How to Properly Use Centrifuge Tubes？

Centrifuge tubes are one of the most essential consumables in modern laboratory workflows. They are widely used in sample preparation, molecular biology, clinical diagnostics, and environmental testing. Although centrifuge tubes are simple in structure, improper usage can lead to sample loss, contamination, tube deformation, or even experimental failure. Therefore, understanding how to properly use centrifuge tubes is critical for ensuring experimental accuracy and reproducibility.

What is a centrifuge tube？

A centrifuge tube is a container used to hold samples during centrifugation. It is usually conical or round-bottomed and can be used with a centrifuge to separate the components of a mixed liquid using centrifugal force at high speed. Centrifuge tubes have the following basic features:

• High mechanical strength: Need to withstand the huge centrifugal force when the centrifuge is running.
• Good sealing performance: Prevent sample leakage or contamination during centrifugation.
• Strong chemical stability: Resistant to a variety of acids, alkalis and organic solvents.
• Transparent or translucent material: Convenient to observe the state of the sample.

Centrifuge tubes come in a variety of sizes and capacities, from 0.2mL microcentrifuge tubes to 50ml conical tubes, which are widely used in different experimental needs.

How Are Centrifuge Tubes Classified?

How are centrifuge tubes classified in laboratories based on capacity, material, bottom shape, and cap type? What are the differences between each category?

Centrifuge tubes can be classified in several ways depending on laboratory requirements. The most common classification includes capacity (volume), material, bottom shape, and cap design. Each type is designed for specific applications to ensure safety, performance, and experimental accuracy.

• Classification by Capacity

Centrifuge tubes are commonly divided into three main categories based on volume.

1. Microcentrifuge Tubes: 0.5 mL, 1.5 ml centrifuge tubes, 2 ml centrifuge tube, used for small-volume molecular biology experiments.

2. Standard Centrifuge Tubes: 5 mL, 10mL, 15ml centrifuge tube, 50ml centrifuge tubes, most commonly used in general laboratory workflows.

3. Centrifuge Bottles(Large Volume CentrifugeTubes): 175 mL – 500 mL, designed for large-scale sample processing. 

• Classification by Bottom Shape

The bottom design affects sample collection efficiency after centrifugation.

1. Conical Centrifuge Tubes: Most common design, easy pellet collection.

2. U Bottom Tubes: Smooth curved bottom, gentle sample handling.

3. Self-Standing Tubes: Flat reinforced bottom,can stand without rack.

• Classification by Cap Type

Cap design affects sealing performance and contamination risk.

1. Flip-Top (Snap Cap) Centrifuge Tube: Easy one-hand operation, quick opening and closing.

2. Screw Cap Centrifuge Tubes: Strong sealing performance, leak-proof design, suitable for long-term storage. 

• Classification by Material

Centrifuge tubes can be broadly classified into plastic centrifuge tubes and glass centrifuge tubes. Each material offers unique advantages and is suitable for different laboratory applications.

Plastic Centrifuge Tubes: Plastic centrifuge tubes are the most widely used type in modern laboratories. They are lightweight, durable, resistant to breakage, and suitable for routine biological and chemical experiments. Most plastic centrifuge tubes are manufactured from high-performance polymers such as polypropylene centrifuge tubes.

Glass Centrifuge Tubes: Glass centrifuge tubes are primarily used in specialized laboratory applications where plastic materials may not be suitable. They provide excellent resistance to many organic solvents and do not react with most chemicals, making them ideal for analytical chemistry and solvent-based experiments.

How to Choose the Right Centrifuge Tube？

Selecting the correct centrifuge tube is a critical step to ensure experimental accuracy, sample integrity, and safe operation during centrifugation. Different applications require different tube specifications, so careful selection is essential.

• Sample Volume 

The first and most basic factor is the sample volume. Centrifuge tubes are available in a wide range of capacities such as 0.5 mL, 1.5 mL, 2 mL, 5 mL, 15 mL, and 50 mL centrifuge tubes.

Always choose a tube with slightly larger capacity than the actual sample volume. This helps prevent overflow during mixing or centrifugation and reduces the risk of contamination or sample loss.

If the tube is overfilled, it may lead to leakage or imbalance during centrifugation, while an oversized tube may increase unnecessary reagent usage.

• Centrifugal Force (RCF Rating)

Each centrifuge tube has a maximum relative centrifugal force (RCF) rating, which indicates the highest speed it can safely withstand.

For high-speed or ultracentrifugation applications, it is essential to choose tubes with reinforced walls and high RCF resistance. Using an unsuitable tube may result in cracking, deformation, or sample leakage, which can compromise experimental results and safety.

Always check the manufacturer’s specification and ensure compatibility with your centrifuge settings.

• Chemical Compatibility

Different experiments involve different chemicals, including acids, bases, organic solvents, enzymes, or chaotropic salts.

Polypropylene (PP) tubes are commonly used due to their broad chemical resistance, while polyethylene (PE) tubes may be used for specific applications. For highly aggressive solvents or special reagents, it is necessary to verify chemical compatibility before use.

Incorrect material selection may cause tube deformation, cracking, or sample contamination.

• Sterility Requirements

For applications in cell culture, molecular biology, clinical diagnostics, and microbiology, sterile centrifuge tubes are essential.

Sterile tubes are typically treated by gamma irradiation or ethylene oxide sterilization and are certified DNA/RNA-free, DNase-free, and RNase-free. This ensures no biological contamination affects experimental results.

Non-sterile tubes are suitable for general laboratory use but should not be used in sensitive biological applications.

• Temperature Resistance

Many experiments require extreme temperature conditions, such as -80°C ultra-low temperature storage or high-temperature incubation and thermal cycling.

High-quality centrifuge tubes must maintain structural stability under these conditions without becoming brittle or deformed. PP tubes generally offer good low-temperature resistance, making them suitable for cryogenic storage.

It is important to confirm the working temperature range before selecting the tube.

Step-by-Step Guide to Using Centrifuge Tubes

Proper use of centrifuge tubes is essential to ensure experimental accuracy, prevent sample loss, and maintain laboratory safety. The following step-by-step guide outlines the correct operating procedure.

• Step 1: Sample Preparation 

Before loading the sample into the centrifuge tube, ensure that the sample is fully prepared and evenly mixed. This is especially important for biological samples, suspensions, or solutions containing particles.

Proper mixing helps ensure sample consistency and improves the reliability of downstream experimental results. Vortexing or gentle inversion can be used depending on sample type.

• Step 2: Tube Loading

Use a pipette or transfer device to carefully load the sample into the centrifuge tube. Avoid splashing or contamination during transfer.

Do not overfill the tube. It is recommended to leave sufficient headspace to prevent overflow or leakage during centrifugation, especially in high-speed applications.

• Step 3: Proper Balancing 

Balancing is one of the most critical steps in centrifugation. Tubes must be placed in the rotor in balanced pairs with equal weight.

Even small differences in weight can cause vibration, rotor damage, or instrument failure. For best results, use an analytical balance when working with small volumes or high-speed centrifugation.

• Step 4: Secure Sealing

Ensure that the centrifuge tube cap is tightly closed before starting centrifugation. A loose cap may result in leakage, sample loss, or aerosol contamination.

For biological or hazardous samples, proper sealing is essential to maintain biosafety and prevent cross-contamination.

• Step 5: Centrifugation Settings 

Set the appropriate centrifugation speed based on experimental requirements, usually expressed as RPM (revolutions per minute) or RCF (relative centrifugal force).

Always ensure that the selected centrifuge tube is rated to withstand the required RCF. Exceeding the maximum speed may cause tube deformation or rupture.

• Step 6: Post-Centrifugation Handling

After centrifugation, carefully remove the tube from the rotor without disturbing the pellet or layers.

Depending on the experiment, either the supernatant (liquid phase) or pellet (solid phase) should be carefully collected using a pipette. Avoid resuspension unless required by the protocol.

Proper handling at this stage ensures sample integrity and improves downstream experimental accuracy.

Common Mistakes When Using Centrifuge Tubes

Incorrect use of centrifuge tubes can lead to sample loss, experimental failure, equipment damage, and even safety risks. Understanding common mistakes helps improve laboratory efficiency and ensures reliable results.

• Overfilling tubes beyond maximum capacity

One of the most common mistakes is filling centrifuge tubes beyond their recommended maximum volume.

Overfilling increases the risk of leakage during centrifugation, especially at high speeds. It may also cause imbalance in the rotor and reduce separation efficiency.

To avoid this, always leave sufficient headspace in the tube according to manufacturer guidelines.

• Improper balancing of tubes

Failing to properly balance centrifuge tubes is a critical error that can cause serious instrument damage.

Even small differences in mass can result in strong vibration, rotor wear, or centrifuge malfunction. In severe cases, it may lead to equipment failure or safety hazards.

Always balance tubes by weight, not by volume, especially in high-speed or sensitive experiments.

• Using low-grade tubes for high-speed centrifugation 

Not all centrifuge tubes are designed for high-speed or ultracentrifugation applications.

Using low-quality or low-RCF-rated tubes under high centrifugal force can result in cracking, deformation, or leakage. This not only compromises experimental results but may also damage the centrifuge rotor.

Always select tubes with verified RCF ratings that match your experimental conditions.

• Reusing disposable tubes

Disposable centrifuge tubes are designed for single use only.

Reusing them may lead to contamination, reduced mechanical strength, and unpredictable performance under centrifugal force. This is particularly dangerous in molecular biology, clinical, and sterile applications.

For reliable results and biosafety, always use fresh tubes for each experiment.

• Incomplete sealing causing leakage

Improper or incomplete sealing of centrifuge tube caps can result in leakage during centrifugation.

This may lead to sample loss, contamination, or aerosol formation, which can pose biosafety risks in biological or clinical laboratories.

Always ensure that caps are fully tightened and properly aligned before starting centrifugation.

Top Questions About Centrifuge Tubes Answered

How full should the centrifuge tube be?

The filling volume of a centrifuge tube is an important factor that directly affects centrifugation safety and experimental performance. Filling the tube with too little or too much sample can increase the risk of imbalance, sample loss, or tube failure. As a general guideline, the sample volume should be maintained between one-third (1/3) and three-quarters (3/4) of the tube’s total capacity, unless otherwise specified by the tube manufacturer or experimental protocol.

Minimum Filling Volume: At Least One-Third Full

A centrifuge tube should generally contain at least one-third of its total capacity. If the sample volume is too low, the tube may become unstable during centrifugation, particularly when using high-speed centrifuges. In addition, extremely small sample volumes make it more difficult to balance opposing tubes accurately.

Benefits of maintaining the minimum filling volume:

• Provides sufficient mass for accurate balancing.
• Improves tube stability during centrifugation.
• Reduces vibration and unnecessary stress on the rotor.

Maximum Filling Volume: No More Than Three-Quarters Full

To ensure safe operation, centrifuge tubes should not be filled beyond approximately 75% of their total capacity. During centrifugation, especially at high speeds, samples expand and generate internal pressure. Leaving adequate headspace helps prevent leakage and reduces stress on the tube and cap.

Benefits of leaving headspace:

• Prevents liquid from leaking through the cap.
• Reduces the risk of the lid opening unexpectedly.
• Minimizes tube deformation under high centrifugal force.
• Helps maintain sample integrity.

Why must the new tube be centrifuged?

Why Should Centrifuge Tubes Be Briefly Spun Down Before Use?  Brief centrifugation, often referred to as “spin-down,” is a common laboratory practice used before or after adding samples into centrifuge tubes. Although it may seem like a minor step, it plays an important role in improving accuracy, preventing sample loss, and ensuring consistent experimental results.

• To Collect Liquid at the Bottom of the Tube

During pipetting or sample preparation, small droplets of liquid may remain on the tube walls or inside the cap. Brief centrifugation helps bring all liquid down to the bottom of the tube.

• To Improve Mixing of Samples

In many experiments, reagents may not be fully mixed after pipetting. A short spin helps combine all components uniformly at the bottom of the tube.

• To Reduce Air Bubbles and Surface Tension Effects

Liquid droplets trapped in the tube cap or along the walls may contain air bubbles or be affected by surface tension. Brief centrifugation helps eliminate these issues.

• To Improve Experimental Reproducibility

Even small variations in sample distribution can affect experimental outcomes, especially in molecular biology and PCR applications. Spin-down ensures that all samples start from a consistent state.

Can Centrifuge Tubes Be Cleaned? Are They Single-Use?

Can centrifuge tubes be cleaned and reused, or are they strictly single-use consumables? In some cases, is it possible to clean centrifuge tubes, and if so, how to clean centrifuge tubes?

Are Centrifuge Tubes Single-Use?

In most laboratory workflows, centrifuge tubes made of polypropylene (PP) are intended for single use only. Reasons include: Risk of cross-contamination; Loss of sterility after opening; Reduced mechanical strength after centrifugation; Chemical residue retention. 

Therefore, in PCR, DNA/RNA extraction, and cell culture experiments, reuse is strictly not recommended.

Can Centrifuge Tubes Be Cleaned and Reused?

Can Centrifuge Tubes Be Cleaned and Reused? Suitable conditions for reuse: Non-sterile experiments; Non-biological samples; Low-speed centrifugation; Short-term use only.

Proper Cleaning Method for Centrifuge Tubes

If reuse is necessary, the following cleaning procedure should be followed:

• Immediate rinsing. Rinse the tube with distilled or deionized water immediately after use to prevent residue drying.

• Detergent washing. Wash using mild laboratory detergent to remove residues.

• Thorough rinsing. Rinse several times with distilled water to remove any detergent residues.

• Drying. Air-dry completely in a clean environment before reuse.

Centrifuge tubes are primarily designed as single-use consumables to ensure accuracy, sterility, and safety in laboratory workflows. However, in limited non-critical applications, they may be cleaned and reused using proper washing procedures, although this is generally not recommended for sensitive experiments.

How To Balance 5 Tubes in a Centrifuge?

When the number of test tubes required to centrifuge is 5, balancing these test tubes correctly is key to ensuring the safe operation of the centrifuge. Centrifuges rely on extreme weight distribution to maintain operational stability, and an odd number of test tubes (such as 5) cannot be formed naturally, and some additional measures must be taken to achieve balance.

The most common practice is to add a “balance tube” to make the total number of test tubes 6. You can use a centrifuge tube of the same model as the other 5 test tubes, insert an equal volume and weight (usually liquid or buffer), and use it as the sixth tube. This tube does not participate in the experiment, it is only balanced.

When placing the plastic centrifuge tubes, the six tubes should be placed evenly and symmetrically in the rotor. For example, after placing the first tube in a slot, place the fourth tube opposite; the fifth tube opposite the second tube; and the sixth tube opposite the third tube (balance tube). This will form three symmetrical pairs of tubes to ensure that there is no bias during centrifugation.

If it is really impossible to add additional tubes, you can also consider using a professional symmetrical arrangement, such as staggering the test tubes in some models of multi-hole rotors and trying to form a nearly balanced structure. However, this method is risky and is only recommended for experienced personnel who have a full understanding of the load allowed by the centrifuge.

In addition, some high-end centrifuges are equipped with an automatic balancing function that can automatically adapt to slightly asymmetrical loads. However, for most laboratory centrifuges, it is still recommended to manually balance the weight accurately, and use a balance to weigh each tube when necessary to ensure that the error is controlled within ±0.1 grams.

In short, the correct way to do it when there are 5 graduated centrifuge tubes is to add a matching balance tube to make it an even number, and then place them symmetrically. Never put 5 tubes directly into the centrifuge asymmetrically to avoid damage to the machine or loss of samples.

Summary

Proper use of centrifuge tubes is essential for ensuring safe, accurate, and reproducible laboratory results. It involves selecting the appropriate tube type, controlling the correct filling volume, properly balancing tubes before centrifugation, and following recommended speed and safety limits. Avoiding common mistakes such as overfilling, improper sealing, or using unsuitable tubes for high-speed applications helps prevent sample loss, contamination, and equipment damage. Overall, standardized handling of centrifuge tubes is a simple but critical step in improving experimental efficiency and data reliability.