Pipetting is often treated as a purely mechanical task.
Set the volume, attach the tip, aspirate, and dispense.
But in reality, temperature plays a much larger role than many researchers realize.
Even a difference of just 5°C between your pipette, the surrounding air, and the liquid being handled can introduce measurable errors in liquid handling.
If you’ve ever wondered why pipetting seems less reliable when working with cold reagents or samples taken directly from a refrigerator, temperature is often the hidden factor.
Let’s explore why.
Air-Displacement Pipettes Depend on Temperature
Most laboratory pipettes are air-displacement pipettes.
Inside the pipette, a small air cushion separates the piston from the liquid sample.
When you aspirate liquid, this air cushion expands and contracts to move the liquid.
However, air is highly sensitive to temperature.
When temperature changes:
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Warm air expands
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Cold air contracts
This physical behavior directly affects the volume of liquid aspirated and dispensed.
Because of this, air-displacement pipettes are most accurate when the pipette, the liquid, and the surrounding air are all at similar temperatures.
What Happens When Liquids Are Colder Than the Pipette?
One common situation is pipetting liquids taken directly from a 4°C refrigerator.
When cold liquid is aspirated:
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The air cushion inside the pipette cools rapidly.
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Cooling causes the air to contract.
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This contraction reduces the pressure inside the tip.
The result?
More liquid may be drawn into the tip than intended.
This can lead to over-aspiration and inconsistent dispensing, especially when working with small volumes.
What Happens When Liquids Are Warmer?
The opposite can also occur.
If the liquid is warmer than the pipette:
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The air cushion expands
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Internal pressure increases
In this case, less liquid may be aspirated than expected, leading to under-delivery.
While the difference may appear small, at micro-liter volumes even tiny deviations can impact experimental reproducibility.
Why Small Temperature Differences Matter More at Low Volumes
Temperature effects become more noticeable when working with small volumes.
For example:
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At 200 µL, a slight variation may be negligible.
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At 2 µL, the same physical effect becomes proportionally much larger.
This is why low-volume pipetting often feels less stable, even when the pipette is calibrated.
Practical Tips to Reduce Temperature Effects
Fortunately, temperature-related errors can often be minimized with simple precautions.
Allow reagents to equilibrate
Whenever possible, allow liquids to reach room temperature before pipetting.
Pre-wet the pipette tip
Aspirating and dispensing the liquid once or twice before the actual measurement helps stabilize the temperature inside the tip.
Work quickly but consistently
Holding a pipette in your hand for long periods can warm the internal air cushion.
Avoid large temperature gradients
Ideally, the pipette, tips, liquid, and environment should all be within a few degrees of each other.
Temperature Control Improves Reproducibility
Temperature is rarely the first thing researchers consider when troubleshooting pipetting errors.
However, when working with sensitive assays such as:
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PCR preparation
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enzyme reactions
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low-volume sample handling
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high-precision quantitative work
temperature differences can have a measurable impact.
By simply paying attention to temperature equilibrium, many labs can significantly improve pipetting consistency.
Final Thoughts
Pipetting accuracy isn’t determined only by calibration.
It also depends on the interaction between:
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the pipette
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the liquid
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the surrounding air
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and the temperature of each.
Even a 5°C difference can influence liquid handling behavior.
Understanding this small but important factor can help reduce variability and improve experimental reproducibility.
Sometimes, the difference between inconsistent data and reliable results is just a few degrees.