Repeatable Accuracy Depends on the Right Maintenance
The tools for pipetting evolved from clunky to sophisticated in fairly short order. These tools now allow for working accurately and repeatedly with multiple samples across a wide range of volumes. To get those high-tech capabilities, though, the tools must be properly maintained.
To stay precise and perform as desired, pipetting tools must be clean. “Have a standard everyday care protocol,” says Melissa Waldroup, product manager, life science at Cole-Parmer (Vernon Hills, IL). “If you use acids, for example, make sure to clean your pipettes daily.”
Even simple improvements in care can make a difference. “One of the key things that we recommend is to hang up your pipettes in their holders,” says Savio Gadelha, service product manager at Rainin Instrument, a METTLER TOLEDO company in Oakland, California. “That way, gravity pushes down any liquids.” He adds, “That’s simple, and it doesn’t cost you a thing.”
Many things can contaminate these tools. Waldroup says, “Contamination or breakdown of the pipette can happen over time, because inorganic acids and alkalines will break down plastics.” Some applications require special care. As an example, Gadelha says, “Forensics users tend to be the most common users of DNA decontamination services.”
Keep it calibrated
“Calibration is key,” says Waldroup. “If you don’t calibrate the device, then the accuracy and precision could be off.” Sometimes a measurement that is off by even a little matters. “When an inaccurate pipette is used to make FDA-regulated products, there may be a hold on product shipments or even a recall,” says Gadelha.
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Some scientists calibrate their own pipettes, and Waldroup says, “You can calibrate your own devices for the vast majority of mechanical and electronic pipettes.” Still, it can take some getting used to, because the tool must be taken apart, and “you need to make sure the adjustments are right, and you need to do repeat testing,” Waldroup explains.
Some companies recommend sending pipettes in for service rather than doing it yourself. “For the most part,” Gadelha says, “we don’t recommend that people open the pipettes, because there are lots of parts inside that they might not be familiar with and not know how they go back together.” He adds, “We offer a variety of services, including preventive maintenance, which is mostly general maintenance, and we replace some key parts that are tied to about 95 percent of the failures.”
How often a pipette needs calibration depends on how much it gets used. At the University of Wyoming in Laramie, molecular biologist Jesse “Jay” Gatlin uses a range of pipettes in his lab, and he gives them to Indianapolis-based Integrated Instrument Services for an annual cleaning and calibration. Paul Mooney, a graduate student in Gatlin’s lab, says, “Integrated Instrument Services will clean, repair, and calibrate single-channel pipettes for $18 per pipette.”
When looking for someone to care for your pipetting tools, Nicole Anderson—service operations manager at Gilson (Middleton, WI)—gives some suggestions. First, she says, “Performing regular service and maintenance is the best way to ensure a pipette remains accurate throughout its life span.” She adds, “Regular maintenance includes replacing wearable parts, such as O-rings and seals. After maintenance is performed, the pipette should also be checked for accuracy and calibrated.”
As an example, Gadelha says that Rainin has “six- and seven-digit balances, which are required to calibrate [2- and 10-microliter] pipettes, and multichannel balances for multichannel pipettes.” He adds, “When we service Rainin pipettes with dry seals, we upgrade them to the new lip seal free of charge.” In fact, Rainin pipette service includes “up to $50 in parts and/or labor for repairs,” he says.
Reducing user error
Getting an accurate result depends on the user as well. “You have to follow best practices—for example, how you hold the pipette,” Waldroup says. Following proper use protocols is especially important with micro volumes. “With larger volumes, you can almost visualize as a double check,” Waldroup says. “For 0.1, you can’t eyeball it, and you need to know that it’s 100 percent accurate.”
Experience and training also matter. Anderson says, “It takes considerable time and resources to train new employees on proper pipetting technique.” She adds, “Misuse can lead to inaccuracies and even damage to a pipette.”
In fact, some of the pluses of today’s pipettes can spawn challenges in accuracy. “Most labs today carry many different brands of pipettes,” Anderson says. “This variety allows the users to find a pipette that works for them but can make it difficult for a department to develop a comprehensive standard operating procedure for pipette service and maintenance.”
Know your tools
Asked what top tip she’d give to pipette users, Waldroup says, “There are so many different types of pipettes that it’s difficult to give one overall tip, but I would say read the instructions for use, because they are all a little different.” She adds, “Make sure to know the basics, like how to hold the pipette, how it functions, and how to care for it.”
In terms of cleaning pipetting tools, it is increasingly common that they can be autoclaved. Nonetheless, Waldroup points out, “Even among those that are autoclavable, the sterilization process can vary in temperature and time.”
Anderson’s key tip about pipetting tools is to make sure “they receive annual service and maintenance by a trained service technician” as pipettes are a precision instrument and will last many years if they are properly cared for.
In a world of next-generation sequencers and PCR seeming simpler than making a box-mix cake, we often forget how far today’s pipette tools have come. The advances, though, mean that these tools need some attention that a rubber bulb from the old days didn’t need. To get the advanced accuracy and repeatability of today’s pipetting tools, scientists must keep them clean and calibrated. Only then can you trust the pipetting in your lab.
For additional resources on planned pipette care, including useful articles and a list of manufacturers, visit www.labmanager.com/pipettes