A postdoc I know once spun a 15 mL conical tube at 12,000 × g because “the rotor fits, so it’s fine.” The tube flattened into a plastic pancake, the sample aerosolized inside the bucket, and the cleanup took the rest of the afternoon. Centrifuge tubes look interchangeable. They are not, and the two things that make them different are material and volume rating.
Centrifuge tubes are typically made of polypropylene (PP), polypropylene copolymer (PPCO), polycarbonate (PC), polyallomer, or glass, and each material carries a maximum relative centrifugal force (RCF) rating plus its own chemical tolerance. Volume ratings run from 0.5 mL micro tubes to 250 mL+ bottles, and the rating printed on the tube assumes you stay within its RCF limit.
Here’s how to choose without learning the hard way.
The Materials, One at a Time
• Polypropylene (PP). The default. Good chemical resistance, tolerates most aqueous buffers, salts, and many organics poorly to moderately. Autoclavable, cheap, and rated to roughly 15,000 to 20,000 × g in standard formats. If you only remember one material, remember this one.
• Polypropylene copolymer (PPCO). Clearer than standard PP and a bit more impact-resistant at low temperature. Common in 15 and 50 mL conical tubes. Same solvent caveats as PP: strong aromatics and chlorinated solvents will attack it over time.
• Polycarbonate (PC). Glass-clear and rigid, with high RCF ratings, which is why ultracentrifuge bottles often use it. But PC cracks with certain solvents, doesn’t love repeated autoclaving, and is the tube I’ve seen shatter most often in an angle rotor. Handle accordingly.
• Polyallomer. A copolymer blend used in ultracentrifuge tubes. Good for density gradient work because it’s smooth and doesn’t bind samples aggressively.
• Glass. Still relevant for solvent-heavy applications where plastics swell, and for some cell sedimentation work. My general take on glass versus plastic for labware is the same as for bottles, which I covered in the glass vs plastic labware comparison: glass for harsh chemistry and reuse, plastic for convenience and safety.
Solvent compatibility deserves one more sentence. If your sample contains chloroform, toluene, or concentrated acids, check a compatibility table before the spin, not after. Published work on plastics extractables shows even “compatible” plastics leach low-level compounds into aggressive solvents, which matters for sensitive LC-MS work.
Regulated labs should also think about what the tube contributes to the record. Under 21 CFR 211.65, contact surfaces must not be reactive, additive, or absorptive to the product, and a centrifuge tube is a contact surface in every sense. Vendor material guidance is worth keeping on file; this centrifuge tube material guide is a useful one-page reference for PP, PPCO, and glass options.
What the Volume Rating Actually Means
The mL printed on a tube is its nominal capacity, not its promise at speed. Two numbers matter:
1. Fill volume limits. Many tubes specify a maximum fill below the rim, especially at high RCF, because liquid pressure deforms the tube wall. Exceeding it causes leaks at the cap or deformation that shifts the balance.
2. RCF rating. This is the real rating, printed as × g. A tube that tolerates 20,000 × g when filled to 80% may not tolerate it full. When in doubt, underfill and cap properly.
A quick reality check I do before a new spin: multiply the rotor’s max RCF by the fraction of the tube I’ve filled. If my intended g-force is within the rating at my fill level, proceed. If it’s marginal, use a bigger tube or a slower spin. Fixed-angle rotors concentrate force on the tube wall at one spot, which is why angle-rotor failures are more dramatic than swinging-bucket ones.
Reading the Rotor’s Side of the Contract
Tube ratings only matter relative to the rotor. The same tube at the same RPM produces very different g-forces in a swinging bucket versus a fixed angle head, and rotor specs list the maximum speed per tube type. Modern centrifuges often ask you to confirm the tube type at setup and will enforce the limit; older machines trust you entirely.
Two rotor-side habits worth building: check the rotor’s O-rings and lubrication during monthly maintenance, because a corroded bucket deforms tubes, and balance by mass, not by eye. Two tubes that “look even” but differ by half a gram will walk a bearing loose over a month of spins.
Adapters deserve a warning of their own. A 15 mL tube in a 50 mL adapter sits differently than it does in its own bucket, and the effective g-force at the tube wall changes with the geometry. If your lab uses adapters, confirm the rated combination in the rotor manual rather than assuming the lower tube’s rating carries over.
Matching Tube to Task
• Routine pelleting, spins under 5,000 × g: standard PP conicals, 15 or 50 mL.
• Protein or nucleic acid prep, 10,000 to 20,000 × g: 1.5 and 2 mL PP micro tubes, check the brand’s g rating; not all 2 mL tubes hit 20,000.
• Density gradients and ultracentrifugation: polyallomer or PC ultracentrifuge tubes, absolutely within the rotor’s speed limits for that tube type.
• Solvent extracts: glass tubes or solvent-resistant PP, verified against the solvent.
• Frozen storage after spinning: PP again, and note that freeze-thaw cycles shorten tube life; my cryogenic storage guide covers cold-storage formats.
If your work is molecular biology rather than solvent chemistry, material choice gets one more filter: DNase- and RNase-free certification, which I unpacked in the DNase/RNase-free consumables explainer.
Conclusion
Centrifuge tubes differ in two ways that matter: the polymer they’re made of and the RCF they’re rated to survive at a given fill volume. Polypropylene covers most everyday work, polycarbonate and polyallomer serve the high-force end, and glass earns its keep with aggressive solvents. Check the × g rating against your rotor at your actual fill level, respect the fill line, and never assume that a tube fitting in the rotor means it can take the speed. Keep a small compatibility cheat sheet near the centrifuge, and when a new solvent or an unusually fast spin comes up, look it up first. The minute of checking is much cheaper than the aerosol cleanup. If you’re building out your tube and vial inventory, start with the formats you run weekly and add specialty tubes only when a method demands them.
Frequently Asked Questions
Can I autoclave polypropylene centrifuge tubes?
Most PP and PPCO tubes are autoclavable at 121°C, but check the manufacturer’s mark, because repeated cycles embrittle them and caps often have lower temperature ratings. My autoclaving consumables guide covers the general rules.
What does RCF mean on a centrifuge tube?
RCF, relative centrifugal force, is the g-force the tube experiences, and it’s what ratings are based on. Convert from RPM using your rotor’s specifications, since the same RPM produces different RCF in different rotors.
Why did my tube crack in the centrifuge?
Common causes: exceeding the RCF rating, overfilling, solvent incompatibility, autoclave-weakened plastic, or a fixed-angle rotor concentrating force at the wall. Polycarbonate is the most crack-prone of the common materials.
Are all 50 mL conical tubes the same?
No. Wall thickness, cap design, and RCF ratings vary between brands, and sterile, DNase-free, or low-retention versions differ in price and performance. Match the specification to your spin, not just the size.
