorded.

Hemolysis is the visible failure

A pink or red plasma layer means red cells have ruptured. Potassium, LDH and several other analytes rise sharply, and the result is not usable for those tests.

Hemolysis can come from the draw, from rough handling, from the wrong needle gauge or from over-spinning. It is not always the laboratory's doing.

Record it when you see it, grade it if the manual asks you to, and query rather than reporting quietly.

What to write down

The instrument used, the actual speed, the actual time, the temperature and the operator.

Written at the time. A log completed at the end of the day from memory is a reconstruction, and it will read as one.