Finding the perfect pipette and optimizing its use depends on a myriad of factors—some obvious, like the importance of precision and accuracy, and some more specific, like the ability to use the pipette while it is charging. We recently asked a handful of pipetting experts to help us compile a comprehensive list of things to consider when purchasing pipettes and maximizing their use. Their tips and tricks range from how to avoid repetitive stress injuries to how to select and seat pipette tips. We hope you find their guidance useful and applicable in your laboratory.
There is a reason that pipettes are called lab workhorses. They are used often and relied on heavily. Although the average pipette lifespan is said to be around 7 years, Drummond Scientific has reported some units are still in operation 15 to 20 years after purchase. Whether the pipette will be used every hour of every day or just once or twice a day, pipetting options should be researched carefully and expectations defined before purchasing.
Matching lab needs
Questions you should ask yourself before starting the purchasing journey include: Is a single-channel or multichannel pipette best for my needs? And: Do I prefer fixed or variable volume? Workload will likely dictate whether you choose a manual or electronic pipette or want to consider an automated solution.
According to Gilson, the type of analysis that needs to be performed, the physical properties of the liquid, and the volume to be handled determine pipette choice. They recommend selecting a pipette with a nominal (maximum) volume as close as possible to the desired volume to transfer.
Also, regardless of the required volume, physical properties of the liquid directly impact precision and accuracy. Air displacement pipettes are the right choice for aqueous liquids whereas positive displacement pipettes are the perfect solution for viscous, volatile, hazardous, hot, and cold liquids.
Nicholas Kennish, sales manager at Drummond Scientific, suggests considering the following:
- Ease of use
- Ergonomics
- If the unit has certain speed controls for aspirating and dispensing
- How long a unit operates on a single charge
- Manufacturer support for replacement parts/technical service
- Ease to change out simple parts such as the filter or battery
- Whether the unit can be used while charging to reduce downtime
For Grace Soong, product marketing manager at VistaLab Technologies, an important consideration is the amount of time spent pipetting. For people who are doing a lot of pipetting, “it is also extremely important to consider the posture and arm and hand position to reduce risk of repetitive stress injury (RSI) or even just discomfort and pain while pipetting.”
VistaLab’s pipettes were designed to reduce hand and grip stress. “They are contoured to hold comfortably, but also have an adjustable hook to ‘hang’ on your hand, effectively decreasing the weight as well as decreasing grip force,” Soong explains. “Ergonomically designed pipettes should allow you to decrease discomfort, pain, risk of injury, and injury while pipetting. Feeling better will allow you to work more comfortably, which should increase your efficiency and productivity.”
Irregular pipetting rhythm and timing during pipetting can affect accuracy by up to 1.5%, according to Gilson. When pipetting in a high-throughput setting, it is important to have reliable results and to be as efficient as possible. In addition to having the right pipette, Gilson strongly recommends maintaining an appropriate posture, good workspace organization, and the appropriate technique to achieve the best results.
Extending lifespan
It is inevitable that pipettes will falter and ultimately fail. Whether that takes 5, 15, or even 40 years depends on many factors, but with proper care and maintenance a pipette can aspirate and dispense liquids for quite a long time. Some actions, however, are likely to damage your pipette and should be avoided, especially pounding tips onto your pipette and over-aspiration.
Gilson recommends that all customers service their pipettes on at least an annual basis, regardless if the pipette is a year old or 40 years old. During this service, the technician can evaluate the pipette for performance and function, perform repairs and adjustments to calibration as needed, and potentially help avoid costly repairs to the pipette.
Product demonstrations
Product demonstrations can be very useful in making pipette choices, and several companies, including VistaLab and Gilson, offer them.
VistaLab offers a 2-week free trial for Ovation pipettes because, as Soong explains, “we understand that the design and shape is so unlike all the other pipettes out there (all axial), it is something that scientists may need to try out and get used to before purchasing. Feedback and reviews have told us though that even if the learning curve is a little higher than for other pipettes, it is well worth it!”
Gilson also offers product demonstrations for all their pipettes. “During a demonstration, we can show all the unique qualities of each pipette and take the time to talk with the customer about what pipette line will fit their needs. This gives us the opportunity to work with the customer and make sure they are getting the right product.”
Manual vs. automated
There often comes a point where automated pipetting makes more sense than manual pipetting. Ryan Rebo, product support specialist at Hamilton, and Rouba Najjar, consumables product manager at Hamilton, explain when you should start looking into automated pipetting instead of manual pipetting as well as the differences between manual and automated pipetting.
Pipetting is so much more than a simple transfer of liquid from one place to another. In fact, Najjar explains, with an almost endless number of impactful variables, it’s practically an art form. “Manual pipetting, especially in the hands of a practiced user with good technique, offers the advantage of visualizing the process and being able to somewhat vary the dispense/aspirate speed, height, or position in the sample or target vessel. Of course, the downside is inconsistent results, low throughput, and the potential for repetitive motion injuries. There’s no hard and fast rule, but when a lab decides that their reproducibility, throughput, and user comfort levels are no longer acceptable, it’s time to transition to an automated system.”
Full automation becomes necessary when the demands of a process require many samples to be processed with low variability, Rebo explains. “However, if a lab has a lot of samples to process, with each having a unique consideration, full automation might not be the right fit for the laboratory due to the initial cost of automation and the time needed to program and optimize the method.” In that case, Hamilton has a third option called semi-automation that is quicker to program and validate, and amenable to labs with more variability in their processes.
Suggestions on Selecting and Seating Tips
- The specific lab application can help to steer tip type, whether it’s sterile, filtered, low-retention, wide bore, or more.
- It’s important to remember that the pipette and tip work together as a system. This means that the tip type and brand that were used during pipette calibration should be the ones used in operation. If another tip type or brand is used, the pipette should be immediately recalibrated.
- The liquid being pipetted is also an important consideration in tip selection. As liquids deviate from the calibration liquid in terms of viscosity, temperature, surface tension, hydrophobicity, and more, differences in tip quality can impact results.
- A high-quality tip is manufactured to tighter tolerances with superior surface finishes and consistency in parameters, such as the tip orifice, compared to many off-brand tips.
- People commonly jam tips onto a single-channel pipette with too much force. This increases hand strain and makes it more difficult to eject the tips after use. We recommend a light double tap to quickly and reliably seat the tip using the pipette’s momentum without excess exertion that can contribute to fatigue.
- When it comes to multichannel pipettes, the tips should be racked with a reinforced frame to aid in proper alignment. Without that rigid frame, the tips can bow, or misalign, under the strain of a multichannel pipette when seating the tips.
- Proper tip seating is just as important in an automated pipetting system as it is with manual pipettes. A very tight lock-and-key type seal ensures precise tip positioning and helps the robots to monitor liquid levels to a high degree of accuracy. This also helps to minimize or eliminate aerosol creation when unseating the tips.
Tips provided by Ryan Rebo, product support specialist, Hamilton Company.