Article written by Rebecca Lampert, Product Manager and Dominique Juall, Life Science Application Specialist at BRANDTECH Scientific
I. Introduction
Pipettes are essential tools in laboratories for liquid handling, enabling scientists to measure and transfer small volumes of liquid with high accuracy and precision. Selecting the right pipette involves considering various factors including pipette quality, ergonomics, ease of calibration, compatibility with available pipette tips, and of course whether it can deliver the accuracy and precision required for the intended applications.
The accuracy and precision of pipetting directly impacts the reliability and reproducibility of scientific experiments. Small errors in liquid handling can lead to significant deviations in experimental outcomes. Therefore, careful consideration for a routine calibration process of pipettes plays a critical role in ensuring that they perform optimally, aligning with manufacturer specifications or to the user’s standards.
II. Understanding Pipette Calibration
Pipette calibration involves verifying and adjusting pipettes to ensure that the volume of liquid dispensed matches the volume set within acceptable limits, thus guaranteeing reliable experimental results. Calibration is typically performed according to specific standards, with ISO 8655 being one of the most stringent and prevalent. This standard outlines the procedures and requirements for calibration of piston-operated volumetric equipment, including pipettes. ISO 8655 encompasses standards for environmental conditions and calibration equipment, the process for taking measurements, as well as setting/establishing allowable tolerances. Other methods of calibration might incorporate lab-specific protocols or manufacturer-specific guidelines, which can vary in stringency and methodology, including acceptable error ranges for various volume settings.
Since laboratories have their own set of standards to which they want their pipettes calibrated, they may opt to have calibration done either in-house, by a third-party calibration service provider whether on-site or in the provider’s facility, or by the pipette manufacturer. The choice of calibration standard and process can significantly affect the accuracy and precision of pipetting. ISO 8655, for example, mandates rigorous testing and precise measurements, ensuring high levels of accuracy. In contrast, other methods might be less stringent and lead to variations in pipetting performance. Each option has its own set of protocols and standards, and it is the responsibility of the laboratory to ensure the calibration method they select meets their requirements.
III. Best Practices & Importance of Proper Pipette Calibration
Proper calibration is essential for maintaining the accuracy and precision of pipetting. Calibration mistakes can undermine this process, leading to inaccurate volume measurements. To minimize these errors, some best practices include:
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Using the right tips
Different tips can affect the volume dispensed due to variations in fit. Typically, the pipette manufacturer produces tips that are the best fit for a pipette. Lower quality tips, though more cost effective, may cause tip fit issues and result in higher costs long term. Making sure that the tips used are of high-quality and are compatible with the pipette is essential. Moreover, calibration should be performed using tips that are intended for use with the pipette, as highlighted in the Application Note: Assessing Compatibility of BRAND® Transferpette® S Pipette with Third-Party Universal Pipette Tips. This practice ensures that the calibration reflects real-world usage, further enhancing accuracy and precision.
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Considering environmental conditions
Environmental factors such as temperature and humidity can impact liquid properties (e.g. density) and the accuracy of pipetting. The most stringent calibration is normally done in a controlled environment where these factors are considered in the final calculation to the measurements taken, and thus the adjustments made to the pipette, are reliable. Additionally, all materials must be allowed to equilibrate to the temperature of the environment to avoid discrepancies caused by temperature differences.
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Ensure consistent pipetting technique
Pipetting technique, including the angle of the pipette, immersion depth, and speed of aspiration and dispensing, should be consistent during calibration. Inconsistent techniques, especially by untrained personnel, can lead to variable results and inaccurate calibration.
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Taking sufficient measurements
To ensure statistical power, an adequate number of measurements should be taken. More stringent standards incorporate taking measurements at various volume settings of the pipette. A single measurement is not statistically adequate to determine accuracy and precision.
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Using only calibrated equipment
The equipment used to calibrate the pipette, such as balances or other measurement devices, should be regularly maintained and calibrated to provide accurate readings. Uncalibrated equipment can only add to errors in determining pipette performance.
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Adjusting pipettes correctly
Each manufacturer will have different protocols to adjust their pipettes during the calibration procedure. Properly training personnel or confirming that the third-party service provider is familiar with how to adjust the pipette according to the manufacturer’s specification is crucial.
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The consequences of improper calibration extend beyond inaccurate measurements. Improper calibration can lead to experimental inconsistencies and loss of reproducibility which therefore causes misleading conclusions and time inefficiencies. Thus, it would be prudent for a laboratory to examine the calibration services they utilize to confirm that it meets the requirements for their applications.
Additionally, routine calibration should be an integral part of pipette maintenance, ensuring that pipettes remain within their specified tolerances and continue to perform accurately. To help maintain calibration between scheduled checks, users should handle pipettes carefully, avoid rough usage, and regularly check for signs of wear and tear. Investing in devices such as the Brand® PLT (Pipette Leak Testing Unit) can provide added confidence that the pipettes on-hand are reliable during periods between calibrations.
IV. Conclusion
In summary, investing time in proper pipette calibration is critical for accurate and precise pipetting and is essential to the reliability of scientific experiments. By adhering to best practices, avoiding common calibration mistakes, understanding the impact of different calibration standards, and sticking to regular calibration checks, scientists can ensure that their pipettes perform to reliably to specification.
For trustworthy results, BRANDTECH offers BRAND® Transferpette® S pipettes with an ISO 8655 calibration certificate.
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