The hidden risk: only 5 to 10 % of all
pipette failures are obvious to the user.
Pipette Servicing – Are You Missing the Point?
Pipettes are everywhere you look in virtually every life sciences laboratory; they are the very foundation of many laboratory processes and assays. But, perhaps for that reason, everyone just assumes that they are simple, foolproof tools that look after themselves. After all, using a pipette is easy, as automatic as walking or breathing – you just do it without thinking and the pipette does what you want it to do.
Or does it?
What’s hidden under the surface?
In reality, the data that METTLER TOLEDO has accumulated over several years suggests that a significant proportion of pipettes are not serviced on a regular basis, even though the integrity of your results highly depends on the performance of your pipettes and only a small fraction of failures are evident to the pipette user. When a pipette is dripping, there’s obviously something wrong; likewise if you set your pipette at 100 μl and it only aspirates 20, you know there’s a problem. However, we estimate these fundamental breakdowns account for only a fraction of the total failures; a large number of failures are caused by tiny cracks in the seal or a buildup of dirt that affects the piston, faults that go unnoticed, except to the trained pipette technician.
In fact, an estimated 95 % of pipette failures can be attributed directly to a pipette‘s sealing system, comprising of the seal / O-ring, shaft and piston (Figure1). Comprehensive annual preventive maintenance, ensuring that all sealing system parts are checked and replaced with original manufacturer parts when needed, is the only way to ensure your pipette can perform to its designed specifications.
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Figure 1: Performance failure causes
It works, but is it accurate?
Every lab has different priorities, but surely the one factor linking them all, and therefore the most important reason for everyone to regularly calibrate their pipettes, is to make sure that all data points are correct, ensuring that what they’re measuring is real. And what it all comes down to in the end, is how accurately and reproducibly those tiny amounts of liquid were transferred from one place to another. In this respect, it is the small, hidden faults that can have most impact on your science. Where a variance in performance of ± 5 % may be acceptable for one experiment, it might not be for another.
This inaccuracy could make a fundamental difference to your data, for example, when establishing a standard curve, and when amplified in serial dilutions. Worse still, this error could pass largely unnoticed and, depending on the significance of the data, could lead to incorrect results, your published data being challenged or, at the very least, such a degree of variation that the experiment needs to be repeated multiple times…
Saving time and money
…which leads nicely onto the next biggest reason to calibrate regularly; to save, or at least not waste, your valuable resources. Once a fault has been identified, the time, amount of work and cost of materials required to repeat experiments could be devastating. Whether you’re working with precious or expensive sample and reagents, or organizing a protocol that takes weeks to set up, no lab wants to start again from scratch.
All of these problems can easily be avoided by establishing a rigorous performance strategy, including regular preventive maintenance and calibration on many levels. What differs significantly between laboratories is the frequency at which maintenance, verification and calibration should ideally take place.
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Figure 2: A risk-based approach to pipette maintenance
In pharmaceutical QA, diagnostic and other laboratories that routinely audit equipment in order to comply with stringent regulatory guidelines, pipette service is carried out far more frequently than in, for example, academic research departments. In general, the frequency depends largely on the significance of something going wrong with your pipette, illustrated simply in Figure 2 below. The relationship is simple; if your application depends on rare samples, costly procedures and/or the accuracy of the results is critical, then you should check your pipettes frequently. Ask yourself this: how many weeks or months of data am I willing to put at risk? To help you create a pipette performance plan talk to your METTLER TOLEDO representative for more information.
Good Pipetting Practice – the art of getting it right
Keeping your pipettes in top shape is just one part of a comprehensive pipetting performance strategy. Other key issues include using the correct pipetting technology for a given kind of experiment, maintaining a proper pipetting technique to get the most consistent results, and concentrating on posture and handling to achieve good user ergonomics. Using our many years of experience and data accumulated over that time, METTLER TOLEDO has developed a pipetting risk assessment tool which provides a complete report on your particular pipetting risks, and can advise on how to mitigate them. There is also a series of informative and helpful workshops and seminars on Good Pipetting Practice (GPP), held locally in several countries, which tackle many of the challenges discussed here, and include risk assessment and how to establish a manageable strategy for routine operation calibration in your lab.