Centrifuge Guide

There are many types of centrifuges out there, and they all have their own positives and negatives based on what you need them for. So obviously the first thing you need to know is what you’ll be using your centrifuge for. Centrifuges are commonly used for separation of liquids of various densities or to speed up the sedimentation rate of particles. Below we'll discuss technical aspects of different types of centrifuges to help you determine what centrifuge would be best for you.

Simple centrifuges are used in biology and biochemistry for isolating and separating biocompounds on the basis of molecular weight. These will tend to rotate at a slower rate than an ultracentrifuge, and have larger rotors, as well as being optimized for holding large quantities of material at intermediate acceleration.

Low Speed vs. High Speed

Low speed centrifuges run below 10,000 rpm. They do not require their rotors to run in a vaccum. They are commonly used to separate serum or plasma from red blood cells, and also to harvest and purify chemical precipitates, intact cells, nuclei, large mitochondria, and plasma-membrane fragments.

High speed centrifuges run up to 21,000 rpm, with super speed centrifuges running up to 30,000rpm(rcf 120,000). High speed centrifuges require refridgeration systems to overcome heat generated by the friction of the spinning rotor. They must also incorporate vaccum systems to run properly. High speed centrifuges are mostly used for seperation of cell constituents as well as isolation and purification of viruses.

The Rotor – 3 Basic Designs

Horizontal Operates at up to 3000rpm. It is advantageous in clinical labs(because a flat sediment is produced) and is extremely efficient at low force.

Fixed Angle Operates at up to 7000rpm. Set at a fixed angle to the vertical position.

Vertical Fixed in a vertical position.

The load on the rotor should always be balanced(equal mass and centers of gravity). Don’t ever run the centrifuge with carriers or buckets missing.

Centrifuge Motor

Centrifuge motors are very simple DC motors. Their rotation increases as the voltage increases.

Centrifuge Tubes

It is advisable to use conical-bottomed tubes in a swing-out bucket motor for sedimentation of cells. They retain the pellet of cells more effectively as supernatant is removed.

All tubes used for high speed centrifuges are round bottomed.

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