Typical laboratories have relatively low humidity, meaning greater potential for evaporation and hence inaccurate pipetting compared to the extreme environment of a temperate rain forest
The Artel Extreme Pipetting Expedition announces data showing that pipettes performed accurately and precisely in the humid Olympic National Park yet under-delivered significantly in a drier facility mimicking typical laboratory conditions.
For Mission 4, Artel studied the effect of humidity on pipetted volumes because regulatory standards recommend that pipette calibration take place in facilities with 60 percent relative humidity, while working laboratories commonly operate at 15-40 percent relative humidity.
The data indicate that pipettes calibrated off-site are prone to under-deliver once returned to their usual environments.
Artel is releasing the results from Mission 4 at Pittcon 2008.
"In previous missions, Artel found significant liquid handling error when pipetting in extreme environments with factors such as low barometric pressure and dry heat".
"Now, Artel found almost zero error in the extremely humid Olympic National Park," says George Rodrigues, senior scientific manager, Artel.
"Laboratory managers should consider if their facilities have conditions similar to those at Olympic National Park, with 74 percent relative humidity.
"If not, laboratory data integrity may be at risk".
Pipettes performed well in the humid environment of Olympic National Park due to the low evaporation potential.
A function of both temperature and relative humidity, evaporation potential influences the rate of evaporation.
Greater evaporation occurs in warm environments than in cold environments when relative humidity is held constant, leading to temperature-dependent under-delivery.
The greater the evaporation potential, the more pronounced are pipetting inaccuracy and imprecision.
Rialto Beach in Olympic National Park had a very low evaporation potential (4.5mbar), with a temperature of 14C and relative humidity of 74 percent.
Using the Artel PCS (pipette calibration system), Artel found that pipettes performed extremely well, with average inaccuracy of only -0.35 percent and an average imprecision ratio of 1.33.
Pipettes were also tested at Olympic Inn, with a temperature of 20C and relative humidity of 60 percent - an ideal regulatory specification for pipette calibration laboratories.
Pipettes performed well here, as expected, with average inaccuracy of -0.11 percent and an average imprecision ratio of 0.68.
To quantify the difference in pipette performance in humid environments versus typical working laboratories, Artel pipetted in a laboratory with a temperature of 21C and relative humidity of 22 percent.
Artel found a statistically significant degradation in pipette performance here versus the 60 percent relative humidity environment, with average inaccuracy of -1.55 percent and an average imprecision ratio of 7.10.
These results call into question the performance of pipettes calibrated off-site, such as in a pipette calibration facility, and used in a drier working laboratory.
The data also support the need to calibrate pipettes in the environment in which they are used.
Olympic National Park was chosen as the location for Mission 4 because it is known for its lush, rainforest-like environment.
The park is home to 266 glaciers, over 60 miles of Pacific coastline, and temperate conditions, with over 3.5m of rainfall each year.
The Extreme Pipetting Expedition is a multi-phase, year-long scientific study illustrating the impact of laboratory environmental conditions on pipetting performance and data integrity.
Previous Expedition missions explored how pipetting data integrity is affected by barometric pressure, pipetting warm and cold liquids, and dry heat.
In the future, Artel plans to test pipette performance in actual working laboratories where the environment is believed to have an impact on data, and to offer laboratories concrete guidance on optimising liquid handling operations.
