Pipettes are the workhorses of all labs that work with small amounts of liquids. Multiple times every day, researchers measure and move around liquids ranging from milliliters to nanoliters. As with other mechanical gadgets, pipettes become weary and error-prone with use.
Most pipette failures are silent. It is often not evident to the user that there is something wrong with the pipettes. With many experimental protocols lasting weeks or months, early pipetting mismeasurements can propagate to adversely impact a large part of a research project.
The better-safe-than-sorry approach is to not wait until the pipettes become noticeably faulty. Instead, routinely calibrate your pipettes (or have them calibrated by a service provider). But how often should you do it?
Calibrate pipettes often
Calibrating pipettes entails (1) verifying they are dispensing correct volumes, and (2) performing repair and maintenance if required. The desired frequency of this exercise depends on a few factors, such as how often you use them, the kinds of reagents you pipette, or how you store your pipettes. For most small academic labs with moderate academic use, calibrating pipettes once a year is considered enough.
But if many users share the pipettes and work with a variety of reagents, it may be prudent to calibrate your pipettes more frequently. For instance, pipetting viscous or volatile reagents could lead to a faster drop in the pipettes’ performance.
While calibrating pipettes in-house makes sense for small labs, it is generally more economical to get pipettes calibrated by dedicated service providers. This ensures that your pipettes are calibrated to the degree of compliance and accuracy required for your work.
Most pipette failures are silent. It is often not evident to the user that there is something wrong with the pipettes.
However, even a newly calibrated pipette may dispense the wrong volumes. This is why it is crucial to regularly verify the calibration.
...and when needed
Verifying if a pipette is dispensing the correct volumes is easy and takes only minutes. Dispense different volumes of distilled water and weigh them using an analytical scale. If the pipette is working fine, the weight should match as expected from the density of distilled water (accuracy), and the same volume when dispensed more than once should weigh the same (precision).
If either accuracy or precision is off the mark, the pipette needs recalibration. Pipette verification can also be done on a regular basis for all pipettes or for particular pipettes before a critical experiment.
For a set of pipettes, tracking how often they fail over years of usage gives a measure of mean time before failure (MTBF). A pipette failure is any loss of accuracy and precision beyond limits deemed tolerable for your work. MTBF allows you to figure out how often to calibrate your pipette set as well as identify which pipettes need calibration more often.
Well-calibrated pipettes ensure that you have confidence in your liquid measurements and that your research results are accurate and reproducible. This is why calibrating pipettes often and when needed is critical to your lab’s success. Designing a pipette calibration schedule requires considering the pipetting need and frequency of your team.
Moreover, regular pipette calibration is good for pipette health. Ensuring pipettes perform at their best for longer improves their longevity as well.