How to Choose the Right Centrifuge Tubes? Complete Selection Guide

A Variety of Centrifuge Tubes: How to Choose?

Previous discussions covered the working principles and operating procedures of centrifuges (including the mechanism,centrifugal force conversion, and rotor selection), as well as precautions and rapid balancing techniques during centrifugation. Today, we will explore the materials used for centrifuge tubes and how to select the right tube for your experiment.

I. Classification of Centrifuge Tubes

(1) Classification by size:

Large-capacity centrifuge tubes: 500 mL, 250 mL; suitable for processing large-volume samples.

Standard centrifuge tubes: 50 mL, 15 mL; meet the majority of routine experimental needs.

Micro-centrifuge tubes: 2 mL, 1.5 mL, 0.65 mL, 0.2 mL; the preferred choice for processing micro-volume samples.

(2) Classification by bottom shape:

Conical-bottom centrifuge tubes: Feature a conical bottom design that facilitates the separation of sample pellets; they offer stable rotation and are widely used. They are suitable for low-speed centrifugation in benchtop centrifuges; the pellet concentrates more easily at the bottom, especially during horizontal (swing-out) centrifugation. However, during fixed-angle or high-speed centrifugation, the pointed bottom design may generate localized stress, potentially causing the tube to crack; generally, a centrifugal force not exceeding 10,000 x g is recommended.

Flat-bottom centrifuge tubes: Their usage is similar to that of conical tubes, but the design allows them to stand upright on their own, making experimental handling and placement more convenient.

Round-bottom centrifuge tubes: These feature a larger bottom surface area, allowing them to withstand higher centrifugal forces. They also ensure more uniform heating of the tube body during centrifugation, yielding superior results. Consequently, they are generally suitable for high-speed or even ultracentrifugation experiments. Round-bottom tubes are also used for density gradient collection.

(3) Classification by closure method

Snap-cap centrifuge tubes: Sealed by pressing the cap down; commonly found in micro-centrifuge tubes and easy to operate.

Screw-cap centrifuge tubes: Available in flat-cap and plug-seal cap styles; they provide a tight seal and are suitable for long-term sample storage or transport.

(4) Classification by material

Plastic centrifuge tubes: Transparent or translucent, lightweight, and durable; commonly used in laboratories.

Glass centrifuge tubes: Offer good chemical corrosion resistance and high-temperature stability; preferred for specific types of experiments.

Steel centrifuge tubes: High strength, resistant to deformation, heat, freezing, and chemical corrosion; utilized in specialized experimental environments.

II. Plastic centrifuge tubes

Plastic centrifuge tubes are made from materials such as PP (polypropylene), PC (polycarbonate), and PE (polyethylene).

(1) PP (Polypropylene)

Polypropylene (abbreviated as PP) is a polymer produced through the addition polymerization of propylene.

Characteristics:

Withstands high-temperature disinfection; can undergo autoclaving at 121°C.

Chemically stable and translucent; suitable for experiments requiring resistance to chemical reagents, such as DNA/RNA extraction.

Possesses moderate rigidity; suitable for high-speed centrifugation.

Disadvantages:

Due to the presence of numerous tertiary carbon atoms with methyl groups along the PP backbone—where the hydrogen atoms on these tertiary carbons are susceptible to oxidative attack—PP exhibits poor weather and aging resistance and tends to degrade under the influence of oxygen and ultraviolet (UV) light.

Becomes brittle at low temperatures.

(2) PC (Polycarbonate)

Polycarbonate, also known as PC plastic, is a polymer containing carbonate groups (-O-C(=O)-O-) in its molecular chain.

Characteristics:

It offers good transparency and high mechanical strength; it is primarily used for ultra-high-speed centrifugation exceeding 50,000 rpm, such as in virus isolation and subcellular organelle extraction.

It has good high-temperature resistance: it can withstand autoclaving at 121°C and sterilization in an autoclave.

Disadvantages:

It is not resistant to strong bases; specifically, exposure to substances like sodium hydroxide or aqueous ammonia can easily trigger hydrolysis, leading to molecular chain breakage and a decline in mechanical properties. It is also sensitive to nuclease inhibitors such as diethyl pyrocarbonate (DEPC).

It is a brittle material; cracks may appear after as few as one or two uses in an ultracentrifuge, so it must be carefully inspected for cracks before use.

It has a relatively high cost.

(3) PE (Polyethylene)

Polyethylene (PE) is a thermoplastic resin produced through the polymerization of ethylene monomers.

Characteristics:

It exhibits good chemical stability; because the polymer molecules are linked by carbon-carbon single bonds, it resists corrosion by most acids and alkalis (though not oxidizing acids) and does not react with substances such as acetone, acetic acid, or hydrochloric acid.

It has good low-temperature resistance; the brittleness temperature is generally below -50°C. As the relative molecular mass increases, this minimum temperature can drop to -140°C or even the -196°C level of liquid nitrogen.

It has relatively low transparency and is primarily used for low-speed centrifugation and low-temperature sample storage, such as cell cryopreservation.

Disadvantages:

Polyethylene has poor heat resistance and tends to soften at high temperatures.

It is prone to degradation under ultraviolet (UV) light, although carbon black provides excellent light-shielding properties. Exposure to radiation can also trigger reactions such as cross-linking, chain scission, and the formation of unsaturated groups.

Polyethylene is insoluble in common solvents at temperatures below 60°C, but prolonged contact with aliphatic hydrocarbons, aromatic hydrocarbons, or halogenated hydrocarbons can cause swelling or cracking.

(4) PS (Polystyrene)

Polystyrene (abbreviated as PS) is a polymer synthesized from styrene monomers via free-radical addition polymerization; its chemical formula is (C8H8)n.

Features: High transparency, making it easy to observe the state of the sample.

Disadvantages:

High rigidity; stable in most aqueous solutions but susceptible to corrosion by various organic substances; primarily used for low-speed centrifugation; generally intended for single use.

III. Glass Centrifuge Tubes

Features:

Chemical resistance: Highly resistant to various chemical reagents; suitable for diverse chemical experimental environments.

High-temperature stability: Can withstand high-temperature drying and autoclaving; suitable for experiments conducted at high temperatures.

High transparency: Easy to observe contents.

Reusable: Glass is relatively easy to clean and convenient for repeated use.

Disadvantages:

Brittleness: Must be protected from external impact or crushing forces during use.

Centrifugal force limitations: Centrifugal force should not be excessive; rubber cushions are required to prevent breakage; generally not selected for high-speed centrifuges.

Due to their fragility, the strength of glass tubes varies depending on the glass composition. Ordinary soda-lime glass cannot withstand relative centrifugal forces (RCF) exceeding 3,000g, whereas borosilicate glass (such as Corex glass) can withstand RCFs exceeding 10,000g. These are primarily used for centrifugation operations requiring exceptional transparency or high-temperature processing, such as centrifuging radioisotope-labeled samples or monitoring chemical reactions at high temperatures.

IV. Steel Centrifuge Tubes

Features:

High strength: Can withstand significant external force; resistant to deformation.

Heat and cold resistance: Stable performance in both high- and low-temperature environments.

Chemical corrosion resistance: Resistant to corrosion by various chemical substances.

Disadvantages:

Risk of chemical corrosion: Must avoid contact with highly corrosive chemicals, such as strong acids or strong bases, during use.

V. How to Choose Centrifuge Tubes

1. Centrifugal Force

Select a centrifuge tube made of a suitable material based on the required centrifugation speed. For low-speed centrifugation (below 10,000 rpm), tubes made of PE or PS are suitable; for medium-to-high speeds (10,000–20,000 rpm), PP tubes are appropriate; for high-speed centrifugation (above 20,000 rpm), PC or metal tubes should be used to ensure they do not rupture during high-speed rotation.

2. Temperature Tolerance

If the experiment requires low-temperature refrigerated centrifugation, choose materials resistant to low temperatures, such as PE or PC. For high-temperature processing, glass or PC tubes are preferable, although PP tubes can also withstand certain high temperatures.

3. Centrifuge Compatibility

Ensure the selected centrifuge tube is compatible with the centrifuge rotor to avoid experimental failure caused by mismatches.

A proper fit between the centrifuge tube and the centrifuge sleeve is crucial, especially under high centrifugal forces; if the tube is too small, it may not fit snugly against the sleeve, potentially leading to leakage or even breakage.

4. Physical properties

5. Chemical Compatibility

(1) Chemical Composition: Consider the chemical composition and corrosiveness of the sample. For samples containing strong acids, strong bases, or organic solvents, select materials with good chemical resistance, such as PP or glass. For example, when handling organic solvents like phenol or chloroform, avoid using PS (polystyrene) centrifuge tubes, as PS is easily dissolved by organic solvents; conversely, glass centrifuge tubes are a safer choice when handling highly corrosive samples such as concentrated hydrochloric acid or sodium hydroxide.

(2) Corrosiveness: For corrosive samples, in addition to the material's chemical resistance, consider the tube's surface treatment; some plastic centrifuge tubes feature surface coatings that enhance corrosion resistance.

6. Sample Viscosity

Sample viscosity affects centrifugation performance. For highly viscous samples, low-retention tubes can be used to minimize sample residue and improve centrifugation efficiency.

Low-retention centrifuge tubes are typically manufactured using polymer surface treatment technologies—such as the application of long-chain alkyl groups, hydrophobic groups, or silane groups—to modify the surface. This treatment reduces surface affinity, thereby minimizing contact between the sample and the tube wall during centrifugation, reducing sample retention on the inner wall, minimizing sample loss, and ensuring sample purity and accuracy.

Low-retention centrifuge tubes are used in the same way as standard centrifuge tubes, though operating conditions differ. Avoid using them at extreme high or low temperatures to preserve their specific surface properties.

7. Experimental Requirements

(1) Transparency: If the experiment requires monitoring the sample's state, choose materials with high transparency, such as PS, PC, or glass.

(2) Sealing: For toxic or radioactive samples, select centrifuge tubes with excellent sealing capabilities. Most plastic centrifuge tubes feature sealing caps that effectively prevent leakage; while glass centrifuge tubes may have sealing mechanisms, their sealing performance is generally inferior, so they are not recommended for these applications.

(3) Capacity: Select a centrifuge tube with an appropriate capacity based on the sample volume.