In microbiology, which micropipette should you use: variable or fixed volume?

According to our survey, the choice is clear among SuperMicrobiologists: 79% use variable-volume micropipettes in their microbiology labs.

In many fields, people say, “if you can do more, you can do less,” so one might think that a variable-volume micropipette would meet all needs.

But is it really necessary to use a variable-volume micropipette if you only pipette… one volume?

To help you make your choice, here’s a list of the pros and cons of each type of micropipette.

Fixed-Volume Micropipette

A fixed-volume micropipette is a tool used in microbiology laboratories to dispense a (single) very precise volume of liquid.

Since the volume is fixed, it cannot be adjusted.

Examples:

• P1000 for dispensing 1000 µL
  
• P200 for dispensing 200 µL
  
• etc…

Advantages of a Fixed-Volume Micropipette

Precision

A fixed-volume pipette is always more precise than a variable-volume pipette. All manufacturers agree on this point.

This doesn’t mean variable-volume pipettes lack precision; it simply means they’re slightly less precise.

For certain tasks, that small difference can matter.

Easier calibration

With a fixed pipette, calibration (metrology) only needs to be performed for one volume.

This is much simpler (and faster) compared to calibrating for 3 or 4 different volumes on a variable pipette.

No risk of incorrect settings

Let’s be honest: who hasn’t used a P1000 variable pipette set at 950 µL, thinking it was set to 1000 µL? Oops I did it again!

With a fixed-volume pipette, there’s no risk of incorrect settings—what you see is what you get.

Of course, if you grab the wrong pipette altogether, that’s on you…

Disadvantages of a Fixed-Volume Micropipette

Limited to a single volume

By design, the volume cannot be adjusted, which limits its flexibility for different tasks.

Variable-Volume Micropipette

The air-cushion variable-volume micropipette is a precision instrument used to measure and dispense liquids. Unlike fixed-volume pipettes, the volumes can be adjusted by the user.

Each pipette has a specific operating range. In microbiology labs, the most common ranges are:

• 10 to 100 µL
  
• 20 to 200 µL
  
• 100 to 1000 µL

Advantages of a Variable-Volume Micropipette

One pipette, multiple volumes

This is undoubtedly the biggest advantage of variable-volume micropipettes. Owning a single pipette brings multiple benefits:

• Cost efficiency: One pipette instead of two or three reduces expenses.
  
• Space-saving: Fewer pipettes mean less mess on the lab bench.

Disadvantages of a Variable-Volume Micropipette

Slightly less precise

The further you move away from the nominal volume, the less precise the micropipette becomes (compared to a fixed-volume pipette).

Accuracy tends to decrease significantly below 10% of the nominal volume. The ideal range is between 35% and 100% of the nominal volume.

Time-consuming adjustments

Switching between volumes takes a bit of time, especially if you’re frequently changing settings.

Risk of errors

It’s possible to pipette the wrong volume if:

• The dial isn’t set correctly
  
• The volume accidentally shifts
  
• You simply forget to double-check your settings.

These errors are rare but can happen when your mind is elsewhere.

Longer calibration process

Calibrating a variable-volume pipette is more complex because multiple volumes need to be tested.

Typically, metrology involves checking:

• The minimum volume (10%)
  
• The nominal volume (100%)
  
• Half the nominal volume (50%)

Conclusion : Which air-cushion micropipette should you choose?

Once again, there’s no one-size-fits-all answer—it all depends on your specific needs.

Before making a decision, take a moment to list the volumes you’ll need to pipette at each workstation.

• For routine work (e.g., quality control labs):
  If you’re often working with the same volumes, simplicity is key. The goal is to repeat the same actions without overthinking. In this case, fixed-volume micropipettes are the best choice.
  
• For R&D labs:
  In research and development, volumes tend to vary frequently. Here, variable-volume micropipettes are the preferred option for their versatility.

Choosing the right tool is all about matching it to your workflow! 😊

What about you ? Which micropipette do you use in your lab ?