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For liquid handling quality assurance, where you calibrate impacts what you measure.
High-profile drug failures and mushrooming costs have led to growing scrutiny of the pharmaceutical industry. While drug manufacturing has always faced intense regulation, the push for quality and efficiency is moving upstream. Companies are striving to build greater quality into drug discovery and development processes driven by the Process and Analytical Technology (PAT), Corrective Action Preventive Action (CAPA), and other initiatives.
Liquid handling devices are used frequently in pharmaceutical laboratories and play an important role in data accuracy. Device verification and calibration are essential cornerstones of laboratory quality assurance programs. Liquid handling technologies keep improving, volumes get smaller, and processes are becoming increasingly automated. Regulations are not keeping pace with new technology, leading to a lack of relevant calibration standards or guidelines. However, laboratories need to update their calibration procedures to measure and document microliter/nanoliter volumes quickly and accurately.
The real estate adage “location, location, location” applies to liquid handling quality assurance. And by location, what exactly do I mean?
The location where the instrumentation calibration or verification process actually takes place is critical. The performance of liquid delivery devices must be verified in the laboratory in which they are used since environmental conditions can have a significant impact on pipetted volumes and are a major source of laboratory error. As laboratories work with smaller liquid volumes, the risk of error grows since microliter quantities are more sensitive to volume variation. Inaccuracy of just one microliter can significantly alter research results.
The impact of environmental conditions on pipetted volumes is due largely to the mechanical operation of liquid handling devices, which often function through air displacement. In these devices, air acts as a spring that connects the piston to the liquid and pulls the liquid up into the tip. Air is affected by altitude (barometric pressure), temperature, humidity and other environmental conditions. Environmental conditions can affect how much liquid is pulled into the pipette tip and subsequently dispensed.
To understand the implications, consider a laboratory in Denver that outsources pipette calibration to a service based on the California coast. The pipettes are shipped to the sea-level laboratory and calibrated in that lab’s highly-controlled environment. When the newly-calibrated pipettes are returned to the Denver laboratory, they will most likely under-deliver because the less-dense air at the higher altitude will not pull as much liquid into the tip. This will reduce delivered volume and affect data integrity. The approximate baseline barometric pressure between San Diego, CA (elevation 0 feet) and Denver, CO (elevation 5,280 feet) is shown in the table below:
Pressure Delta vs. Sea Level
|Altitude||In Hg. Abs.||MM Hg. Abs.||In Hg. Abs.||MM Hg. Abs||%|
Of course this is subject to daily variability basic on specific conditions, so the actual variance in barometric pressure may be more or less than the baseline on any given day.
By measuring liquid delivery devices in place of use, laboratories can uncover how environmental conditions are affecting instrument performance and adjust devices accordingly to maintain accuracy and precision. The calibration technology must be robust and unaffected by the environment.
Multiple laboratory locations
The impact of location on data integrity does not stop here. Globalization and the increasing use of contract research and manufacturing services has a great impact. As a result, there is an urgent need for standardized and transferable methodologies. As drug companies spread laboratory operations across borders and to outsourced partners, effective communication and harmonization of laboratory practices become crucial. A company must integrate a standardized calibration methodology to facilitate consistency and compatibility across laboratories in its organization. This will ensure that one microliter dispensed from an automated liquid handler in India is the same as one microliter dispensed from an automated liquid handler in San Francisco.
As globalization and outsourcing grow, international organizations are emerging to provide border-spanning guidance to companies operating in multiple countries. The International Organization for Standardization (ISO) is recognized as a key global guiding body for a range of industries, particularly laboratories. A non-governmental organization, ISO includes an international network of experts that identify and adopt relevant standards that can improve practices and ensure quality in products and services. These standards enable international companies to coordinate laboratory operations and maintain consistent quality programs worldwide.
ISO has released standard 8655, recommending calibration technologies for various applications. Gravimetry, which weighs liquid volumes on balances to verify volumes, is noted in Part 6 of this standard. However, gravimetric methods are susceptible to vibration, evaporation, and other factors. To use gravimetry effectively a number of monitors, adjusters (Z-factors), and even facility requirements must be considered. In Part 7, ISO recognizes that photometry, which utilizes light absorption to verify volume accuracy, is not affected by environmental conditions such as air drafts and vibration and is “particularly well-suited for small volumes.”
Trust in results
To truly trust data, laboratories need effective liquid handling quality assurance programs. Understanding how laboratory conditions affect instrumentation, measuring and monitoring laboratories to establish baseline conditions, coupled with standardizing procedures across laboratory locations can reduce errors that can develop in liquid delivery apparatus.
About the Author
George Rodrigues, Ph.D., is senior scientific manager at ARTEL.
Filed Under: Drug Discovery