As Found measurements show how the pipette was performing when it arrived for calibration. As Left measurements show how it performs after calibration, maintenance and any necessary adjustments.
Together, they provide a more complete picture of pipette performance and can help identify issues that a simple pass/fail result might miss.
What Does As Found Mean in Pipette Calibration?
As Found is the pipette’s measured performance before it is adjusted or serviced.
This gives you a snapshot of how the pipette was actually performing at the end of its calibration interval.
For example, if As Found testing shows that a pipette is outside your established tolerance, that information may be important even if the pipette can be adjusted successfully. It tells you that the instrument was not performing within the specified tolerance when it arrived for calibration.
Depending on your laboratory’s procedures and how the pipette was used, that may warrant a closer look at work performed since its previous calibration.
What Does As Left Mean?
As Left is the pipette’s measured performance after calibration, maintenance and any necessary adjustment.
These measurements document the condition of the pipette at the completion of service.
A pipette can therefore fail its As Found testing but pass its As Left testing. In that situation, the two sets of results tell the full story: the pipette arrived outside tolerance, was serviced or adjusted, and was performing within the applicable tolerance when calibration was completed.
Why Do You Need Both As Found and As Left Measurements?
Looking at both measurements provides a more useful calibration history than looking only at the final result.
As Found tells you where the pipette started. As Left tells you where it ended.
Together, this information can help laboratories:
- Identify pipettes that have drifted outside acceptable tolerances
- Evaluate whether an out-of-tolerance condition requires further investigation
- Track pipette performance across calibration intervals
- Identify recurring performance problems
- Document performance before and after adjustment or service
This can be particularly valuable in laboratories where pipette accuracy directly affects testing, research or quality processes.
What Happens if a Pipette Fails As Found Calibration?
An out-of-tolerance As Found result means the pipette did not meet the applicable acceptance criteria when initially tested.
That does not automatically mean previous test results are invalid. However, it gives the laboratory information it may need to evaluate the potential impact according to its own quality procedures.
The pipette may then be cleaned, maintained, repaired or adjusted as necessary and tested again. The final As Left measurements document its performance after that work has been completed.
This is why retaining the original As Found data matters. Adjusting a pipette can correct its current performance, but it cannot tell you how it was performing before the adjustment.
As Found vs. As Left: A More Complete Calibration Record
It can be tempting to look at a pipette calibration certificate and ask one question: Did it pass?
But calibration data can tell you more than that.
As Found measurements document the pipette’s condition before intervention, while As Left measurements document its performance after service. Comparing the two gives laboratories a clearer record of instrument performance and can help identify trends or potential problems over time.
The next time you review a pipette calibration certificate, don’t look only at the final result. Look at where the pipette started, too.
Pipette Calibration Services
Lab People/The Scale People provides calibration services for pipettes and liquid handling devices, with service options that include As Found and As Left measurements as well as NIST-traceable and ISO calibration options.
Choosing the appropriate calibration level depends on your equipment, application and quality requirements.
Need help determining the right pipette calibration service for your laboratory? Contact Lab People to discuss your pipettes and calibration requirements.