P20 Pipette: Which Volume Range Suits Small-Volume Laboratory Work?
At 20 µL, a slip of half a microlitre is 2.5 per cent of the transfer. At 2 µL, the same slip is 25 per cent. A P20 pipette lives at the error-amplifying end of the bench, which is why the volume range it is ordered for matters more than the brand on the side.
Small-volume work is where a pipette stops being a convenience and becomes part of the measurement. The questions to settle before ordering are the range the method needs, the tip the instrument seals against, and the record the laboratory is expected to keep.
What does a P20 pipette measure?
The number in a micropipette name is its maximum volume. A P20 aspirates up to 20 µL, and its usable range is normally 2 to 20 µL. The family runs in steps, each named for its ceiling: P2, P20, P200 and P1000. A laboratory orders a P20 for the 2 to 20 µL band, not as a general-purpose instrument, because the specified accuracy of any micropipette sits inside a fraction of its maximum.
Which volume belongs on a P20, and which does not?
The smaller the volume, the more a fixed slip costs in percentage terms. That is the whole argument for matching the instrument to the transfer.
| Nominal volume | A slip of 0.5 µL is | How it reads |
|---|---|---|
| 2 µL | 25 per cent | enough to break a sensitive reaction |
| 5 µL | 10 per cent | marginal for quantitative work |
| 10 µL | 5 per cent | acceptable for most assays |
| 20 µL | 2.5 per cent | comfortable and repeatable |
The same half microlitre that is harmless at 20 µL is a quarter of the volume at 2 µL, which is why a low-volume bench treats tip fit and technique as part of the result.
Which tip fits a P20?
A P20 takes the small tip, commonly a 10 or 200 µL tip, and most suppliers colour it yellow. The colour is a supplier convention rather than a regulated code, so the useful check is fit, not colour. A tip that does not seal on the cone leaks air, and an air leak is the most common reason a pipette under-delivers. Confirm the tip the supplier specifies for the model before committing to a case, because a tip sized for one brand's cone may not seal on another.
How much error is acceptable at low volume?
ISO 8655 is the standard that covers piston-operated volumetric apparatus, the family a micropipette belongs to. It sets out how accuracy and repeatability are tested, and testing runs at more than one test volume, including a low one near the bottom of the range, rather than only at the maximum. A supplier that quotes a single figure at 20 µL has told you nothing about the 2 µL transfer the method depends on, so ask for the results at the volumes the bench actually uses.
When should a lab use a P20 instead of a P200?
When the transfer is at or above 20 µL, the P200 is the right instrument, because a P200 covers 20 to 200 µL and keeps the transfer inside a specified range. The P20 earns its place below 20 µL, where a P200 is too coarse to resolve the volume. A small-volume bench usually keeps both, and a P1000 for the media and buffer that feed the reagents.
What does ISO 15189 expect of a Canadian laboratory?
A Canadian medical laboratory accredited to ISO 15189 is expected to keep measuring equipment under control, and for a P20 that means a calibration or verification record on a defined interval. The record names the instrument, the date and the result, and notes the action taken when a result falls outside tolerance. On a low-volume bench that record is also the simplest defence when a result is questioned.
Ordering for a clinic, lab or care home? Wholesale and multi-site ordering covers case pricing and account setup, and the B2B wholesale collection lists the lines stocked for institutional buyers.
A small-volume bench restocks 15 mL centrifuge tubes for dilutions, 100 × 15 mm petri dishes for plating, and graduated 90 mL specimen cups for sample handling, all listed under laboratory consumables.
References
- ISO 8655-1:2022 — Piston-operated volumetric apparatus, Part 1: terminology and general requirements (checked 29 September 2026)
- ISO 8655 — pipette calibration and verification, Sartorius (checked 29 September 2026)
- ISO 15189:2022 — Medical laboratories, requirements for quality and competence (checked 29 September 2026)
- Improvement of the pour plate method, PMC9927588 (checked 29 September 2026)
Related Reading
- Centrifuge Tube Volume Graduations: What Do the Marks Actually Mean?
- Microcentrifuge Tubes in Canada vs the US: Which Standards and Labelling Apply?
- Lab Equipment in Canada vs the US: Which Licensing Route Applies?
Frequently Asked Questions
What volume does a P20 pipette hold?
Up to 20 µL, and its usable range is normally 2 to 20 µL. The name states the maximum, so a 1 µL transfer belongs on a smaller instrument rather than at the bottom of a P20.
Which tips fit a P20 pipette?
A 10 or 200 µL tip, usually colour-coded yellow. Tip fit protects accuracy, so confirm the tip the supplier specifies for the model rather than assuming any yellow tip seals on the cone.
How accurate is a P20 pipette at 2 µL?
Accuracy is stated as a percentage of the volume, so the smallest volume in the range carries the largest relative error. A fixed slip of half a microlitre is 25 per cent at 2 µL and only 2.5 per cent at 20 µL.
When should a lab use a P200 instead of a P20?
When the transfer is above 20 µL. A P200 covers 20 to 200 µL, so a 50 µL or 100 µL transfer stays inside a specified range instead of pushing a P20 past its maximum.
Do P20 pipettes need calibration records in Canada?
A laboratory accredited to ISO 15189 is expected to keep measuring equipment under control, which for a P20 means a calibration or verification record on a defined interval, with the result kept for an assessor.
Last updated: September 2026. CliniEco Medical is a licensed medical device establishment (MDEL #35334).
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