How to Calibrate a Pipette

This log documents how to calibrate a pipette in a regulated laboratory setting. Reliable pipetting results depend on three factors — the equipment used, the procedures followed, and the environment in which calibration is performed. Use this log to record instrument details, the calibration procedure, reference standards, measured results, maintenance activity, out-of-tolerance actions, and final approval for each calibration event.

Instrument Details

Record the identifying information for the specific pipette under calibration before you begin. Capture these details from the pipette label and your lab's equipment inventory.

Calibration Schedule

Before starting, confirm your calibration frequency, due date, procedure reference, and the role responsible for performing the work. Set up your workspace so that all required equipment is within easy reach.

Pipette calibration procedure

1. Pre-wet the pipette tip by aspirating and dispensing distilled water three to five times before starting calibration. This eliminates evaporation of water into the airspace inside the pipette.
2. Place the balance, pipette tips, and water within reach.
3. Hold the pipette vertically when aspirating water to ensure the correct volume is drawn.
4. Tare (zero) the balance before starting. Calibration software may perform this step automatically.
5. Hold the pipette at a 45-degree angle when dispensing water onto the balance for optimal accuracy.
6. Hold the pipette tip against the wall of the vessel and expel the entire sample. This is especially important for small sample volumes.
7. Maintain an even rhythm and consistent timing throughout the process to ensure reliable results.

Perform calibration in a stable, draft-free environment with constant temperature and humidity to reduce environmental effects on your measurements.

Use the same procedure for every calibration session. Consistency in technique is essential for achieving the best calibration results.

Standards Used

List the reference tools and materials used to perform calibration, along with their traceability information (certificates, expiration dates, lot numbers as applicable).

Confirm the presence of the balance, distilled water, disposable tips, and calibration software running on a computer at your workstation before proceeding.

Calibration Results

Record the measured values, acceptance limits, pass/fail status, and analyst initials for each calibration run.

Maintain an even rhythm and consistent timing throughout each run to minimize variability and improve measurement accuracy.

Follow the correct technique throughout: pre-wet the tip, hold the pipette vertically when aspirating, and position it at a 45-degree angle when dispensing into the vessel on the balance. These steps are crucial for minimizing errors caused by evaporation and for ensuring accurate volume delivery.

In addition to accuracy, evaluate the pipette for precision — the consistency of dispensed volumes across repeated runs. Precision is affected by the calibration environment, the repeatability of the procedure, and the skill of the person performing the calibration.

Use the analytical balance and calibration software to record each measurement for traceability. For example, a balance reading of 0.04999 g should be documented as shown.

Maintenance

Document any preventive maintenance, adjustments, repairs, or parts replaced, along with the service provider responsible.

If accuracy cannot be achieved through adjustment, use a calibration tool to adjust the pipette: turn the adjustment mechanism clockwise to increase the dispensed volume, or counterclockwise to decrease it.

When attaching tips to the pipette, do not twist the pipette — only press down to connect the tip securely. Twisting can damage the pipette or the tip and affect accuracy.

Out-of-Tolerance Actions

If you cannot adjust the pipette sufficiently to correct an accuracy error, inspect it for leakage, wear, damage, or mechanical malfunction. Do not proceed with calibration or return the pipette to service until it is confirmed to be in good working order.

Always consider the three critical factors for reliable calibration when investigating an out-of-tolerance result:

• Equipment: Properly maintained and calibrated pipettes, analytical balances, and calibration tools.
• Procedures: Standardized, validated calibration protocols followed consistently.
• Environment: A stable, draft-free, clean laboratory with controlled temperature and humidity.

Approval

Always obtain a calibration certificate after performing calibration. The certificate documents the results, the equipment used, and the personnel involved. An accredited certificate will also indicate the measurement uncertainty of the instrument.

Collaborate with colleagues during calibration to ensure procedures are followed correctly and to cross-check results. Discuss any issues or uncertainties with your team to maintain high standards of accuracy and reliability.

Once all calibration steps are complete and results are documented, power down the equipment, clean the workspace, and store all tools and pipettes properly for future use.