Centrifuges are essential tools found in almost every laboratory—from clinical and biomedical labs to industrial, academic, and research settings. They are used to separate substances of different densities in a mixture by spinning samples at high speed. While the principle may sound simple, the variety of centrifuge types, rotors, and applications is vast.

Whether you’re new to laboratory equipment or just want to make an informed buying decision, this guide will help you understand what a centrifuge is, how it works, the different types available, and how to use it safely and effectively.

What Is a Centrifuge?

A centrifuge is a laboratory device that spins liquid samples at high speeds. This spinning action generates centrifugal force, which separates components based on their density.

  • Heavier particles (like cells or sediments) move to the bottom of the tube

  • Lighter components (like plasma or supernatant) stay on top

The process is used for sample preparation, purification, and analysis across many scientific disciplines.

How Does a Centrifuge Work?

Centrifuges work on the principle of centrifugal force. When a sample spins around a central axis, heavier components are pushed outward, collecting at the base of the container.

This separation happens in a rotor, which holds sample tubes at a fixed or swinging angle.

Key Terms:

  • RPM (Revolutions per Minute): Speed at which the centrifuge spins

  • RCF (Relative Centrifugal Force): Force applied to the samples (measured in g)

  • Rotor: The spinning platform that holds the tubes

Note: RPM and RCF are related, but not the same. You can calculate RCF using the formula:
RCF = 1.118 × 10⁻⁵ × radius (cm) × (RPM)²

Common Types of Centrifuges

Choosing the right type depends on your application, speed requirements, and sample size. Here are the main types:

1. Microcentrifuge

Used For: Small-volume samples (typically 0.2 to 2 mL tubes), such as DNA/RNA or protein isolation.

  • Compact size

  • Speeds up to 15,000 RPM

  • Used in molecular biology, biochemistry, and clinical labs

✅ Pros: Space-saving, fast spin times
❌ Cons: Not suitable for large volumes

2. Benchtop Centrifuge

Used For: General-purpose applications in clinical or research labs.

  • Can accommodate larger volumes (5–50 mL tubes)

  • Speeds up to 10,000–15,000 RPM

  • Can have interchangeable rotors

✅ Pros: Versatile, commonly used
❌ Cons: Takes up more bench space

3. Refrigerated Centrifuge

Used For: Temperature-sensitive samples like enzymes, blood, or proteins.

  • Maintains temperatures as low as -20°C

  • Prevents sample degradation due to heat

  • Available in benchtop and floor-standing models

✅ Pros: Preserves biological activity
❌ Cons: More expensive than standard units

4. High-Speed Centrifuge

Used For: Larger-volume sample separation at high speed.

  • Speeds up to 25,000 RPM

  • Handles up to 1-liter tubes

  • Ideal for cell harvesting, nucleic acid isolation

✅ Pros: High capacity and speed
❌ Cons: Requires careful balancing and maintenance

5. Ultracentrifuge

Used For: Advanced applications requiring ultra-high-speed separation.

  • Speeds up to 100,000 RPM or more

  • Used in virology, lipoprotein analysis, subcellular fractionation

  • Very high RCF values (up to 1,000,000 × g)

✅ Pros: Precise separation at molecular levels
❌ Cons: Expensive and highly specialized

6. Hematocrit Centrifuge

Used For: Measuring the proportion of red blood cells in blood.

  • Specifically designed to spin capillary tubes

  • Used in clinical diagnostics for anemia or dehydration

✅ Pros: Accurate and dedicated use
❌ Cons: Not suitable for other lab tests

Rotor Types Explained

Rotors determine how your samples are held during centrifugation:

🌀 Fixed-Angle Rotor

  • Tubes held at a 25–45° angle

  • Faster pellet formation

  • Ideal for pelleting cells or precipitates

🧾 Swinging-Bucket Rotor

  • Buckets swing out horizontally during spin

  • Better for separating layers (e.g., blood components)

  • Ideal for gradient separation and large volume tubes

🧲 Vertical Rotor

  • Tubes remain vertical

  • Used in ultracentrifugation and density gradient work

Common Uses of Centrifuges

Centrifuges are used in almost every scientific field. Here are a few examples:

Field Application
Clinical Labs Blood separation (plasma, serum, hematocrit)
Molecular Biology DNA/RNA extraction, protein purification
Microbiology Cell harvesting, bacterial culture separation
Biochemistry Enzyme assays, lipid separation
Pharmaceuticals Drug formulation and analysis
Environmental Labs Water testing and sediment analysis

Tips for Safe and Effective Centrifuge Use

To get the best performance and extend the life of your centrifuge, follow these guidelines:

✅ 1. Always Balance Your Tubes

  • Use tubes of equal weight opposite each other

  • Even slight imbalance can damage the rotor or motor

✅ 2. Use the Right Tubes

  • Choose tubes rated for your RPM/RCF levels

  • Don’t reuse cracked or scratched tubes

✅ 3. Secure the Lid

  • Never operate a centrifuge with an open or unsecured lid

  • Many models won’t spin without lid lock for safety

✅ 4. Start Slow with New Samples

  • Begin with a lower speed and increase gradually

  • This prevents tube breakage or sample loss

✅ 5. Clean Regularly

  • Wipe down rotors and chamber after use

  • Avoid spills of corrosive or biological materials

✅ 6. Service Annually

  • Preventive maintenance ensures smooth operation and long life

  • Check for rotor fatigue or corrosion

Choosing the Right Centrifuge for Your Lab

When selecting a centrifuge, ask yourself:

  • What’s the sample size and volume I’ll work with?

  • Do I need temperature control (refrigeration)?

  • How much bench space do I have?

  • What speed/RCF is needed for my application?

  • Do I need interchangeable rotors for flexibility?

Top global brands to consider include:

  • Eppendorf

  • Thermo Fisher Scientific

  • Hettich

  • Beckman Coulter

  • Remi (popular in Asia)

  • Sigma