Pasteur Pipettes vs Serological Pipettes: What Actually Differs

The two are often stored in the same drawer and confused in the same sentence, but they are different instruments. A Pasteur pipette transfers liquid; a serological pipette measures it. That single difference decides which one belongs in a protocol, and using one in place of the other is the source of a surprising number of failed dilutions.

The short answer

A Pasteur pipette has no graduations. Volume is estimated by eye and experience, and the error on a transferred volume typically exceeds 30 per cent. A serological pipette (often sold as a “serum pipette”) carries moulded bidirectional graduations and is calibrated to within about ±1 to ±2 per cent, which makes it a measuring instrument rather than a transfer tool.

Accuracy, plainly stated

	Pasteur pipette	Serological pipette
Graduations	None	Moulded, bidirectional, colour-coded by volume range
Typical error	Estimated; over 30 per cent	±1 to ±2 per cent as calibrated
Fit for quantitative work	No	Yes, within its stated tolerance

Note what “±1 to ±2 per cent” means in practice: at 10 mL, a 2 per cent error is 200 µL. That is acceptable for preparing buffer and unacceptable for a standard curve. Calibrated does not mean exact.

Construction and how the liquid moves

Pasteur pipette. Blow-moulded in one piece from polyethylene, so the whole tube is flexible. You squeeze the bulb or the tube itself to create the vacuum, and the liquid follows. There is no separate bulb to lose and no filter plug at the tip. The design is cheap, robust and completely non-quantitative.

Serological pipette. Made from rigid polystyrene (GPPS), which cannot be squeezed. It is used with a manual pipette pump or an electric pipettor, and the seal at the top is what makes aspiration controllable. Because the body is rigid and straight, the graduations can be moulded accurately along its length.

The filter plug is not a minor detail

Good serological pipettes carry a hydrophobic polyester or sintered polyethylene plug near the top. It passes air, blocks aerosols and stops liquid from reaching the pipettor. Without it, a single over-aspiration pulls medium into the pump body, and every subsequent use of that pump is a contamination risk. On a shared instrument used by six people, that is how a culture room gets an infection it cannot trace.

Where each one belongs

Task	Correct tool	Why
Removing spent medium before a wash	Pasteur	Volume is irrelevant; speed and reach matter
Loading an agarose gel	Pasteur (fine tip)	Needs a narrow tip and a steady squeeze, not a measurement
Adding a few drops of reagent	Pasteur	Approximate by design
Aliquoting medium into flasks	Serological	Each flask needs the same volume
Gradient dilution of a cell suspension	Serological	The dilution factor depends on an accurate transfer
Dispensing serum or supplement into medium	Serological	Small volumes of expensive reagent, sterile handling

Bulk versus individually wrapped

Pasteur pipettes are usually supplied in bulk bags of 500, in 1 mL, 3 mL and 5 mL sizes, non-sterile by default. They are cheap enough to be treated as disposable transfer tools.

Serological pipettes come individually wrapped and gamma sterilised when they are intended for cell work, in a range from 1 mL to 50 mL. The packaging is part of the product: an individually wrapped pipette can be opened inside a clean bench without the outer surface contaminating the tip.

Two habits worth fixing

• Using a Pasteur pipette to “measure” a small volume. The tip geometry makes drops inconsistent, and the error compounds across a dilution series.
• Using a serological pipette to remove waste liquid. You pay for calibration and sterility on every unit, then use it as a spatula. Keep a bag of Pasteur pipettes next to the aspirator.

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Note: The information on the scientific research products above is for reference only!