Pipetting in the extremes

Wednesday, 04 April, 2007

To demonstrate the impact of environmental conditions on pipetted volumes, Artel has launched the Extreme Pipetting Expedition. During this multi-phase, year-long scientific study, Artel will visit locations with extreme ranges of common laboratory conditions, such as high and low temperature, humidity and barometric pressure. Pipette performance will be measured at each location using the Artel PCS (Pipette Calibration System) to identify the resulting volume variability.

The first set of data was collected at Mount Washington, the highest peak in the White Mountains of New Hampshire. At this altitude (1916 m) and lower barometric pressure, the pipettes were found to under-deliver by up to 10%. The data highlight the importance of verifying and calibrating pipettes in actual environmental conditions for optimal laboratory liquid handling operations and accurate data.

"Advancements in liquid handling technology are allowing laboratories to conduct tests and experiments with smaller liquid volumes. However, smaller volumes are more sensitive to volume variation and inaccuracy of just one microlitre can significantly alter results," says Kirby Pilcher, president, Artel. "The objective of Artel's Extreme Pipetting Expedition is to increase awareness of how environmental conditions affect pipetted volume so that laboratories can eliminate a potential source of error and strengthen quality assurance. By testing pipette performance under extreme conditions, we can help pipette users more fully understand how their instruments will perform in a variety of laboratory environments."

To kick off the expedition, Artel trekked to the Mount Washington Weather Observatory situated at an altitude of 1916 m. The facility's barometric pressure measured 805 millibars, well below the sea-level average of 1013 millibars. Data collected by Artel show that at this altitude, air displacement pipettes (the type most commonly used) under-delivered by 1 to 10%, depending on the pipette's make, model and target volume. This volume variation is explained by air's lower density at higher altitudes. Today's laboratories largely rely on air displacement pipettes or liquid handlers to transfer liquid volumes. If air is less dense, less liquid is pulled into the pipette tip and subsequently dispensed, resulting in under-delivery and possible test failure.

Artel's data show that the magnitude of volume variation for each pipette was relatively constant, which facilitates correction within the laboratory. For example, a pipette tested at 10 microlitres under-delivered by 2.6% and 2.8% in replicate tests. Laboratories can compensate for this repeatable volume variation by adjusting the internal mechanism of the pipette for the specific environmental conditions or by adjusting the delivery setting. In this case, because the pipette under-delivered by an average of 2.7%, setting the pipette to deliver 10.27 microlitres would deliver an actual volume of 10 microlitres.

"The preliminary data show the importance of regularly verifying pipettes in the environment in which they are used," says George Rodrigues, PhD, senior scientific manager. "Consider a laboratory in Denver or Mexico City that sends pipettes to a laboratory at sea-level for calibration. Even newly calibrated, the pipettes would likely under-deliver once back in the laboratory and produce inaccurate data."

The Artel PCS was used to measure the performance of three different pipettes in the extreme conditions of Mount Washington. The same pipettes were verified using the PCS in Artel's ISO-certified test laboratory under normal, controlled conditions at sea-level.

To isolate barometric pressure as the source of volume variability, Artel controlled for other sources of error, including operator technique, temperature, humidity, the measuring method and pipette failure.

A robust, portable system, PCS is unaffected by environmental conditions. The PCS also provides standardised, traceable results for a scientifically sound comparison of data regardless of the environment in which data are taken or pipettes are used.

For complete experiment parameters and a summary of test data, visit www.artel-usa.com/extreme. This website will be updated regularly with data from new Extreme Pipetting locations, new insights into the effects of environmental conditions on pipettes and stories from scientists in the field.

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