Centrifuge Tube: Definition, Function, How It Works, and Types
In the world of laboratory science, precision and safety are paramount. Among the many tools that enable researchers to separate, analyze, and store samples, the centrifuge tube stands out as a quiet workhorse. Though simple in appearance, this tube plays a critical role in biological, chemical, and clinical research.
What Is a Centrifuge Tube?
A centrifuge tube is a specialized container designed to hold liquid samples during centrifugation, a process that uses rapid spinning to separate substances based on density. These tubes are typically made of plastic (polypropylene or polyethylene) or glass, and they come in various sizes, most commonly 15 mL and 50 mL.
The defining feature of a centrifuge tube is its conical bottom, which allows denser particles to collect neatly at the tip after spinning. This design makes it easier to isolate and extract specific components from a mixture.
Function and Purpose
Centrifuge tubes are used in a wide range of laboratory procedures, including:
- Separating blood components (e.g., plasma, red cells)
- Isolating DNA or RNA from biological samples
- Purifying proteins or enzymes
- Clarifying solutions by removing particulates
- Storing samples before or after processing
Their durability and chemical resistance make them suitable for high-speed centrifugation and exposure to reagents.
How Does a Centrifuge Tube Work?
The principle behind centrifugation is simple: when a sample is spun at high speed, centrifugal force pushes heavier particles outward and downward. In a centrifuge tube, this means:
- Sample is loaded into the tube.
- Tube is placed in a centrifuge rotor, balanced with a tube of equal volume opposite it.
- Centrifuge spins, often at thousands of revolutions per minute (RPM).
- Heavier particles settle at the bottom (pellet), while lighter substances remain above (supernatant).
After spinning, the tube can be carefully removed, and the desired layer extracted using a pipette.
Types of Centrifuge Tubes
Centrifuge tubes vary based on material, size, and application:
| Type | Description |
|---|---|
| Conical tubes | Most common; tapered bottom for easy pellet collection |
| Round-bottom tubes | Used in ultracentrifugation; less common in routine labs |
| Microcentrifuge tubes | Small (0.5–2 mL); used in molecular biology and DNA extraction |
| Glass tubes | Ideal for chemical resistance; used in high-speed or heat-sensitive tasks |
| Screw-cap tubes | Provide secure sealing; prevent leakage during spinning |
| Snap-cap tubes | Easy to open and close; suitable for quick procedures |
Each type is chosen based on the sample volume, centrifuge speed, and chemical compatibility.
Frequently Asked Questions
What is the centrifuge tube used for?
A centrifuge tube is used to hold liquid samples during centrifugation, allowing separation of components based on density—such as isolating plasma from blood or purifying DNA from cell lysates.
What is another name for a centrifuge tube?
Centrifuge tubes are sometimes called centrifugal tubes, conical tubes, or Eppendorf tubes (especially in reference to small microcentrifuge tubes).
How to put 5 tubes in a centrifuge?
Always balance the rotor. If using 5 tubes, add a sixth tube with an equal volume of liquid opposite the fifth to maintain symmetry. Uneven loading can damage the centrifuge or cause inaccurate results.
Which tube goes in the centrifuge?
Any tube designed for centrifugation can be used, provided it matches the rotor size and speed rating. Common choices include 15 mL or 50 mL conical polypropylene tubes for general lab use.
What are the different types of centrifuge tubes?
Types include conical tubes, round-bottom tubes, microcentrifuge tubes, glass tubes, screw-cap tubes, and snap-cap tubes. Each serves a specific purpose depending on sample type and centrifuge specifications.
What is the liquid in a centrifuge tube called?
The liquid is typically referred to as the sample before spinning. After centrifugation, it separates into the supernatant (top layer) and pellet (bottom layer), depending on the density of its components.
