Pipette tips are disposable consumables used in large quantities during everyday laboratory work.
Because of this, deciding exactly when a tip should be replaced may seem simple, but in practice it can be surprisingly unclear.
For example:
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Can the same tip be used repeatedly with the same reagent?
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Do you need to change the tip if you are working with the same sample?
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What about dispensing into multiple wells?
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Can filter tips be used longer than standard tips?
The purpose of changing a pipette tip is not simply to follow a rule that says, “Always use a new one.”
The main reasons are to reduce cross-contamination, prevent carryover between samples or reagents, and keep pipetting conditions as consistent as possible.
In this article, we explain common situations in which pipette tips should be replaced and the key points to consider when deciding whether a tip can continue to be used.
Why Do Pipette Tips Need to Be Replaced?
There are three main reasons to change a pipette tip:
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To reduce cross-contamination between samples
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To prevent carryover of reagents or solutions
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To maintain more consistent dispensing conditions
Even when a pipette tip looks clean, a small amount of liquid may remain inside the tip or around its opening.
This means that a previous sample or reagent may be transferred into the next one even when no visible liquid remains.
This is particularly important in workflows such as PCR, DNA or RNA handling, and cell culture, where even a small amount of contamination can affect results.
For contamination-sensitive work, clear tip-changing rules should be established in advance.
Change the Tip When the Sample Changes
As a general rule, a new tip should be used when moving from one sample to another.
Even if the samples are the same type, switching to a different sample creates a risk that material from the previous sample may be carried over.
For example, if you pipette in the following order:
Sample A → Sample B → Sample C
and continue using the same tip, a small amount of Sample A may be transferred into Sample B, and material from Sample B may then be carried into Sample C.
In sensitive analytical workflows, even a small amount of carryover can affect the result.
The important question is not whether the liquids are the same type, but whether the sample itself has changed.
Change the Tip When the Reagent Changes
A new tip should also be used when switching from one reagent to another, even if you are working with the same sample.
For example, when several reagents are added sequentially to the same tube, residual liquid inside the tip may be transferred into the next reagent stock.
Contamination is not limited to sample-to-sample transfer.
Reagent-to-reagent contamination should also be considered.
This is especially important in laboratories where the same reagent bottles are shared by multiple users.
A small amount of contamination introduced into a shared stock solution may affect many later experiments.
When aspirating from a reagent stock, using a clean tip is the safest basic practice.
What About Dispensing the Same Reagent Into Multiple Wells?
When the same reagent is aspirated from the same source and dispensed into multiple wells or tubes, the same tip may sometimes be used repeatedly depending on the experimental conditions.
The key question is not how many times the tip has been used.
It is what the tip has touched.
For example, when dispensing the same reagent across a 96-well plate, the tip may be reused as long as it remains uncontaminated.
However, if the tip touches liquid already present in a well and is then returned to the reagent stock, material from that well could be carried back into the stock solution.
A new tip should generally be used if:
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The tip contacts a sample
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The tip contacts a different reagent
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The tip touches liquid already present in a well
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The tip touches an unintended container or surface
In other words:
Do not focus only on how many times the tip has been used. Consider what the tip has contacted.
Pre-Wetting Does Not Mean Reusing a Tip Across Samples
Pre-wetting is a technique used to help improve pipetting consistency.
It involves aspirating and dispensing the same liquid several times before the final measurement so that the inside of the tip becomes conditioned to the liquid.
However, pre-wetting does not mean that the same tip can be reused across different samples.
Pre-wetting is a preparation step performed with the same liquid before pipetting.
When moving to a different sample or reagent, a new tip should still be used.
It is important not to confuse pre-wetting with repeated use of the same tip across different materials.
Can Filter Tips Be Used Longer?
Using a filter tip does not change the basic principles of tip replacement.
The primary purpose of a filter tip is to help reduce the risk of liquid or aerosols entering the pipette body.
This means that:
A filter tip does not eliminate the need to change tips between samples.
When working with a different sample or when contamination may have occurred, a new filter tip should be used.
The filter helps provide a barrier between the sample and the pipette, but it does not remove liquid or contamination from the exterior or lower portion of the tip.
Situations Where You Should Replace the Tip Immediately
Even when the sample or reagent has not changed, there are situations where replacing the tip is the safer choice.
The Tip Touches an Unintended Surface
If the tip touches the workbench, a glove, the outside of a container, or another unintended surface, contaminants may be transferred onto the tip.
Liquid Gets on the Outside of the Tip
If the tip is immersed too deeply or touches the wall of a container, liquid may remain on the outside.
Moving that tip to another container could transfer the external liquid into the next sample or reagent.
The Tip Becomes Deformed
The tip may become damaged if it is pressed too firmly onto the pipette or if it contacts the bottom or side of a container.
A change in tip shape can affect aspiration or dispensing behavior.
The Tip Feels Loose
If a tip is not attached correctly, air leakage may occur and affect the aspirated volume.
Rather than continuing with a tip that feels unstable, it is generally better to replace it and attach a new one correctly.
Contamination Is Suspected
If you are unsure whether the tip contacted another liquid or surface, replacing it is usually the safer choice.
Saving one pipette tip is rarely worth risking an entire experiment.
Does Using Fewer Tips Really Reduce Costs?
Because pipette tips are disposable consumables, reducing the number used can lower direct consumable costs.
However, if excessive tip reuse leads to:
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Sample contamination
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Contamination of reagent stocks
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Repeated experiments
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Sample disposal
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Reagent disposal
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Time spent investigating the cause of a problem
the total cost may be much greater than the cost of several additional tips.
At the same time, it does not necessarily make sense to change the tip after every single dispensing action when there is no meaningful contamination risk.
The goal should not simply be to use as many tips as possible or as few as possible.
The better approach is to establish tip-changing rules that match the experimental workflow and contamination risk.
Standardize Tip-Changing Rules Within the Laboratory
If each researcher decides independently when to change a tip, pipetting conditions may vary between operators.
For example, one researcher may use a new tip for every sample, while another may continue using the same tip across several similar samples.
This makes contamination risk more difficult to control consistently.
When multiple people perform the same workflow, it can be helpful to define:
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Which steps always require a new tip
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When the same tip may be used for repeated dispensing
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Which workflows require filter tips
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Whether a used tip may ever return to a reagent stock
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What to do when contamination is suspected
These rules can be included in SOPs or experimental procedures.
Tip replacement should be treated as part of the pipetting protocol rather than as an informal personal preference.
Think About What the Tip Has Touched, Not Just How Many Times It Has Been Used
There is no single number of uses that determines when a pipette tip must be replaced in every experiment.
A new tip should generally be used when:
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The sample changes
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The reagent changes
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Contamination may have occurred
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The tip contacts an unintended liquid or surface
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The condition of the tip is questionable
For repeated dispensing of the same reagent into multiple wells, continued use of the same tip may be appropriate under certain conditions.
When in doubt, ask yourself:
Do not count how many times the tip has been used. Think about what the tip has touched.
Appropriate tip replacement is not simply a matter of consumable management.
It is a basic part of pipetting practice that helps protect samples, reagents, and experimental results while reducing the risk of unnecessary repeat work.
WATSON offers a wide range of pipette tips for different laboratory applications, including standard, filtered, sterile, and various volume and packaging options.
By combining the appropriate pipette tip with clear replacement rules, laboratories can better manage contamination risk while maintaining efficient workflows.