Precise and repeated dispensing of small and large volumes of liquids is central to ‘wet lab research’ in biological laboratories. Over the past few decades wet lab research has become increasingly fast-paced and hi-tech, covering the spectrum between low and high throughput assays that bank on the quick and accurate transfer of milliliter to sub-microliter volumes of diverse liquid samples and reagents. The manual pipette is therefore a universal fixture in all wet labs.
A number of errors can creep into your experiment during liquid handing that can be classified into systematic errors (accuracy) that measure how close the volume measured is to the desired reading, and random errors (precision) that measure how close the dispensed volume is to other dispensations of the same reading, assessing the reproducibility of the device1. A specific measure of transferred liquid can contribute to both systematic and random errors.
Factors Impacting Pipetting
Just like a magnificent rendition of Mozart by a world famous symphony can be ruined by an erring cell phone, the masterful accuracy and precision of the best pipettes can be compromised by a rise in the temperature, the angle at which you tilt the tip in the reagent, the force and speed with which you press and release the plunger, failing to consider the physical properties of the liquid, or a wobbly tip at the pipette’s nose. Given the high frequency of liquid handling in any wet lab, and the virtual impossibility of detecting miniscule discrepancies between individual pipetting dispensations by the naked eye that can have a significant impact on your results, it is crucial to take precautions against potential sources of variability rather than rectify a problem post hoc. An overlooked variable can result in expensive re-do’s, loss of precious samples and reagents, and irrecoverable delays.
