How does a laboratory centrifuge work?

A laboratory centrifuge is a device that uses centrifugal force to separate components in a liquid sample based on their density. When the centrifuge spins at high speeds, denser materials move outward toward the bottom of the tube, while lighter substances remain at the top.

Key Principles of Centrifugation:

• Centrifugal Force: Rapid rotation generates force, pulling denser particles outward.

• Density-Based Separation: Components separate according to size, shape, and mass.

• G-Force (Relative Centrifugal Force, RCF): Determines separation efficiency and depends on both speed (RPM) and rotor radius.

Common Applications:

• Biological Research: Separating blood plasma, cell fractions, and proteins.

• Clinical Diagnostics: Isolating serum or DNA for medical testing.

• Chemical Studies: Separating precipitates from solutions in industrial labs.

What is the difference between a fixed-angle and swing-bucket rotor?

The rotor is the spinning component inside a centrifuge that holds the sample tubes. Choosing the right rotor type depends on separation needs and sample volume.

Which one should you choose?

• For quick pelleting and high-speed separations, use a fixed-angle rotor.

• For large volumes, layering-based separations requiring a uniform pellet at the bottom, use a swing-bucket rotor.

How do I balance my centrifuge properly?

Balancing your centrifuge is essential for safety and accuracy. An unbalanced centrifuge can cause vibrations, rotor damage, or inaccurate results.

Step-by-Step Guide to Proper Balancing:

1. Evenly distribute sample tubes: Place tubes with equal volume and weight opposite each other.

2. Use a balance tube if needed: If running an odd number of samples, add a tube with an equal volume of liquid as a counterbalance.

3. Ensure symmetrical placement: If using a four-slot centrifuge, place tubes in a cross pattern rather than side-by-side.

4. Double-check weight differences: Variations greater than 0.1 grams can impact performance at high speeds.

5. Secure lids and verify rotor positioning: Improperly secured tubes may break, leading to sample contamination or equipment damage.

A properly balanced centrifuge prevents mechanical wear, extends lifespan, and ensures accurate sample separation.

What RPM and G-force settings should I use?

The RPM (Revolutions Per Minute) and G-force (Relative Centrifugal Force, RCF) required for an experiment depended on the sample type and separation goals.