Manual Liquid Handling Focuses on Ergonomics
It is not much of a stretch to say that the 1961 introduction of the plunger-operated pipette revolutionized laboratory work. The obvious improvements over hand-operated, bulb-type pipettes were repeatability, accuracy, and the ability to deliver extremely small volumes of liquid reproducibly.
These advantages came at a cost, however. The high-throughput demands of modern laboratories have led to a rise in pipette-related repetitive stress injuries (RSIs). In a worst-case scenario, RSIs can lead to surgery and lost productivity costing tens of thousands of dollars.
Improved ergonomics is therefore the most easily identifiable trend in pipettes. Materials used to manufacture pipettes have become lighter, and draw/dispense mechanisms easier to actuate.
According to Andrea Dickstein, director of marketing at Eppendorf (Hauppauge, NY), preventing RSIs should be a top priority in highthroughput labs. “Preventive measures are the best defense against RSIs,” she says. “Postures, positions, and activities that cause discomfort should be modified or spaced out over time.”
Dickstein provides the following tips for selecting and using pipettes:
- Make sure the pipette fits well in the hand.
- Determine that the volume is easily adjustable and that all buttons are easily accessible.
- Choose a pipette whose plunger mechanism requires low activation force.
- Make sure the operator’s hand can flex without removing the pipette.
- When using a pipette for more than two hours a day, choose an electronic pipette for high-throughput needs, or multichannel pipettes for microtiter plate applications.
- Consider automating through a liquid- handling workstation.
Christian Petrilli, director of marketing at BrandTech Scientific (Essex, CT), believes that pipette ergonomics comes down to ease of use. “Are the various pipette operations intuitive? Does [the pipette] feel comfortable in your hand? Are its functions accessible and obvious?”
Materials make a difference in more than ergonomics. Today’s best pipettes are made from space-age materials that are not only light, but also resist chemical, thermal, and mechanical stresses. Since many pipettes in use today operate with biological materials, cleanability is a must-have feature to prevent cross-contamination. Pipette surfaces should be fully cleanable with water, disinfectants, and appropriate solvents. Many pipettes are autoclavable, meaning they can be steam-sterilized to kill pathogens. (Note that autoclavable pipettes must still be wiped down or cleaned, however.)
Electronic pipettes are becoming more popular because of the reduction in sample volumes and simultaneous increase in the number of samples processed—particularly through microtiter plates. Electronic pipettes, which are considered a halfway point between manual and robotic liquid handling, offer advantages of high reproducibility, a reduction in the force necessary for operation, and multi-functionality in dispensing techniques. Dickstein says, “Electronic pipettes go beyond the capabilities of standard pipettes while minimizing strains associated with standard mechanical pipettes, [thereby] improving ergonomics.”
Calibration is perhaps the most important service-related activity for pipettes. Calibration ensures that the pipette is delivering precise volumes after thousands of cycles. Regulated industries calibrate their instruments several times a year: all labs using pipettes should consider taking advantage of calibration services every six to twelve months.
Some pipettes may be calibrated by the user, but most calibrations are carried out at the original manufacturer’s facility or, as in the case of BrandTech products, through a thirdparty service provider. Some service companies perform calibration at the customer’s site.
Calibration is conducted by dispensing volumes of water and weighing them on an analytical balance. Calibration usually takes place off-site at the calibrator’s facility, under conditions of strict environmental control and using standardized methods and materials. For example, Eppendorf employs a weighing vessel and a trap to reduce evaporation from small samples. The company’s calibration room is maintained at 50 percent relative humidity and a constant temperature. Water used during testing is degassed and distilled; technicians test three different volumes for variable-volume pipettes; and all volumes are measured at least ten times.
A typical calibration costs between $20 and $100 per pipette. Off-site calibration has a turnaround time of two days, while on-site calibration can be done the same day.
Like most routine maintenance, calibration may be viewed as more of an inconvenience than a necessity. “Some users are less concerned about the quality of calibration than about getting a sticker on their pipette that says it’s been calibrated,” says Petrilli, “but most recognize the value of a pipette that is calibrated properly. Certainly anyone in a regulated environment knows the importance of calibration.”
Dickstein adds, “A pipette needs to be thought of as a precision instrument. That’s why being certain it is performing as intended by the manufacturer is so critical. Calibration ensures these standards are met.”
For additional resources on pipettes, including useful articles and a list of manufacturers, visit www.labmanager.com/pipettes
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