Why Pipette Calibration is Essential?

Pipettes are vital tools used in chemistry, biology, and medical laboratories to accurately measure and transfer specific volumes of liquid. It is available in various types, from simple narrow-graduated glass tubes to more advanced adjustable single-channel and multi-channel to electronic pipettes. They help dispense 10 ml or greater to 1μl or fewer volumes of liquid. 

Why Calibrate Pipettes?

However, the pipette is a mechanical lab tool that gradually loses its ability to provide accurate results. It is simply due to the wear and tear and when this happens you get unreliable results. Thus, it is vital that you consistently calibrate your pipettes as it is essential lab practice to ensure greater quality results. 

The main object of pipette calibration is to ensure that aliquoting and dispensing are carried out with precision, maintaining accurate results, and longevity of the pipette. 

How Often Should You Calibrate the Pipettes?

Pipette calibration varies depending on how often the pipette is used and the type of liquids dispensed. However, to ensure consistent accurate, and reliable results, it is vital to perform calibration every six months. 

To determine calibration frequency, a formula known as MTBF (Mean Time Between Failures) is used. To determine MTBF, a group of pipettes is analyzed. They are studied to observe how long it takes each of them to fail. A failure is a performance that falls below established standards and the mean of the collective failure times is the MTBF for those pipettes.

MTBF is a reliable way to calculate the time between calibration services. However, your lab should establish a schedule for pipette calibration.

Pipette Calibration Principle

At a temperature of 20°C (68°F) and one atmosphere of pressure, the density of water stays constant at 1 g/mL. It means the volume of water is determined by weighing the sample of dispensed water.

However, shifts in temperature, humidity, and atmospheric pressure can influence the accuracy of measurements. The impact of pressure is negligible in practice, but the temperature should be taken into attention. The factors are combined to calculate the Z-factor or Z correction factor. It is a translation factor applied in the calculation of the volume of water to verify the mass of the dispensed sample and the accuracy of the pipette.

Procedure for Pipette Calibration 

The most utilized method for pipette calibration is gravimetric analysis. It involves dispensing distilled water samples into a container and the weight of the water measured by a precision analytical balance. Gravimetric analysis is a favored method by various laboratories as it is simple and includes the traceability of the distilled water is an absolute standard.

 However, temperature changes in the testing environment or equipment may considerably influence the calibration. Therefore, the distilled water and pipette must be placed in the calibration environment an hour before starting the calibration process so the equipment can adjust to the temperature. Also, make sure that the environment is kept constant throughout the calibration procedure.

As you just read that the calibration process can be a bit difficult, and one mistake can lead to errors. Thus, it is better to hire professional calibration services as they guarantee the pipette reaches its maximum potential and abides with the International System of Units (SI). Also, they work under a controlled temperature facility that ensures all ISO protocols are followed. 

For more tips and tricks to get your experiments done, check out the Microlit website.