In Liquid Handling Quality Assurance, All That Matters is Location, Location, Location
By Rodrigues, G. | Publication
A number of high-profile drug failures and mushrooming costs have led to growing scrutiny of the pharmaceutical industry. While drug manufacturing has always faced intense regulations, the push for quality and efficiency is moving upstream. Driven by PAT, CAPA and other initiatives, companies are striving to build greater quality into drug discovery and development processes.
Liquid handling devices are among the most frequently used instruments in pharmaceutical laboratories and play an important role in data accuracy. For these reasons, device verification and calibration are essential cornerstones of laboratory quality assurance programs. However, liquid handling technology is advancing rapidly, handling smaller volumes and becoming increasingly automated. And this is producing several effects. First, regulations are not keeping pace with new technology, leading to a lack of relevant calibration standards or guidelines. In addition, laboratories need to update their calibration procedures to measure and document microliter/nanoliter volumes quickly and accurately.
To help you navigate the rapidly evolving world of liquid handling, I’d like to offer some advice. In liquid handling quality assurance, all that matters is location, location, location. Okay, location is not “ALL” that matters, but it’s certainly important. And by location, what exactly do I mean?
Of great importance is where the instrumentation calibration or verification process actually takes place. It is critical that the performance of liquid delivery devices be verified in the laboratory in which they are used. This is because environmental conditions can have a significant impact on pipetted volumes and are a major source of laboratory error. This risk of error is growing as laboratories work with smaller liquid volumes, since microliter quantities are more sensitive to volume variation. In today’s laboratory applications, inaccuracy of just one microliter can significantly alter research results.
The impact of environmental conditions on pipetted volumes is largely due 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 labs highly controlled environment. Pipettes are returned to the Denver laboratory newly calibrated. However, they will most likely under-deliver. This is because air is less dense at higher altitudes. Less dense air will not pull as much liquid into the tip and 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) are shown in the tables below:
Of course this is subject to daily variability based on specific conditions, so the actual variance in barometric pressure may be more or less than the baseline on any given day.
(Note: 5,000 feet and 10,000 feet elevation data was shown as there are few labs currently at or above 10,000 feet elevation. There are many, et al be the number unknown, labs at or above 5,000 feet elevation.)
On the other hand, by measuring liquid delivery devices in their place of use, laboratories can uncover how environmental conditions are affecting instrument performance and adjust devices accordingly to maintain accuracy and precision. In order to calibrate liquid delivery devices in the laboratory, 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. The pharmaceutical industry is greatly affected by globalization and the increasing use of contract research and manufacturing services. 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 for market success. Companies must integrate a standardized calibration methodology to facilitate consistency and compatibility across laboratories in their 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 the vast number of companies operating in multiple countries. For example, 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, this body 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 are highly useful for international companies to coordinate laboratory operations and maintain consistent quality programs worldwide.
With regard to liquid handling, 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 and evaporation among other things. 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 un 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 at least establish baseline conditions, coupled with standardizing procedures across laboratory locations can reduce the error that can develop in liquid delivery apparatus.
About the Author
George Rodrigues, PhD, is Senior Scientific Manager at Artel, a leading innovator in liquid delivery quality assurance.